Remove default MD5 in most of Bazel's virtual filesystems.

This forces the ex-default to be explicit in a lot of tests, but I'd rather that than have the risk of implicit md5-use in production code.

To keep this CL smaller, do not remove the default from UnixFS quite yet.

RELNOTES: None.
PiperOrigin-RevId: 206223521

63 files changed, 197 insertions, 124 deletions

diff --git a/src/test/java/com/google/devtools/build/lib/actions/DigestUtilsTest.java b/src/test/java/com/google/devtools/build/lib/actions/DigestUtilsTest.java
index fc6376e46f..9a06fd4743 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/DigestUtilsTest.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/DigestUtilsTest.java
@@ -224,7 +224,7 @@ public class DigestUtilsTest {
     final AtomicInteger getDigestCounter = new AtomicInteger(0);
 
     FileSystem tracingFileSystem =
-        new InMemoryFileSystem(BlazeClock.instance()) {
+        new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5) {
           @Override
           protected byte[] getFastDigest(Path path) throws IOException {
             getFastDigestCounter.incrementAndGet();
diff --git a/src/test/java/com/google/devtools/build/lib/actions/MapBasedActionGraphTest.java b/src/test/java/com/google/devtools/build/lib/actions/MapBasedActionGraphTest.java
index 5de14d956c..a658a8146e 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/MapBasedActionGraphTest.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/MapBasedActionGraphTest.java
@@ -21,6 +21,7 @@ import com.google.devtools.build.lib.actions.util.ActionsTestUtil.UncheckedActio
 import com.google.devtools.build.lib.actions.util.TestAction;
 import com.google.devtools.build.lib.concurrent.AbstractQueueVisitor;
 import com.google.devtools.build.lib.concurrent.ErrorClassifier;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
@@ -36,7 +37,7 @@ import org.junit.runners.JUnit4;
  */
 @RunWith(JUnit4.class)
 public class MapBasedActionGraphTest {
-  private final FileSystem fileSystem = new InMemoryFileSystem();
+  private final FileSystem fileSystem = new InMemoryFileSystem(DigestHashFunction.MD5);
   private final ActionKeyContext actionKeyContext = new ActionKeyContext();
 
   @Test
diff --git a/src/test/java/com/google/devtools/build/lib/actions/util/ActionsTestUtil.java b/src/test/java/com/google/devtools/build/lib/actions/util/ActionsTestUtil.java
index cd3489ddf5..ec13e93cdb 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/util/ActionsTestUtil.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/util/ActionsTestUtil.java
@@ -69,6 +69,7 @@ import com.google.devtools.build.lib.util.FileType;
 import com.google.devtools.build.lib.util.Fingerprint;
 import com.google.devtools.build.lib.util.ResourceUsage;
 import com.google.devtools.build.lib.util.io.FileOutErr;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileStatus;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
@@ -258,7 +259,8 @@ public final class ActionsTestUtil {
   public static final Artifact DUMMY_ARTIFACT =
       new Artifact(
           PathFragment.create("/dummy"),
-          ArtifactRoot.asSourceRoot(Root.absoluteRoot(new InMemoryFileSystem())));
+          ArtifactRoot.asSourceRoot(
+              Root.absoluteRoot(new InMemoryFileSystem(DigestHashFunction.MD5))));
 
   public static final ActionOwner NULL_ACTION_OWNER =
       ActionOwner.create(
diff --git a/src/test/java/com/google/devtools/build/lib/analysis/AnalysisWithIOExceptionsTest.java b/src/test/java/com/google/devtools/build/lib/analysis/AnalysisWithIOExceptionsTest.java
index 67d9b6254a..6273c9816a 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/AnalysisWithIOExceptionsTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/AnalysisWithIOExceptionsTest.java
@@ -17,6 +17,7 @@ import static org.junit.Assert.fail;
 
 import com.google.devtools.build.lib.analysis.util.AnalysisTestCase;
 import com.google.devtools.build.lib.clock.BlazeClock;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileStatus;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
@@ -36,7 +37,7 @@ public class AnalysisWithIOExceptionsTest extends AnalysisTestCase {
 
   @Override
   protected FileSystem createFileSystem() {
-    return new InMemoryFileSystem(BlazeClock.instance()) {
+    return new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5) {
       @Override
       public FileStatus stat(Path path, boolean followSymlinks) throws IOException {
         String crash = crashMessage.apply(path);
diff --git a/src/test/java/com/google/devtools/build/lib/analysis/InterruptedExceptionTest.java b/src/test/java/com/google/devtools/build/lib/analysis/InterruptedExceptionTest.java
index fc1b7078e6..8afbf2d86d 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/InterruptedExceptionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/InterruptedExceptionTest.java
@@ -17,6 +17,7 @@ import static org.junit.Assert.fail;
 
 import com.google.devtools.build.lib.analysis.util.AnalysisTestCase;
 import com.google.devtools.build.lib.clock.BlazeClock;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.Dirent;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
@@ -38,7 +39,7 @@ public class InterruptedExceptionTest extends AnalysisTestCase {
 
   @Override
   protected FileSystem createFileSystem() {
-    return new InMemoryFileSystem(BlazeClock.instance()) {
+    return new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5) {
       @Override
       protected Collection<Dirent> readdir(Path path, boolean followSymlinks) throws IOException {
         if (path.toString().contains("causes_interrupt")) {
diff --git a/src/test/java/com/google/devtools/build/lib/analysis/LocationFunctionTest.java b/src/test/java/com/google/devtools/build/lib/analysis/LocationFunctionTest.java
index 258095fa95..37b870d9b1 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/LocationFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/LocationFunctionTest.java
@@ -24,6 +24,7 @@ import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.LocationExpander.LocationFunction;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.cmdline.RepositoryName;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Root;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
@@ -196,7 +197,7 @@ final class LocationFunctionBuilder {
   }
 
   private static Artifact makeArtifact(String path) {
-    FileSystem fs = new InMemoryFileSystem();
+    FileSystem fs = new InMemoryFileSystem(DigestHashFunction.MD5);
     if (path.startsWith("/exec/out")) {
       return new Artifact(
           fs.getPath(path),
diff --git a/src/test/java/com/google/devtools/build/lib/bazel/repository/DecompressorValueTest.java b/src/test/java/com/google/devtools/build/lib/bazel/repository/DecompressorValueTest.java
index 67616fa683..d31a5fbc5f 100644
--- a/src/test/java/com/google/devtools/build/lib/bazel/repository/DecompressorValueTest.java
+++ b/src/test/java/com/google/devtools/build/lib/bazel/repository/DecompressorValueTest.java
@@ -18,6 +18,7 @@ import static com.google.common.truth.Truth.assertThat;
 import static org.junit.Assert.fail;
 
 import com.google.devtools.build.lib.rules.repository.RepositoryFunction.RepositoryFunctionException;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
@@ -31,7 +32,7 @@ import org.junit.runners.JUnit4;
 @RunWith(JUnit4.class)
 public class DecompressorValueTest {
 
-  private FileSystem fs = new InMemoryFileSystem();
+  private FileSystem fs = new InMemoryFileSystem(DigestHashFunction.MD5);
 
   @Test
   public void testKnownFileExtensionsDoNotThrow() throws Exception {
diff --git a/src/test/java/com/google/devtools/build/lib/buildtool/SymlinkForestTest.java b/src/test/java/com/google/devtools/build/lib/buildtool/SymlinkForestTest.java
index ab550a072d..1626cd47b2 100644
--- a/src/test/java/com/google/devtools/build/lib/buildtool/SymlinkForestTest.java
+++ b/src/test/java/com/google/devtools/build/lib/buildtool/SymlinkForestTest.java
@@ -25,6 +25,7 @@ import com.google.devtools.build.lib.cmdline.PackageIdentifier;
 import com.google.devtools.build.lib.cmdline.RepositoryName;
 import com.google.devtools.build.lib.testutil.ManualClock;
 import com.google.devtools.build.lib.testutil.TestConstants;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
@@ -56,7 +57,7 @@ public class SymlinkForestTest {
   @Before
   public final void initializeFileSystem() throws Exception {
     ManualClock clock = new ManualClock();
-    fileSystem = new InMemoryFileSystem(clock);
+    fileSystem = new InMemoryFileSystem(clock, DigestHashFunction.MD5);
     linkRoot = fileSystem.getPath("/linkRoot");
     createDirectoryAndParents(linkRoot);
   }
diff --git a/src/test/java/com/google/devtools/build/lib/exec/AbstractSpawnStrategyTest.java b/src/test/java/com/google/devtools/build/lib/exec/AbstractSpawnStrategyTest.java
index d92a1b155e..1ea3935748 100644
--- a/src/test/java/com/google/devtools/build/lib/exec/AbstractSpawnStrategyTest.java
+++ b/src/test/java/com/google/devtools/build/lib/exec/AbstractSpawnStrategyTest.java
@@ -40,6 +40,7 @@ import com.google.devtools.build.lib.testutil.Scratch;
 import com.google.devtools.build.lib.testutil.Suite;
 import com.google.devtools.build.lib.testutil.TestSpec;
 import com.google.devtools.build.lib.util.io.MessageOutputStream;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.Root;
@@ -65,7 +66,7 @@ public class AbstractSpawnStrategyTest {
   private static final Spawn SIMPLE_SPAWN =
       new SpawnBuilder("/bin/echo", "Hi!").withEnvironment("VARIABLE", "value").build();
 
