Add 10 second timeout waiting for connection before client behaves as-if offline. (#872)

[Port of https://github.com/firebase/firebase-js-sdk/commit/0fa319e5e019dd0d40ab441d2ff9f8f6d4724e43]

* Refactored FSTOnlineState tracking out of FSTRemoteStore and into new
  FSTOnlineStateTracker component.
* Added a 10 second timeout to transition from OnlineState.Unknown to
  OnlineState.Offline rather than waiting indefinitely for the stream to
  succeed or fail.
* Removed hack to run SpecTests using an FSTDispatchQueue that wrapped
  dispatch_get_main_queue(). This was incompatible with [FSTDispatchQueue
  runDelayedCallbacksUntil:] since it queues work and blocks waiting for
  it to complete. Now spec tests create / use a proper FSTDispatchQueue.
* Added a SpecTest to verify OnlineState timeout behavior.
* Misc cleanup:
    * Renamed FSTOnlineState states: Failed => Offline, Healthy => Online
    * Renamed FSTTimerIds (ListenStreamConnection => ListenStreamConnectionBackoff)
    * Added ability to run timers from spec tests.

8 files changed, 264 insertions, 48 deletions

diff --git a/Firestore/Example/Tests/Core/FSTEventManagerTests.mm b/Firestore/Example/Tests/Core/FSTEventManagerTests.mm
index fcde17d..f5f7b5b 100644
--- a/Firestore/Example/Tests/Core/FSTEventManagerTests.mm
+++ b/Firestore/Example/Tests/Core/FSTEventManagerTests.mm
@@ -143,9 +143,9 @@ NS_ASSUME_NONNULL_BEGIN
       .andDo(^(NSInvocation *invocation) {
         [events addObject:@(FSTOnlineStateUnknown)];
       });
-  OCMStub([fakeListener applyChangedOnlineState:FSTOnlineStateHealthy])
+  OCMStub([fakeListener applyChangedOnlineState:FSTOnlineStateOnline])
       .andDo(^(NSInvocation *invocation) {
-        [events addObject:@(FSTOnlineStateHealthy)];
+        [events addObject:@(FSTOnlineStateOnline)];
       });
 
   FSTSyncEngine *syncEngineMock = OCMClassMock([FSTSyncEngine class]);
@@ -154,8 +154,8 @@ NS_ASSUME_NONNULL_BEGIN
 
   [eventManager addListener:fakeListener];
   XCTAssertEqualObjects(events, @[ @(FSTOnlineStateUnknown) ]);
-  [eventManager applyChangedOnlineState:FSTOnlineStateHealthy];
-  XCTAssertEqualObjects(events, (@[ @(FSTOnlineStateUnknown), @(FSTOnlineStateHealthy) ]));
+  [eventManager applyChangedOnlineState:FSTOnlineStateOnline];
+  XCTAssertEqualObjects(events, (@[ @(FSTOnlineStateUnknown), @(FSTOnlineStateOnline) ]));
 }
 
 @end
diff --git a/Firestore/Example/Tests/Core/FSTQueryListenerTests.mm b/Firestore/Example/Tests/Core/FSTQueryListenerTests.mm
index 4856b5f..1b26360 100644
--- a/Firestore/Example/Tests/Core/FSTQueryListenerTests.mm
+++ b/Firestore/Example/Tests/Core/FSTQueryListenerTests.mm
@@ -340,10 +340,10 @@ NS_ASSUME_NONNULL_BEGIN
                           [FSTTargetChange changeWithDocuments:@[ doc1, doc2 ]
                                            currentStatusUpdate:FSTCurrentStatusUpdateMarkCurrent]);
 
-  [listener applyChangedOnlineState:FSTOnlineStateHealthy];  // no event
+  [listener applyChangedOnlineState:FSTOnlineStateOnline];  // no event
   [listener queryDidChangeViewSnapshot:snap1];
   [listener applyChangedOnlineState:FSTOnlineStateUnknown];
-  [listener applyChangedOnlineState:FSTOnlineStateHealthy];
+  [listener applyChangedOnlineState:FSTOnlineStateOnline];
   [listener queryDidChangeViewSnapshot:snap2];
   [listener queryDidChangeViewSnapshot:snap3];
 
@@ -379,11 +379,11 @@ NS_ASSUME_NONNULL_BEGIN
   FSTViewSnapshot *snap1 = FSTTestApplyChanges(view, @[ doc1 ], nil);
   FSTViewSnapshot *snap2 = FSTTestApplyChanges(view, @[ doc2 ], nil);
 