-  private final FileSystem fs = new InMemoryFileSystem();
+  private final FileSystem fs = new InMemoryFileSystem(DigestHashFunction.MD5);
   private final Path execRoot = fs.getPath("/execroot");
   private Scratch scratch;
   private ArtifactRoot rootDir;
diff --git a/src/test/java/com/google/devtools/build/lib/exec/BlazeExecutorTest.java b/src/test/java/com/google/devtools/build/lib/exec/BlazeExecutorTest.java
index 1dcd3b0e11..0390a01a80 100644
--- a/src/test/java/com/google/devtools/build/lib/exec/BlazeExecutorTest.java
+++ b/src/test/java/com/google/devtools/build/lib/exec/BlazeExecutorTest.java
@@ -27,6 +27,7 @@ import com.google.devtools.build.lib.events.StoredEventHandler;
 import com.google.devtools.build.lib.exec.util.TestExecutorBuilder;
 import com.google.devtools.build.lib.testutil.Suite;
 import com.google.devtools.build.lib.testutil.TestSpec;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
 import com.google.devtools.common.options.OptionsParser;
@@ -47,7 +48,7 @@ public class BlazeExecutorTest {
 
   @Before
   public final void setUpDirectoriesAndTools() throws Exception {
-    fileSystem = new InMemoryFileSystem();
+    fileSystem = new InMemoryFileSystem(DigestHashFunction.MD5);
     directories =
         new BlazeDirectories(
             new ServerDirectories(
diff --git a/src/test/java/com/google/devtools/build/lib/exec/FilesetManifestTest.java b/src/test/java/com/google/devtools/build/lib/exec/FilesetManifestTest.java
index 2db666eb19..7906788e53 100644
--- a/src/test/java/com/google/devtools/build/lib/exec/FilesetManifestTest.java
+++ b/src/test/java/com/google/devtools/build/lib/exec/FilesetManifestTest.java
@@ -21,6 +21,7 @@ import static org.junit.Assert.fail;
 
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.ArtifactRoot;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
@@ -44,7 +45,7 @@ public class FilesetManifestTest {
 
   @Before
   public final void createSpawnInputExpander() throws Exception  {
-    fs = new InMemoryFileSystem();
+    fs = new InMemoryFileSystem(DigestHashFunction.MD5);
     execRoot = fs.getPath("/root");
   }
 
diff --git a/src/test/java/com/google/devtools/build/lib/exec/SingleBuildFileCacheTest.java b/src/test/java/com/google/devtools/build/lib/exec/SingleBuildFileCacheTest.java
index c3fa2dbc4b..4b054a795e 100644
--- a/src/test/java/com/google/devtools/build/lib/exec/SingleBuildFileCacheTest.java
+++ b/src/test/java/com/google/devtools/build/lib/exec/SingleBuildFileCacheTest.java
@@ -57,7 +57,7 @@ public class SingleBuildFileCacheTest {
     calls = new HashMap<>();
     md5Overrides = new HashMap<>();
     fs =
-        new InMemoryFileSystem() {
+        new InMemoryFileSystem(DigestHashFunction.MD5) {
           @Override
           protected InputStream getInputStream(Path path) throws IOException {
             int c = calls.containsKey(path.toString()) ? calls.get(path.toString()) : 0;
diff --git a/src/test/java/com/google/devtools/build/lib/exec/SpawnInputExpanderTest.java b/src/test/java/com/google/devtools/build/lib/exec/SpawnInputExpanderTest.java
index e21fdbb4e8..f8b59a07f5 100644
--- a/src/test/java/com/google/devtools/build/lib/exec/SpawnInputExpanderTest.java
+++ b/src/test/java/com/google/devtools/build/lib/exec/SpawnInputExpanderTest.java
@@ -33,6 +33,7 @@ import com.google.devtools.build.lib.actions.RunfilesSupplier;
 import com.google.devtools.build.lib.analysis.Runfiles;
 import com.google.devtools.build.lib.analysis.RunfilesSupplierImpl;
 import com.google.devtools.build.lib.exec.util.FakeActionInputFileCache;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
@@ -62,7 +63,7 @@ public class SpawnInputExpanderTest {
 
   @Before
   public final void createSpawnInputExpander() throws Exception  {
-    fs = new InMemoryFileSystem();
+    fs = new InMemoryFileSystem(DigestHashFunction.MD5);
     execRoot = fs.getPath("/root");
     expander = new SpawnInputExpander(execRoot, /*strict=*/ true);
     inputMappings = Maps.newHashMap();
diff --git a/src/test/java/com/google/devtools/build/lib/exec/SymlinkTreeHelperTest.java b/src/test/java/com/google/devtools/build/lib/exec/SymlinkTreeHelperTest.java
index 808fe36027..2e25907160 100644
--- a/src/test/java/com/google/devtools/build/lib/exec/SymlinkTreeHelperTest.java
+++ b/src/test/java/com/google/devtools/build/lib/exec/SymlinkTreeHelperTest.java
@@ -24,6 +24,7 @@ import com.google.devtools.build.lib.actions.ActionInputHelper;
 import com.google.devtools.build.lib.actions.ExecutionRequirements;
 import com.google.devtools.build.lib.actions.Spawn;
 import com.google.devtools.build.lib.exec.util.FakeOwner;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
@@ -34,7 +35,7 @@ import org.junit.runners.JUnit4;
 /** Unit tests for {@link SymlinkTreeHelper}. */
 @RunWith(JUnit4.class)
 public final class SymlinkTreeHelperTest {
-  private final FileSystem fs = new InMemoryFileSystem();
+  private final FileSystem fs = new InMemoryFileSystem(DigestHashFunction.MD5);
 
   @Test
   public void checkCreatedSpawn() {
diff --git a/src/test/java/com/google/devtools/build/lib/exec/local/LocalSpawnRunnerTest.java b/src/test/java/com/google/devtools/build/lib/exec/local/LocalSpawnRunnerTest.java
index 35f7365afa..e4fc2bcc69 100644
--- a/src/test/java/com/google/devtools/build/lib/exec/local/LocalSpawnRunnerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/exec/local/LocalSpawnRunnerTest.java
@@ -54,6 +54,7 @@ import com.google.devtools.build.lib.unix.UnixFileSystem;
 import com.google.devtools.build.lib.util.NetUtil;
 import com.google.devtools.build.lib.util.OS;
 import com.google.devtools.build.lib.util.io.FileOutErr;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
@@ -273,7 +274,7 @@ public class LocalSpawnRunnerTest {
     SubprocessBuilder.setSubprocessFactory(new SubprocessInterceptor());
     resourceManager.setAvailableResources(
         ResourceSet.create(/*memoryMb=*/1, /*cpuUsage=*/1, /*ioUsage=*/1, /*localTestCount=*/1));
-    return new InMemoryFileSystem();
+    return new InMemoryFileSystem(DigestHashFunction.MD5);
   }
 
   /**
diff --git a/src/test/java/com/google/devtools/build/lib/packages/util/PackageFactoryTestBase.java b/src/test/java/com/google/devtools/build/lib/packages/util/PackageFactoryTestBase.java
index eb614fc49c..7b9de78167 100644
--- a/src/test/java/com/google/devtools/build/lib/packages/util/PackageFactoryTestBase.java
+++ b/src/test/java/com/google/devtools/build/lib/packages/util/PackageFactoryTestBase.java
@@ -36,6 +36,7 @@ import com.google.devtools.build.lib.syntax.Printer;
 import com.google.devtools.build.lib.testutil.Scratch;
 import com.google.devtools.build.lib.testutil.TestUtils;
 import com.google.devtools.build.lib.util.Pair;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.Dirent;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
@@ -120,7 +121,7 @@ public abstract class PackageFactoryTestBase {
   @Before
   public final void initializeFileSystem() throws Exception {
     FileSystem fs =
-        new InMemoryFileSystem() {
+        new InMemoryFileSystem(DigestHashFunction.MD5) {
           @Override
           public Collection<Dirent> readdir(Path path, boolean followSymlinks) throws IOException {
             if (path.equals(throwOnReaddir)) {
diff --git a/src/test/java/com/google/devtools/build/lib/pkgcache/BuildFileModificationTest.java b/src/test/java/com/google/devtools/build/lib/pkgcache/BuildFileModificationTest.java
index 2890619c2e..3b57806ab6 100644
--- a/src/test/java/com/google/devtools/build/lib/pkgcache/BuildFileModificationTest.java
+++ b/src/test/java/com/google/devtools/build/lib/pkgcache/BuildFileModificationTest.java
@@ -37,6 +37,7 @@ import com.google.devtools.build.lib.testutil.FoundationTestCase;
 import com.google.devtools.build.lib.testutil.ManualClock;
 import com.google.devtools.build.lib.testutil.TestConstants;
 import com.google.devtools.build.lib.util.io.TimestampGranularityMonitor;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.ModifiedFileSet;
@@ -134,7 +135,7 @@ public class BuildFileModificationTest extends FoundationTestCase {
 
   @Override
   protected FileSystem createFileSystem() {
-    return new InMemoryFileSystem(clock);
+    return new InMemoryFileSystem(clock, DigestHashFunction.MD5);
   }
 
   private void invalidatePackages() throws InterruptedException {
diff --git a/src/test/java/com/google/devtools/build/lib/pkgcache/IOExceptionsTest.java b/src/test/java/com/google/devtools/build/lib/pkgcache/IOExceptionsTest.java
index de8e71b221..fdd96234ed 100644
--- a/src/test/java/com/google/devtools/build/lib/pkgcache/IOExceptionsTest.java
+++ b/src/test/java/com/google/devtools/build/lib/pkgcache/IOExceptionsTest.java
@@ -24,6 +24,7 @@ import com.google.devtools.build.lib.packages.ConstantRuleVisibility;
 import com.google.devtools.build.lib.packages.util.PackageLoadingTestCase;
 import com.google.devtools.build.lib.skyframe.TransitiveTargetKey;
 import com.google.devtools.build.lib.skyframe.TransitiveTargetValue;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileStatus;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.ModifiedFileSet;
@@ -82,7 +83,8 @@ public class IOExceptionsTest extends PackageLoadingTestCase {
 
   @Override
   protected FileSystem createFileSystem() {
-    return new InMemoryFileSystem(BlazeClock.instance(), PathFragment.create(FS_ROOT)) {
+    return new InMemoryFileSystem(
+        BlazeClock.instance(), PathFragment.create(FS_ROOT), DigestHashFunction.MD5) {
       @Override
       public FileStatus stat(Path path, boolean followSymlinks) throws IOException {
         String crash = crashMessage.apply(path);
diff --git a/src/test/java/com/google/devtools/build/lib/pkgcache/IncrementalLoadingTest.java b/src/test/java/com/google/devtools/build/lib/pkgcache/IncrementalLoadingTest.java
index 866844df31..e6cb8562b1 100644
--- a/src/test/java/com/google/devtools/build/lib/pkgcache/IncrementalLoadingTest.java
+++ b/src/test/java/com/google/devtools/build/lib/pkgcache/IncrementalLoadingTest.java
@@ -46,6 +46,7 @@ import com.google.devtools.build.lib.skyframe.SkyframeExecutor;
 import com.google.devtools.build.lib.testutil.ManualClock;
 import com.google.devtools.build.lib.testutil.TestConstants;
 import com.google.devtools.build.lib.util.io.TimestampGranularityMonitor;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.Dirent;
 import com.google.devtools.build.lib.vfs.FileStatus;
 import com.google.devtools.build.lib.vfs.FileSystem;
@@ -86,7 +87,7 @@ public class IncrementalLoadingTest {
   public final void createTester() throws Exception {
     ManualClock clock = new ManualClock();
     FileSystem fs =
-        new InMemoryFileSystem(clock) {
+        new InMemoryFileSystem(clock, DigestHashFunction.MD5) {
           @Override
           public Collection<Dirent> readdir(Path path, boolean followSymlinks) throws IOException {
             if (path.equals(throwOnReaddir)) {
diff --git a/src/test/java/com/google/devtools/build/lib/pkgcache/LoadingPhaseRunnerTest.java b/src/test/java/com/google/devtools/build/lib/pkgcache/LoadingPhaseRunnerTest.java
index 50e6ecf0e6..d2039af36f 100644
--- a/src/test/java/com/google/devtools/build/lib/pkgcache/LoadingPhaseRunnerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/pkgcache/LoadingPhaseRunnerTest.java
@@ -55,6 +55,7 @@ import com.google.devtools.build.lib.testutil.ManualClock;
 import com.google.devtools.build.lib.testutil.MoreAsserts;
 import com.google.devtools.build.lib.testutil.TestConstants;
 import com.google.devtools.build.lib.util.io.TimestampGranularityMonitor;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.ModifiedFileSet;
@@ -715,7 +716,7 @@ public class LoadingPhaseRunnerTest {
     private MockToolsConfig mockToolsConfig;
 
     public LoadingPhaseTester() throws IOException {
-      FileSystem fs = new InMemoryFileSystem(clock);
+      FileSystem fs = new InMemoryFileSystem(clock, DigestHashFunction.MD5);
       this.workspace = fs.getPath("/workspace");
       workspace.createDirectory();
       mockToolsConfig = new MockToolsConfig(workspace);
diff --git a/src/test/java/com/google/devtools/build/lib/pkgcache/TargetPatternEvaluatorIOTest.java b/src/test/java/com/google/devtools/build/lib/pkgcache/TargetPatternEvaluatorIOTest.java
index f2a7233b69..1f0bb9d86a 100644
--- a/src/test/java/com/google/devtools/build/lib/pkgcache/TargetPatternEvaluatorIOTest.java
+++ b/src/test/java/com/google/devtools/build/lib/pkgcache/TargetPatternEvaluatorIOTest.java
@@ -17,6 +17,7 @@ import com.google.common.collect.ImmutableSet;
 import com.google.common.truth.Truth;
 import com.google.devtools.build.lib.clock.BlazeClock;
 import com.google.devtools.build.lib.events.EventKind;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.Dirent;
 import com.google.devtools.build.lib.vfs.FileStatus;
 import com.google.devtools.build.lib.vfs.FileSystem;
@@ -57,7 +58,8 @@ public class TargetPatternEvaluatorIOTest extends AbstractTargetPatternEvaluator
 
   @Override
   protected FileSystem createFileSystem() {
-    return new InMemoryFileSystem(BlazeClock.instance(), PathFragment.create(FS_ROOT)) {
+    return new InMemoryFileSystem(
+        BlazeClock.instance(), PathFragment.create(FS_ROOT), DigestHashFunction.MD5) {
       @Override
       public FileStatus stat(Path path, boolean followSymlinks) throws IOException {
         FileStatus defaultResult = super.stat(path, followSymlinks);
diff --git a/src/test/java/com/google/devtools/build/lib/profiler/AutoProfilerBenchmark.java b/src/test/java/com/google/devtools/build/lib/profiler/AutoProfilerBenchmark.java
index 044ae8c0d4..1022f38d92 100644
--- a/src/test/java/com/google/devtools/build/lib/profiler/AutoProfilerBenchmark.java
+++ b/src/test/java/com/google/devtools/build/lib/profiler/AutoProfilerBenchmark.java
@@ -17,6 +17,7 @@ import com.google.caliper.BeforeExperiment;
 import com.google.caliper.Benchmark;
 import com.google.devtools.build.lib.clock.BlazeClock;
 import com.google.devtools.build.lib.profiler.Profiler.ProfiledTaskKinds;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
 
 /**
@@ -27,14 +28,15 @@ public class AutoProfilerBenchmark {
 
   @BeforeExperiment
   void startProfiler() throws Exception {
-    Profiler.instance().start(
-        ProfiledTaskKinds.ALL,
-        new InMemoryFileSystem().getPath("/out.dat").getOutputStream(),
-        Profiler.Format.BINARY_BAZEL_FORMAT,
-        "benchmark",
-        false,
-        BlazeClock.instance(),
-        BlazeClock.instance().nanoTime());
+    Profiler.instance()
+        .start(
+            ProfiledTaskKinds.ALL,
+            new InMemoryFileSystem(DigestHashFunction.MD5).getPath("/out.dat").getOutputStream(),
+            Profiler.Format.BINARY_BAZEL_FORMAT,
+            "benchmark",
+            false,
+            BlazeClock.instance(),
+            BlazeClock.instance().nanoTime());
   }
 