-  [listener applyChangedOnlineState:FSTOnlineStateHealthy];  // no event
+  [listener applyChangedOnlineState:FSTOnlineStateOnline];   // no event
   [listener queryDidChangeViewSnapshot:snap1];               // no event
-  [listener applyChangedOnlineState:FSTOnlineStateFailed];   // event
+  [listener applyChangedOnlineState:FSTOnlineStateOffline];  // event
   [listener applyChangedOnlineState:FSTOnlineStateUnknown];  // no event
-  [listener applyChangedOnlineState:FSTOnlineStateFailed];   // no event
+  [listener applyChangedOnlineState:FSTOnlineStateOffline];  // no event
   [listener queryDidChangeViewSnapshot:snap2];               // another event
 
   FSTDocumentViewChange *change1 =
@@ -419,9 +419,9 @@ NS_ASSUME_NONNULL_BEGIN
   FSTView *view = [[FSTView alloc] initWithQuery:query remoteDocuments:[FSTDocumentKeySet keySet]];
   FSTViewSnapshot *snap1 = FSTTestApplyChanges(view, @[], nil);
 
-  [listener applyChangedOnlineState:FSTOnlineStateHealthy];  // no event
+  [listener applyChangedOnlineState:FSTOnlineStateOnline];   // no event
   [listener queryDidChangeViewSnapshot:snap1];               // no event
-  [listener applyChangedOnlineState:FSTOnlineStateFailed];   // event
+  [listener applyChangedOnlineState:FSTOnlineStateOffline];  // event
 
   FSTViewSnapshot *expectedSnap = [[FSTViewSnapshot alloc]
          initWithQuery:query
@@ -445,8 +445,8 @@ NS_ASSUME_NONNULL_BEGIN
   FSTView *view = [[FSTView alloc] initWithQuery:query remoteDocuments:[FSTDocumentKeySet keySet]];
   FSTViewSnapshot *snap1 = FSTTestApplyChanges(view, @[], nil);
 
-  [listener applyChangedOnlineState:FSTOnlineStateFailed];  // no event
-  [listener queryDidChangeViewSnapshot:snap1];              // event
+  [listener applyChangedOnlineState:FSTOnlineStateOffline];  // no event
+  [listener queryDidChangeViewSnapshot:snap1];               // event
 
   FSTViewSnapshot *expectedSnap = [[FSTViewSnapshot alloc]
          initWithQuery:query
diff --git a/Firestore/Example/Tests/Integration/FSTDatastoreTests.mm b/Firestore/Example/Tests/Integration/FSTDatastoreTests.mm
index 4323ccd..77581d4 100644
--- a/Firestore/Example/Tests/Integration/FSTDatastoreTests.mm
+++ b/Firestore/Example/Tests/Integration/FSTDatastoreTests.mm
@@ -175,7 +175,9 @@ NS_ASSUME_NONNULL_BEGIN
                                workerDispatchQueue:_testWorkerQueue
                                        credentials:&_credentials];
 
-  _remoteStore = [FSTRemoteStore remoteStoreWithLocalStore:_localStore datastore:_datastore];
+  _remoteStore = [[FSTRemoteStore alloc] initWithLocalStore:_localStore
+                                                  datastore:_datastore
+                                        workerDispatchQueue:_testWorkerQueue];
 
   [_testWorkerQueue dispatchAsync:^() {
     [_remoteStore start];
diff --git a/Firestore/Example/Tests/SpecTests/FSTSpecTests.mm b/Firestore/Example/Tests/SpecTests/FSTSpecTests.mm
index 43b2a5f..b00ea07 100644
--- a/Firestore/Example/Tests/SpecTests/FSTSpecTests.mm
+++ b/Firestore/Example/Tests/SpecTests/FSTSpecTests.mm
@@ -22,7 +22,6 @@
 #import "Firestore/Source/Core/FSTEventManager.h"
 #import "Firestore/Source/Core/FSTQuery.h"
 #import "Firestore/Source/Core/FSTSnapshotVersion.h"
-#import "Firestore/Source/Core/FSTViewSnapshot.h"
 #import "Firestore/Source/Local/FSTEagerGarbageCollector.h"
 #import "Firestore/Source/Local/FSTNoOpGarbageCollector.h"
 #import "Firestore/Source/Local/FSTPersistence.h"
@@ -36,6 +35,7 @@
 #import "Firestore/Source/Remote/FSTWatchChange.h"
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTClasses.h"
+#import "Firestore/Source/Util/FSTDispatchQueue.h"
 #import "Firestore/Source/Util/FSTLogger.h"
 
 #import "Firestore/Example/Tests/Remote/FSTWatchChange+Testing.h"
@@ -323,6 +323,27 @@ static NSString *const kNoIOSTag = @"no-ios";
   }
 }
 