   @BeforeExperiment
diff --git a/src/test/java/com/google/devtools/build/lib/rules/android/ResourceTestBase.java b/src/test/java/com/google/devtools/build/lib/rules/android/ResourceTestBase.java
index dad6ee04fe..2eabbba2d3 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/android/ResourceTestBase.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/android/ResourceTestBase.java
@@ -36,6 +36,7 @@ import com.google.devtools.build.lib.events.StoredEventHandler;
 import com.google.devtools.build.lib.packages.AbstractRuleErrorConsumer;
 import com.google.devtools.build.lib.packages.RuleErrorConsumer;
 import com.google.devtools.build.lib.skyframe.ConfiguredTargetKey;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.Root;
@@ -184,7 +185,7 @@ public abstract class ResourceTestBase extends AndroidBuildViewTestCase {
   @Before
   public void setup() {
     errorConsumer = new FakeRuleErrorConsumer();
-    fileSystem = new InMemoryFileSystem();
+    fileSystem = new InMemoryFileSystem(DigestHashFunction.MD5);
     root = ArtifactRoot.asSourceRoot(Root.fromPath(fileSystem.getPath("/")));
   }
 
diff --git a/src/test/java/com/google/devtools/build/lib/rules/cpp/HeaderDiscoveryTest.java b/src/test/java/com/google/devtools/build/lib/rules/cpp/HeaderDiscoveryTest.java
index 831cf95350..105b8f7b82 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/cpp/HeaderDiscoveryTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/cpp/HeaderDiscoveryTest.java
@@ -26,6 +26,7 @@ import com.google.devtools.build.lib.actions.ArtifactResolver;
 import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.util.ActionsTestUtil;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
@@ -37,7 +38,7 @@ import org.junit.runners.JUnit4;
 @RunWith(JUnit4.class)
 public class HeaderDiscoveryTest {
 
-  private final FileSystem fs = new InMemoryFileSystem();
+  private final FileSystem fs = new InMemoryFileSystem(DigestHashFunction.MD5);
   private final Path execRoot = fs.getPath("/execroot");
   private final Path derivedRoot = execRoot.getRelative("derived");
   private final ArtifactRoot artifactRoot = ArtifactRoot.asDerivedRoot(execRoot, derivedRoot);
diff --git a/src/test/java/com/google/devtools/build/lib/rules/cpp/ShowIncludesFilterTest.java b/src/test/java/com/google/devtools/build/lib/rules/cpp/ShowIncludesFilterTest.java
index 2a55081e99..72424d092f 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/cpp/ShowIncludesFilterTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/cpp/ShowIncludesFilterTest.java
@@ -18,6 +18,7 @@ import static com.google.common.truth.Truth.assertThat;
 import static java.nio.charset.StandardCharsets.UTF_8;
 
 import com.google.devtools.build.lib.util.io.FileOutErr;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
 import java.io.ByteArrayOutputStream;
@@ -43,7 +44,7 @@ public class ShowIncludesFilterTest {
     showIncludesFilter = new ShowIncludesFilter("foo.cpp");
     output = new ByteArrayOutputStream();
     filterOutputStream = showIncludesFilter.getFilteredOutputStream(output);
-    fs = new InMemoryFileSystem();
+    fs = new InMemoryFileSystem(DigestHashFunction.MD5);
     fs.getPath("/out").createDirectory();
   }
 
diff --git a/src/test/java/com/google/devtools/build/lib/rules/proto/ProtoCompileActionBuilderTest.java b/src/test/java/com/google/devtools/build/lib/rules/proto/ProtoCompileActionBuilderTest.java
index 1e2311fa84..5edf6807ff 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/proto/ProtoCompileActionBuilderTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/proto/ProtoCompileActionBuilderTest.java
@@ -34,6 +34,7 @@ import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
 import com.google.devtools.build.lib.collect.nestedset.Order;
 import com.google.devtools.build.lib.rules.proto.ProtoCompileActionBuilder.ToolchainInvocation;
 import com.google.devtools.build.lib.util.LazyString;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.Root;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
 import javax.annotation.Nullable;
@@ -45,7 +46,8 @@ import org.junit.runners.JUnit4;
 @RunWith(JUnit4.class)
 public class ProtoCompileActionBuilderTest {
 
-  private static final InMemoryFileSystem FILE_SYSTEM = new InMemoryFileSystem();
+  private static final InMemoryFileSystem FILE_SYSTEM =
+      new InMemoryFileSystem(DigestHashFunction.MD5);
   private final ArtifactRoot root =
       ArtifactRoot.asSourceRoot(Root.fromPath(FILE_SYSTEM.getPath("/")));
   private final ArtifactRoot derivedRoot =
diff --git a/src/test/java/com/google/devtools/build/lib/runtime/ProcessWrapperUtilTest.java b/src/test/java/com/google/devtools/build/lib/runtime/ProcessWrapperUtilTest.java
index ff1fdd50d5..adefde3b0c 100644
--- a/src/test/java/com/google/devtools/build/lib/runtime/ProcessWrapperUtilTest.java
+++ b/src/test/java/com/google/devtools/build/lib/runtime/ProcessWrapperUtilTest.java
@@ -17,6 +17,7 @@ package com.google.devtools.build.lib.runtime;
 import static com.google.common.truth.Truth.assertThat;
 
 import com.google.common.collect.ImmutableList;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
@@ -34,7 +35,7 @@ public final class ProcessWrapperUtilTest {
 
   @Before
   public final void createFileSystem() {
-    testFS = new InMemoryFileSystem();
+    testFS = new InMemoryFileSystem(DigestHashFunction.MD5);
   }
 
   @Test
diff --git a/src/test/java/com/google/devtools/build/lib/runtime/TestSummaryTest.java b/src/test/java/com/google/devtools/build/lib/runtime/TestSummaryTest.java
index ee0f08c041..a033517d35 100644
--- a/src/test/java/com/google/devtools/build/lib/runtime/TestSummaryTest.java
+++ b/src/test/java/com/google/devtools/build/lib/runtime/TestSummaryTest.java
@@ -29,6 +29,7 @@ import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
 import com.google.devtools.build.lib.clock.BlazeClock;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.util.io.AnsiTerminalPrinter;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
@@ -63,7 +64,7 @@ public class TestSummaryTest {
 
   @Before
   public final void createFileSystem() throws Exception  {
-    fs = new InMemoryFileSystem(BlazeClock.instance());
+    fs = new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5);
     stubTarget = stubTarget();
     basicBuilder = getTemplateBuilder();
   }
diff --git a/src/test/java/com/google/devtools/build/lib/sandbox/FakeSandboxfsProcessTest.java b/src/test/java/com/google/devtools/build/lib/sandbox/FakeSandboxfsProcessTest.java
index 06c6b2b234..994ae2c70e 100644
--- a/src/test/java/com/google/devtools/build/lib/sandbox/FakeSandboxfsProcessTest.java
+++ b/src/test/java/com/google/devtools/build/lib/sandbox/FakeSandboxfsProcessTest.java
@@ -17,6 +17,7 @@ package com.google.devtools.build.lib.sandbox;
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.devtools.build.lib.testutil.MoreAsserts.assertThrows;
 
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
@@ -32,7 +33,7 @@ public class FakeSandboxfsProcessTest extends BaseSandboxfsProcessTest {
 
   @Override
   Path newTmpDir() throws IOException {
-    FileSystem fileSystem = new InMemoryFileSystem();
+    FileSystem fileSystem = new InMemoryFileSystem(DigestHashFunction.MD5);
     Path tmpDir = fileSystem.getPath("/tmp");
     tmpDir.createDirectory();
     return tmpDir;
diff --git a/src/test/java/com/google/devtools/build/lib/sandbox/LinuxSandboxUtilTest.java b/src/test/java/com/google/devtools/build/lib/sandbox/LinuxSandboxUtilTest.java
index 8a2b4b3a75..6ba265103e 100644
--- a/src/test/java/com/google/devtools/build/lib/sandbox/LinuxSandboxUtilTest.java
+++ b/src/test/java/com/google/devtools/build/lib/sandbox/LinuxSandboxUtilTest.java
@@ -20,6 +20,7 @@ import static com.google.devtools.build.lib.testutil.MoreAsserts.assertThrows;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.ImmutableSortedMap;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
@@ -37,7 +38,7 @@ public final class LinuxSandboxUtilTest {
 
   @Before
   public final void createFileSystem() {
-    testFS = new InMemoryFileSystem();
+    testFS = new InMemoryFileSystem(DigestHashFunction.MD5);
   }
 
   @Test
@@ -97,7 +98,7 @@ public final class LinuxSandboxUtilTest {
     boolean useFakeHostname = true;
     boolean useDebugMode = true;
 
-    FileSystem fileSystem = new InMemoryFileSystem();
+    FileSystem fileSystem = new InMemoryFileSystem(DigestHashFunction.MD5);
     Path workDir = fileSystem.getPath("/work");
     Path concreteDir = workDir.getRelative("concrete");
     Path sandboxDir = workDir.getRelative("sandbox");
diff --git a/src/test/java/com/google/devtools/build/lib/sandbox/SandboxTestCase.java b/src/test/java/com/google/devtools/build/lib/sandbox/SandboxTestCase.java
index 8489c7d914..0b26414f95 100644
--- a/src/test/java/com/google/devtools/build/lib/sandbox/SandboxTestCase.java
+++ b/src/test/java/com/google/devtools/build/lib/sandbox/SandboxTestCase.java
@@ -14,6 +14,7 @@
 package com.google.devtools.build.lib.sandbox;
 
 import com.google.devtools.build.lib.testutil.TestUtils;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
@@ -26,7 +27,7 @@ public class SandboxTestCase {
 
   @Before
   public final void createTestRoot() throws Exception {
-    fileSystem = new InMemoryFileSystem();
+    fileSystem = new InMemoryFileSystem(DigestHashFunction.MD5);
     testRoot = fileSystem.getPath(TestUtils.tmpDir());
     testRoot.createDirectoryAndParents();
   }
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/ASTFileLookupFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/ASTFileLookupFunctionTest.java
index 5395b90a8c..123da88426 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/ASTFileLookupFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/ASTFileLookupFunctionTest.java
@@ -23,6 +23,7 @@ import com.google.devtools.build.lib.cmdline.PackageIdentifier;
 import com.google.devtools.build.lib.packages.NoSuchPackageException;
 import com.google.devtools.build.lib.skyframe.util.SkyframeExecutorTestUtils;
 import com.google.devtools.build.lib.syntax.SkylarkImport;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileStatus;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
@@ -44,6 +45,10 @@ public class ASTFileLookupFunctionTest extends BuildViewTestCase {
   private class MockFileSystem extends InMemoryFileSystem {
     boolean statThrowsIoException;
 
+    private MockFileSystem() {
+      super(DigestHashFunction.MD5);
+    }
+
     @Override
     public FileStatus stat(Path path, boolean followSymlinks) throws IOException {
       if (statThrowsIoException
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/ArtifactFunctionTestCase.java b/src/test/java/com/google/devtools/build/lib/skyframe/ArtifactFunctionTestCase.java
index 5a1ca443b1..e8e0e0bcfb 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/ArtifactFunctionTestCase.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/ArtifactFunctionTestCase.java
@@ -31,6 +31,7 @@ import com.google.devtools.build.lib.testutil.TestConstants;
 import com.google.devtools.build.lib.testutil.TestRuleClassProvider;
 import com.google.devtools.build.lib.testutil.TestUtils;
 import com.google.devtools.build.lib.util.io.TimestampGranularityMonitor;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.Root;
@@ -161,6 +162,11 @@ abstract class ArtifactFunctionTestCase {
 
   /** InMemoryFileSystem that can pretend to do a fast digest. */
   protected class CustomInMemoryFs extends InMemoryFileSystem {
+
+    CustomInMemoryFs() {
+      super(DigestHashFunction.MD5);
+    }
+
     @Override
     protected byte[] getFastDigest(Path path) throws IOException {
       return fastDigest ? getDigest(path) : null;
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/DiffAwarenessManagerTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/DiffAwarenessManagerTest.java
index 5dbbaba462..6b5d6250ec 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/DiffAwarenessManagerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/DiffAwarenessManagerTest.java
@@ -21,6 +21,7 @@ import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Maps;
 import com.google.devtools.build.lib.events.util.EventCollectionApparatus;
 import com.google.devtools.build.lib.skyframe.DiffAwarenessManager.ProcessableModifiedFileSet;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.ModifiedFileSet;
 import com.google.devtools.build.lib.vfs.PathFragment;
@@ -46,7 +47,7 @@ public class DiffAwarenessManagerTest {
 
   @Before
   public final void createFileSystem() throws Exception  {
-    fs = new InMemoryFileSystem();
+    fs = new InMemoryFileSystem(DigestHashFunction.MD5);
   }
 
   @Before
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/FileArtifactValueTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/FileArtifactValueTest.java
index 1e85b6c8b3..e437987201 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/FileArtifactValueTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/FileArtifactValueTest.java
@@ -21,6 +21,7 @@ import com.google.common.io.BaseEncoding;
 import com.google.common.testing.EqualsTester;
 import com.google.devtools.build.lib.actions.FileArtifactValue;
 import com.google.devtools.build.lib.testutil.ManualClock;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
@@ -33,7 +34,7 @@ import org.junit.runners.JUnit4;
 @RunWith(JUnit4.class)
 public class FileArtifactValueTest {
   private final ManualClock clock = new ManualClock();
-  private final FileSystem fs = new InMemoryFileSystem(clock);
+  private final FileSystem fs = new InMemoryFileSystem(clock, DigestHashFunction.MD5);
 
   private Path scratchFile(String name, long mtime, String content) throws IOException {
     Path path = fs.getPath(name);
@@ -159,7 +160,7 @@ public class FileArtifactValueTest {
   public void testIOException() throws Exception {
     final IOException exception = new IOException("beep");
     FileSystem fs =
-        new InMemoryFileSystem() {
+        new InMemoryFileSystem(DigestHashFunction.MD5) {
           @Override
           public byte[] getDigest(Path path) throws IOException {
             throw exception;
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/FileFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/FileFunctionTest.java
index b76bbcd24d..4d3a7d5228 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/FileFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/FileFunctionTest.java
@@ -52,6 +52,7 @@ import com.google.devtools.build.lib.testutil.TestRuleClassProvider;
 import com.google.devtools.build.lib.testutil.TestUtils;
 import com.google.devtools.build.lib.util.Pair;
 import com.google.devtools.build.lib.util.io.TimestampGranularityMonitor;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileStatus;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
@@ -1612,7 +1613,7 @@ public class FileFunctionTest {
     private final Map<Path, IOException> stubbedFastDigestErrors = Maps.newHashMap();
 
     public CustomInMemoryFs(ManualClock manualClock) {
-      super(manualClock);
+      super(manualClock, DigestHashFunction.MD5);
     }
 
     public void stubFastDigestError(Path path, IOException error) {
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/FileSymlinkCycleUniquenessFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/FileSymlinkCycleUniquenessFunctionTest.java
index 38bffd74c5..a092445829 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/FileSymlinkCycleUniquenessFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/FileSymlinkCycleUniquenessFunctionTest.java
@@ -15,6 +15,7 @@ package com.google.devtools.build.lib.skyframe;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.testing.EqualsTester;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import com.google.devtools.build.lib.vfs.Root;
 import com.google.devtools.build.lib.vfs.RootedPath;
@@ -28,7 +29,7 @@ public class FileSymlinkCycleUniquenessFunctionTest {
 
   @Test
   public void testHashCodeAndEqualsContract() throws Exception {
-    Root root = Root.fromPath(new InMemoryFileSystem().getPath("/root"));
+    Root root = Root.fromPath(new InMemoryFileSystem(DigestHashFunction.MD5).getPath("/root"));
     RootedPath p1 = RootedPath.toRootedPath(root, PathFragment.create("p1"));
     RootedPath p2 = RootedPath.toRootedPath(root, PathFragment.create("p2"));
     RootedPath p3 = RootedPath.toRootedPath(root, PathFragment.create("p3"));
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java
index 8ae221911e..6ab8e17f37 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java
@@ -48,6 +48,7 @@ import com.google.devtools.build.lib.testutil.TimestampGranularityUtils;
 import com.google.devtools.build.lib.util.io.OutErr;
 import com.google.devtools.build.lib.util.io.TimestampGranularityMonitor;
 import com.google.devtools.build.lib.vfs.BatchStat;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileStatus;
 import com.google.devtools.build.lib.vfs.FileStatusWithDigest;
 import com.google.devtools.build.lib.vfs.FileStatusWithDigestAdapter;
@@ -839,7 +840,7 @@ public class FilesystemValueCheckerTest {
     boolean readlinkThrowsIoException;
 
     MockFileSystem() {
-      super();
+      super(DigestHashFunction.MD5);
     }
 
     @Override
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/GlobFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/GlobFunctionTest.java
index 7d118c6f0c..39ca9f97fb 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/GlobFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/GlobFunctionTest.java
@@ -43,6 +43,7 @@ import com.google.devtools.build.lib.syntax.SkylarkSemantics;
 import com.google.devtools.build.lib.testutil.ManualClock;
 import com.google.devtools.build.lib.testutil.TestConstants;
 import com.google.devtools.build.lib.util.io.TimestampGranularityMonitor;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.Dirent;
 import com.google.devtools.build.lib.vfs.FileStatus;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
@@ -781,7 +782,7 @@ public abstract class GlobFunctionTest {
     private Map<Path, FileStatus> stubbedStats = Maps.newHashMap();
 
     public CustomInMemoryFs(ManualClock manualClock) {
-      super(manualClock);
+      super(manualClock, DigestHashFunction.MD5);
     }
 
     public void stubStat(Path path, @Nullable FileStatus stubbedResult) {
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/PackageFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/PackageFunctionTest.java
index 0dd046d67d..da6a1d4a27 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/PackageFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/PackageFunctionTest.java
@@ -36,6 +36,7 @@ import com.google.devtools.build.lib.pkgcache.PathPackageLocator;
 import com.google.devtools.build.lib.skyframe.util.SkyframeExecutorTestUtils;
 import com.google.devtools.build.lib.testutil.ManualClock;
 import com.google.devtools.build.lib.util.io.TimestampGranularityMonitor;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.Dirent;
 import com.google.devtools.build.lib.vfs.FileStatus;
 import com.google.devtools.build.lib.vfs.FileSystem;
@@ -760,7 +761,7 @@ public class PackageFunctionTest extends BuildViewTestCase {
     private final Map<Path, IOException> pathsToErrorOnGetInputStream = Maps.newHashMap();
 
     public CustomInMemoryFs(ManualClock manualClock) {
-      super(manualClock);
+      super(manualClock, DigestHashFunction.MD5);
     }
 
     public void stubStat(Path path, @Nullable FileStatus stubbedResult) {
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/ParallelBuilderTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/ParallelBuilderTest.java
index b03a0e9eae..9065ef17ab 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/ParallelBuilderTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/ParallelBuilderTest.java
@@ -41,6 +41,7 @@ import com.google.devtools.build.lib.testutil.BlazeTestUtils;
 import com.google.devtools.build.lib.testutil.Suite;
 import com.google.devtools.build.lib.testutil.TestSpec;
 import com.google.devtools.build.lib.testutil.TestUtils;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileStatus;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
@@ -238,58 +239,59 @@ public class ParallelBuilderTest extends TimestampBuilderTestCase {
 
   @Test
   public void testUpdateCacheError() throws Exception {
-    FileSystem fs = new InMemoryFileSystem() {
-      @Override
-      public FileStatus stat(Path path, boolean followSymlinks) throws IOException {
-        final FileStatus stat = super.stat(path, followSymlinks);
-        if (path.toString().endsWith("/out/foo")) {
-          return new FileStatus() {
-            private final FileStatus original = stat;
+    FileSystem fs =
+        new InMemoryFileSystem(DigestHashFunction.MD5) {
+          @Override
+          public FileStatus stat(Path path, boolean followSymlinks) throws IOException {
+            final FileStatus stat = super.stat(path, followSymlinks);
+            if (path.toString().endsWith("/out/foo")) {
+              return new FileStatus() {
+                private final FileStatus original = stat;
 
-            @Override
-            public boolean isSymbolicLink() {
-              return original.isSymbolicLink();
-            }
+                @Override
+                public boolean isSymbolicLink() {
+                  return original.isSymbolicLink();
+                }
 
-            @Override
-            public boolean isFile() {
-              return original.isFile();
-            }
+                @Override
+                public boolean isFile() {
+                  return original.isFile();
+                }
 
-            @Override
-            public boolean isDirectory() {
-              return original.isDirectory();
-            }
+                @Override
+                public boolean isDirectory() {
+                  return original.isDirectory();
+                }
 
-            @Override
-            public boolean isSpecialFile() {
-              return original.isSpecialFile();
-            }
+                @Override
+                public boolean isSpecialFile() {
+                  return original.isSpecialFile();
+                }
 
-            @Override
-            public long getSize() throws IOException {
-              return original.getSize();
-            }
+                @Override
+                public long getSize() throws IOException {
+                  return original.getSize();
+                }
 
-            @Override
-            public long getNodeId() throws IOException {
-              return original.getNodeId();
-            }
+                @Override
+                public long getNodeId() throws IOException {
+                  return original.getNodeId();
+                }
 
-            @Override
-            public long getLastModifiedTime() throws IOException {
-              throw new IOException();
-            }
+                @Override
+                public long getLastModifiedTime() throws IOException {
+                  throw new IOException();
+                }
 
-            @Override
-            public long getLastChangeTime() throws IOException {
-              throw new IOException();
+                @Override
+                public long getLastChangeTime() throws IOException {
+                  throw new IOException();
+                }
+              };
             }
-          };
-        }
-        return stat;
-      }
-    };
+            return stat;
+          }
+        };
     Artifact foo = createDerivedArtifact(fs, "foo");
     registerAction(new TestAction(TestAction.NO_EFFECT, emptySet, ImmutableList.of(foo)));
     reporter.removeHandler(failFastHandler);
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/SkyframeLabelVisitorTestCase.java b/src/test/java/com/google/devtools/build/lib/skyframe/SkyframeLabelVisitorTestCase.java
index fae9d22012..1a380f5f4b 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/SkyframeLabelVisitorTestCase.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/SkyframeLabelVisitorTestCase.java
@@ -35,6 +35,7 @@ import com.google.devtools.build.lib.packages.Target;
 import com.google.devtools.build.lib.packages.util.PackageLoadingTestCase;
 import com.google.devtools.build.lib.pkgcache.TransitivePackageLoader;
 import com.google.devtools.build.lib.testutil.ManualClock;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileStatus;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.ModifiedFileSet;
@@ -246,7 +247,7 @@ abstract public class SkyframeLabelVisitorTestCase extends PackageLoadingTestCas
     private Map<Path, FileStatus> stubbedStats = Maps.newHashMap();
 
     public CustomInMemoryFs(ManualClock manualClock) {
-      super(manualClock);
+      super(manualClock, DigestHashFunction.MD5);
     }
 
     public void stubStat(Path path, @Nullable FileStatus stubbedResult) {
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/TargetMarkerFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/TargetMarkerFunctionTest.java
index 6778dc8862..fb43ad26e1 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/TargetMarkerFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/TargetMarkerFunctionTest.java
@@ -25,6 +25,7 @@ import com.google.devtools.build.lib.cmdline.PackageIdentifier;
 import com.google.devtools.build.lib.packages.BuildFileNotFoundException;
 import com.google.devtools.build.lib.packages.NoSuchTargetException;
 import com.google.devtools.build.lib.skyframe.util.SkyframeExecutorTestUtils;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileStatus;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.ModifiedFileSet;
@@ -145,7 +146,7 @@ public class TargetMarkerFunctionTest extends BuildViewTestCase {
     private Map<Path, IOException> stubbedStatExceptions = Maps.newHashMap();
 
     public CustomInMemoryFs() {
-      super(BlazeClock.instance());
+      super(BlazeClock.instance(), DigestHashFunction.MD5);
     }
 
     public void stubStatIOException(Path path, IOException stubbedResult) {
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/packages/AbstractPackageLoaderTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/packages/AbstractPackageLoaderTest.java
index d83b570366..1da13d530b 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/packages/AbstractPackageLoaderTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/packages/AbstractPackageLoaderTest.java
@@ -27,6 +27,7 @@ import com.google.devtools.build.lib.events.Reporter;
 import com.google.devtools.build.lib.events.StoredEventHandler;
 import com.google.devtools.build.lib.packages.NoSuchPackageException;
 import com.google.devtools.build.lib.packages.Package;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
@@ -44,7 +45,7 @@ public abstract class AbstractPackageLoaderTest {
 
   @Before
   public final void init() throws Exception {
-    fs = new InMemoryFileSystem();
+    fs = new InMemoryFileSystem(DigestHashFunction.MD5);
     workspaceDir = fs.getPath("/workspace/");
     workspaceDir.createDirectoryAndParents();
     reporter = new Reporter(new EventBus());
diff --git a/src/test/java/com/google/devtools/build/lib/testutil/FoundationTestCase.java b/src/test/java/com/google/devtools/build/lib/testutil/FoundationTestCase.java
index f93d93612b..0641e65b10 100644
--- a/src/test/java/com/google/devtools/build/lib/testutil/FoundationTestCase.java
+++ b/src/test/java/com/google/devtools/build/lib/testutil/FoundationTestCase.java
@@ -22,6 +22,7 @@ import com.google.devtools.build.lib.events.EventCollector;
 import com.google.devtools.build.lib.events.EventHandler;
 import com.google.devtools.build.lib.events.EventKind;
 import com.google.devtools.build.lib.events.Reporter;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
@@ -95,7 +96,7 @@ public abstract class FoundationTestCase {
    * Creates the file system; override to inject FS behavior.
    */
   protected FileSystem createFileSystem() {
-    return new InMemoryFileSystem(BlazeClock.instance());
+    return new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5);
   }
 
   // Mix-in assertions:
diff --git a/src/test/java/com/google/devtools/build/lib/testutil/Scratch.java b/src/test/java/com/google/devtools/build/lib/testutil/Scratch.java
index e5bf9ea8e9..34538f78dd 100644
--- a/src/test/java/com/google/devtools/build/lib/testutil/Scratch.java
+++ b/src/test/java/com/google/devtools/build/lib/testutil/Scratch.java
@@ -16,6 +16,7 @@ package com.google.devtools.build.lib.testutil;
 
 import com.google.common.io.ByteStreams;
 import com.google.devtools.build.lib.clock.BlazeClock;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
@@ -41,14 +42,14 @@ public final class Scratch {
    * Create a new ScratchFileSystem using the {@link InMemoryFileSystem}
    */
   public Scratch() {
-    this(new InMemoryFileSystem(BlazeClock.instance()), "/");
+    this(new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5), "/");
   }
 
   /**
    * Create a new ScratchFileSystem using the {@link InMemoryFileSystem}
    */
   public Scratch(String workingDir) {
-    this(new InMemoryFileSystem(BlazeClock.instance()), workingDir);
+    this(new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5), workingDir);
   }
 
   /**
diff --git a/src/test/java/com/google/devtools/build/lib/testutil/TestFileOutErr.java b/src/test/java/com/google/devtools/build/lib/testutil/TestFileOutErr.java
index fb912c5320..1aec571db5 100644
--- a/src/test/java/com/google/devtools/build/lib/testutil/TestFileOutErr.java
+++ b/src/test/java/com/google/devtools/build/lib/testutil/TestFileOutErr.java
@@ -14,6 +14,7 @@
 package com.google.devtools.build.lib.testutil;
 
 import com.google.devtools.build.lib.util.io.FileOutErr;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
@@ -38,7 +39,7 @@ public class TestFileOutErr extends FileOutErr {
   }
 
   private static Path newInMemoryFile(File root, String name) {
-    InMemoryFileSystem inMemFS = new InMemoryFileSystem();
+    InMemoryFileSystem inMemFS = new InMemoryFileSystem(DigestHashFunction.MD5);
     Path directory = inMemFS.getPath(root.getPath());
     try {
       FileSystemUtils.createDirectoryAndParents(directory);
diff --git a/src/test/java/com/google/devtools/build/lib/util/FileTypeTest.java b/src/test/java/com/google/devtools/build/lib/util/FileTypeTest.java
index 9662ca5fa6..fa6faf8353 100644
--- a/src/test/java/com/google/devtools/build/lib/util/FileTypeTest.java
+++ b/src/test/java/com/google/devtools/build/lib/util/FileTypeTest.java
@@ -19,6 +19,7 @@ import com.google.common.base.Joiner;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Lists;
 import com.google.devtools.build.lib.util.FileType.HasFileType;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
@@ -83,7 +84,7 @@ public class FileTypeTest {
 
   @Test
   public void handlesPathObjects() {
-    Path readme = new InMemoryFileSystem().getPath("/readme.txt");
+    Path readme = new InMemoryFileSystem(DigestHashFunction.MD5).getPath("/readme.txt");
     assertThat(TEXT.matches(readme)).isTrue();
   }
 
diff --git a/src/test/java/com/google/devtools/build/lib/util/FingerprintTest.java b/src/test/java/com/google/devtools/build/lib/util/FingerprintTest.java
index 372b48d80c..c5dd670344 100644
--- a/src/test/java/com/google/devtools/build/lib/util/FingerprintTest.java
+++ b/src/test/java/com/google/devtools/build/lib/util/FingerprintTest.java
@@ -18,6 +18,7 @@ import static java.nio.charset.StandardCharsets.UTF_8;
 
 import com.google.common.collect.ImmutableList;
 import com.google.devtools.build.lib.clock.BlazeClock;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
@@ -116,7 +117,7 @@ public class FingerprintTest {
     PathFragment pf = PathFragment.create("/etc/pwd");
     assertThat(new Fingerprint().addPath(pf).hexDigestAndReset())
         .isEqualTo("63ab5c47c117635407a1af6377e216bc");
-    Path p = new InMemoryFileSystem(BlazeClock.instance()).getPath(pf);
+    Path p = new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5).getPath(pf);
     assertThat(new Fingerprint().addPath(p).hexDigestAndReset())
         .isEqualTo("63ab5c47c117635407a1af6377e216bc");
   }
diff --git a/src/test/java/com/google/devtools/build/lib/vfs/FileSystemUtilsTest.java b/src/test/java/com/google/devtools/build/lib/vfs/FileSystemUtilsTest.java
index cd6be682a2..b55d47542a 100644
--- a/src/test/java/com/google/devtools/build/lib/vfs/FileSystemUtilsTest.java
+++ b/src/test/java/com/google/devtools/build/lib/vfs/FileSystemUtilsTest.java
@@ -56,7 +56,7 @@ public class FileSystemUtilsTest {
   @Before
   public final void initializeFileSystem() throws Exception  {
     clock = new ManualClock();
-    fileSystem = new InMemoryFileSystem(clock);
+    fileSystem = new InMemoryFileSystem(clock, DigestHashFunction.MD5);
     workingDir = fileSystem.getPath("/workingDir");
     workingDir.createDirectory();
   }
@@ -372,6 +372,11 @@ public class FileSystemUtilsTest {
   @Test
   public void testMoveFileAcrossDevices() throws Exception {
     class MultipleDeviceFS extends InMemoryFileSystem {
+
+      MultipleDeviceFS() {
+        super(DigestHashFunction.MD5);
+      }
+
       @Override
       public void renameTo(Path source, Path target) throws IOException {
         if (!source.startsWith(target.asFragment().subFragment(0, 1))) {
diff --git a/src/test/java/com/google/devtools/build/lib/vfs/GlobTest.java b/src/test/java/com/google/devtools/build/lib/vfs/GlobTest.java
index 5b0958fae1..0a080f4792 100644
--- a/src/test/java/com/google/devtools/build/lib/vfs/GlobTest.java
+++ b/src/test/java/com/google/devtools/build/lib/vfs/GlobTest.java
@@ -54,15 +54,16 @@ public class GlobTest {
 
   @Before
   public final void initializeFileSystem() throws Exception  {
-    fs = new InMemoryFileSystem() {
-      @Override
-      public Collection<Dirent> readdir(Path path, boolean followSymlinks) throws IOException {
-        if (path.equals(throwOnReaddir)) {
-          throw new FileNotFoundException(path.getPathString());
-        }
-        return super.readdir(path, followSymlinks);
-      }
-    };
+    fs =
+        new InMemoryFileSystem(DigestHashFunction.MD5) {
+          @Override
+          public Collection<Dirent> readdir(Path path, boolean followSymlinks) throws IOException {
+            if (path.equals(throwOnReaddir)) {
+              throw new FileNotFoundException(path.getPathString());
+            }
+            return super.readdir(path, followSymlinks);
+          }
+        };
     tmpPath = fs.getPath("/globtmp");
     for (String dir : ImmutableList.of("foo/bar/wiz",
                          "foo/barnacle/wiz",
diff --git a/src/test/java/com/google/devtools/build/lib/vfs/JavaIoFileSystemTest.java b/src/test/java/com/google/devtools/build/lib/vfs/JavaIoFileSystemTest.java
index 056b5f0f1a..ccafd494a9 100644
--- a/src/test/java/com/google/devtools/build/lib/vfs/JavaIoFileSystemTest.java
+++ b/src/test/java/com/google/devtools/build/lib/vfs/JavaIoFileSystemTest.java
@@ -50,7 +50,7 @@ public class JavaIoFileSystemTest extends SymlinkAwareFileSystemTest {
   @Override
   public FileSystem getFreshFileSystem() {
     clock = new ManualClock();
-    return new JavaIoFileSystem(clock);
+    return new JavaIoFileSystem(clock, DigestHashFunction.MD5);
   }
 
   // Tests are inherited from the FileSystemTest
diff --git a/src/test/java/com/google/devtools/build/lib/vfs/PathAbstractTest.java b/src/test/java/com/google/devtools/build/lib/vfs/PathAbstractTest.java
index 7494683391..4fa70628bd 100644
--- a/src/test/java/com/google/devtools/build/lib/vfs/PathAbstractTest.java
+++ b/src/test/java/com/google/devtools/build/lib/vfs/PathAbstractTest.java
@@ -37,7 +37,7 @@ public abstract class PathAbstractTest {
 
   @Before
   public void setup() {
-    fileSystem = new InMemoryFileSystem(BlazeClock.instance());
+    fileSystem = new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5);
     isCaseSensitive = OsPathPolicy.getFilePathOs().isCaseSensitive();
   }
 
diff --git a/src/test/java/com/google/devtools/build/lib/vfs/PathFragmentTest.java b/src/test/java/com/google/devtools/build/lib/vfs/PathFragmentTest.java
index 78986e0f5e..20deec04c3 100644
--- a/src/test/java/com/google/devtools/build/lib/vfs/PathFragmentTest.java
+++ b/src/test/java/com/google/devtools/build/lib/vfs/PathFragmentTest.java
@@ -40,7 +40,7 @@ public class PathFragmentTest {
 
   @Test
   public void testEqualsAndHashCode() {
-    InMemoryFileSystem filesystem = new InMemoryFileSystem();
+    InMemoryFileSystem filesystem = new InMemoryFileSystem(DigestHashFunction.MD5);
 
     new EqualsTester()
         .addEqualityGroup(
diff --git a/src/test/java/com/google/devtools/build/lib/vfs/RecursiveGlobTest.java b/src/test/java/com/google/devtools/build/lib/vfs/RecursiveGlobTest.java
index 51b3e79529..d57f23f1b0 100644
--- a/src/test/java/com/google/devtools/build/lib/vfs/RecursiveGlobTest.java
+++ b/src/test/java/com/google/devtools/build/lib/vfs/RecursiveGlobTest.java
@@ -37,7 +37,7 @@ public class RecursiveGlobTest {
 
   @Before
   public final void initializeFileSystem() throws Exception  {
-    fileSystem = new InMemoryFileSystem(BlazeClock.instance());
+    fileSystem = new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5);
     tmpPath = fileSystem.getPath("/rglobtmp");
     for (String dir : ImmutableList.of("foo/bar/wiz",
                          "foo/baz/wiz",
diff --git a/src/test/java/com/google/devtools/build/lib/vfs/RootTest.java b/src/test/java/com/google/devtools/build/lib/vfs/RootTest.java
index 640f8c4c91..5d15bf9ed2 100644
--- a/src/test/java/com/google/devtools/build/lib/vfs/RootTest.java
+++ b/src/test/java/com/google/devtools/build/lib/vfs/RootTest.java
@@ -35,12 +35,12 @@ public class RootTest {
 
   @Before
   public final void initializeFileSystem() throws Exception {
-    fs = new InMemoryFileSystem(BlazeClock.instance());
+    fs = new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5);
   }
 
   @Test
   public void testEqualsAndHashCodeContract() throws Exception {
-    FileSystem otherFs = new InMemoryFileSystem(BlazeClock.instance());
+    FileSystem otherFs = new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5);
     new EqualsTester()
         .addEqualityGroup(Root.absoluteRoot(fs), Root.absoluteRoot(fs))
         .addEqualityGroup(Root.absoluteRoot(otherFs), Root.absoluteRoot(otherFs))
@@ -68,7 +68,7 @@ public class RootTest {
 
   @Test
   public void testFilesystemTransform() throws Exception {
-    FileSystem fs2 = new InMemoryFileSystem(BlazeClock.instance());
+    FileSystem fs2 = new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5);
     Root root = Root.fromPath(fs.getPath("/foo"));
     Root root2 = Root.toFileSystem(root, fs2);
     assertThat(root2.asPath().getFileSystem()).isSameAs(fs2);
diff --git a/src/test/java/com/google/devtools/build/lib/vfs/RootedPathTest.java b/src/test/java/com/google/devtools/build/lib/vfs/RootedPathTest.java
index 6f452c2fcb..aa1513f734 100644
--- a/src/test/java/com/google/devtools/build/lib/vfs/RootedPathTest.java
+++ b/src/test/java/com/google/devtools/build/lib/vfs/RootedPathTest.java
@@ -31,7 +31,7 @@ public class RootedPathTest {
 
   @Before
   public final void initializeFileSystem() throws Exception  {
-    filesystem = new InMemoryFileSystem(BlazeClock.instance());
+    filesystem = new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5);
     root = filesystem.getPath("/");
   }
 
diff --git a/src/test/java/com/google/devtools/build/lib/vfs/SearchPathTest.java b/src/test/java/com/google/devtools/build/lib/vfs/SearchPathTest.java
index e815a8cc23..01069d1e8e 100644
--- a/src/test/java/com/google/devtools/build/lib/vfs/SearchPathTest.java
+++ b/src/test/java/com/google/devtools/build/lib/vfs/SearchPathTest.java
@@ -25,7 +25,7 @@ import org.junit.runners.JUnit4;
 
 @RunWith(JUnit4.class)
 public class SearchPathTest {
-  private FileSystem fs = new InMemoryFileSystem();
+  private FileSystem fs = new InMemoryFileSystem(DigestHashFunction.MD5);
 
   @Test
   public void testNull() throws Exception {
diff --git a/src/test/java/com/google/devtools/build/lib/vfs/inmemoryfs/InMemoryFileSystemTest.java b/src/test/java/com/google/devtools/build/lib/vfs/inmemoryfs/InMemoryFileSystemTest.java
index 6f2b4e7858..8c1ffac7c2 100644
--- a/src/test/java/com/google/devtools/build/lib/vfs/inmemoryfs/InMemoryFileSystemTest.java
+++ b/src/test/java/com/google/devtools/build/lib/vfs/inmemoryfs/InMemoryFileSystemTest.java
@@ -19,6 +19,7 @@ import static org.junit.Assert.fail;
 import com.google.common.collect.Lists;
 import com.google.devtools.build.lib.clock.BlazeClock;
 import com.google.devtools.build.lib.testutil.TestThread;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
@@ -44,7 +45,7 @@ public class InMemoryFileSystemTest extends SymlinkAwareFileSystemTest {
 
   @Override
   public FileSystem getFreshFileSystem() {
-    return new InMemoryFileSystem(BlazeClock.instance());
+    return new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5);
   }
 
   @Override
diff --git a/src/test/java/com/google/devtools/build/lib/vfs/util/FsApparatus.java b/src/test/java/com/google/devtools/build/lib/vfs/util/FsApparatus.java
index 1f78b189bf..1305c992b6 100644
--- a/src/test/java/com/google/devtools/build/lib/vfs/util/FsApparatus.java
+++ b/src/test/java/com/google/devtools/build/lib/vfs/util/FsApparatus.java
@@ -16,6 +16,7 @@ package com.google.devtools.build.lib.vfs.util;
 import com.google.devtools.build.lib.clock.BlazeClock;
 import com.google.devtools.build.lib.testutil.TestUtils;
 import com.google.devtools.build.lib.util.StringUtilities;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
@@ -68,7 +69,7 @@ public class FsApparatus {
   }
 
   private FsApparatus() {
-    fileSystem = new InMemoryFileSystem(BlazeClock.instance());
+    fileSystem = new InMemoryFileSystem(BlazeClock.instance(), DigestHashFunction.MD5);
     workingDir = fileSystem.getPath("/");
   }
 
diff --git a/src/test/java/com/google/devtools/build/lib/worker/ErrorMessageTest.java b/src/test/java/com/google/devtools/build/lib/worker/ErrorMessageTest.java
index 4607b22e74..98de2b8186 100644
--- a/src/test/java/com/google/devtools/build/lib/worker/ErrorMessageTest.java
+++ b/src/test/java/com/google/devtools/build/lib/worker/ErrorMessageTest.java
@@ -18,6 +18,7 @@ import static com.google.common.truth.Truth.assertThat;
 import static java.nio.charset.StandardCharsets.UTF_8;
 
 import com.google.devtools.build.lib.util.OS;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
@@ -85,7 +86,7 @@ public class ErrorMessageTest {
 
   @Test
   public void testErrorMessageWithLogFile() throws Exception {
-    InMemoryFileSystem fs = new InMemoryFileSystem();
+    InMemoryFileSystem fs = new InMemoryFileSystem(DigestHashFunction.MD5);
     Path logFile = fs.getPath("/log.txt");
     FileSystemUtils.writeContent(logFile, UTF_8, logText);
     ErrorMessage errorMessage =
@@ -104,7 +105,7 @@ public class ErrorMessageTest {
       // TODO(#3536): This test is failing on Windows, probably due to line breaks. Fix it!
       return;
     }
-    InMemoryFileSystem fs = new InMemoryFileSystem();
+    InMemoryFileSystem fs = new InMemoryFileSystem(DigestHashFunction.MD5);
     // This file does not exist.
     Path logFile = fs.getPath("/nope.txt");
     ErrorMessage errorMessage =
diff --git a/src/test/java/com/google/devtools/build/lib/worker/WorkerExecRootTest.java b/src/test/java/com/google/devtools/build/lib/worker/WorkerExecRootTest.java
index b7758e66a5..2eb8981feb 100644
--- a/src/test/java/com/google/devtools/build/lib/worker/WorkerExecRootTest.java
+++ b/src/test/java/com/google/devtools/build/lib/worker/WorkerExecRootTest.java
@@ -18,6 +18,7 @@ import static com.google.common.truth.Truth.assertThat;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.testutil.TestUtils;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
@@ -41,7 +42,7 @@ public class WorkerExecRootTest {
 
   @Before
   public final void setupTestDirs() throws IOException {
-    fileSystem = new InMemoryFileSystem();
+    fileSystem = new InMemoryFileSystem(DigestHashFunction.MD5);
     testRoot = fileSystem.getPath(TestUtils.tmpDir());
     testRoot.createDirectoryAndParents();
 
diff --git a/src/test/java/com/google/devtools/build/lib/worker/WorkerFactoryTest.java b/src/test/java/com/google/devtools/build/lib/worker/WorkerFactoryTest.java
index 0552cb8c5a..36f569f138 100644
--- a/src/test/java/com/google/devtools/build/lib/worker/WorkerFactoryTest.java
+++ b/src/test/java/com/google/devtools/build/lib/worker/WorkerFactoryTest.java
@@ -19,6 +19,7 @@ import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSortedMap;
 import com.google.common.hash.HashCode;
+import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
@@ -30,7 +31,7 @@ import org.junit.runners.JUnit4;
 @RunWith(JUnit4.class)
 public class WorkerFactoryTest {
 
-  final FileSystem fs = new InMemoryFileSystem();
+  final FileSystem fs = new InMemoryFileSystem(DigestHashFunction.MD5);
 
   /**
    * Regression test for b/64689608: The execroot of the sandboxed worker process must end with the