+- (void)doRunTimer:(NSString *)timer {
+  FSTTimerID timerID;
+  if ([timer isEqualToString:@"all"]) {
+    timerID = FSTTimerIDAll;
+  } else if ([timer isEqualToString:@"listen_stream_idle"]) {
+    timerID = FSTTimerIDListenStreamIdle;
+  } else if ([timer isEqualToString:@"listen_stream_connection"]) {
+    timerID = FSTTimerIDListenStreamConnectionBackoff;
+  } else if ([timer isEqualToString:@"write_stream_idle"]) {
+    timerID = FSTTimerIDWriteStreamIdle;
+  } else if ([timer isEqualToString:@"write_stream_connection"]) {
+    timerID = FSTTimerIDWriteStreamConnectionBackoff;
+  } else if ([timer isEqualToString:@"online_state_timeout"]) {
+    timerID = FSTTimerIDOnlineStateTimeout;
+  } else {
+    FSTFail(@"runTimer spec step specified unknown timer: %@", timer);
+  }
+
+  [self.driver runTimer:timerID];
+}
+
 - (void)doDisableNetwork {
   [self.driver disableNetwork];
 }
@@ -391,6 +412,8 @@ static NSString *const kNoIOSTag = @"no-ios";
     [self doWriteAck:step[@"writeAck"]];
   } else if (step[@"failWrite"]) {
     [self doFailWrite:step[@"failWrite"]];
+  } else if (step[@"runTimer"]) {
+    [self doRunTimer:step[@"runTimer"]];
   } else if (step[@"enableNetwork"]) {
     if ([step[@"enableNetwork"] boolValue]) {
       [self doEnableNetwork];
diff --git a/Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.h b/Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.h
index 466a347..f3d9a5d 100644
--- a/Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.h
+++ b/Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.h
@@ -20,6 +20,7 @@
 
 #import "Firestore/Source/Core/FSTTypes.h"
 #import "Firestore/Source/Remote/FSTRemoteStore.h"
+#import "Firestore/Source/Util/FSTDispatchQueue.h"
 
 #include "Firestore/core/src/firebase/firestore/auth/user.h"
 
@@ -224,6 +225,11 @@ typedef std::unordered_map<firebase::firestore::auth::User,
 - (void)enableNetwork;
 
 /**
+ * Runs a pending timer callback on the FSTDispatchQueue.
+ */
+- (void)runTimer:(FSTTimerID)timerID;
+
+/**
  * Switches the FSTSyncEngine to a new user. The test driver tracks the outstanding mutations for
  * each user, so future receiveWriteAck/Error operations will validate the write sent to the mock
  * datastore matches the next outstanding write for that user.
diff --git a/Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.mm b/Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.mm
index 07dc84f..bfcd4dd 100644
--- a/Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.mm
+++ b/Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.mm
@@ -31,7 +31,6 @@
 #import "Firestore/Source/Remote/FSTDatastore.h"
 #import "Firestore/Source/Remote/FSTWatchChange.h"
 #import "Firestore/Source/Util/FSTAssert.h"
-#import "Firestore/Source/Util/FSTDispatchQueue.h"
 #import "Firestore/Source/Util/FSTLogger.h"
 
 #import "Firestore/Example/Tests/Core/FSTSyncEngine+Testing.h"
@@ -72,6 +71,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property(nonatomic, strong, readonly) FSTRemoteStore *remoteStore;
 @property(nonatomic, strong, readonly) FSTLocalStore *localStore;
 @property(nonatomic, strong, readonly) FSTSyncEngine *syncEngine;
+@property(nonatomic, strong, readonly) FSTDispatchQueue *dispatchQueue;
 
 #pragma mark - Data structures for holding events sent by the watch stream.
 
@@ -117,16 +117,19 @@ NS_ASSUME_NONNULL_BEGIN
     _databaseInfo = {DatabaseId{"project", "database"}, "persistence", "host", false};
 
     // Set up the sync engine and various stores.
-    dispatch_queue_t mainQueue = dispatch_get_main_queue();
-    FSTDispatchQueue *dispatchQueue = [FSTDispatchQueue queueWith:mainQueue];
+    dispatch_queue_t queue =
+        dispatch_queue_create("sync_engine_test_driver", DISPATCH_QUEUE_SERIAL);
+    _dispatchQueue = [FSTDispatchQueue queueWith:queue];
     _localStore = [[FSTLocalStore alloc] initWithPersistence:persistence
                                             garbageCollector:garbageCollector
                                                  initialUser:initialUser];
     _datastore = [[FSTMockDatastore alloc] initWithDatabaseInfo:&_databaseInfo
-                                            workerDispatchQueue:dispatchQueue
+                                            workerDispatchQueue:_dispatchQueue
                                                     credentials:&_credentialProvider];
 
-    _remoteStore = [FSTRemoteStore remoteStoreWithLocalStore:_localStore datastore:_datastore];
+    _remoteStore = [[FSTRemoteStore alloc] initWithLocalStore:_localStore
+                                                    datastore:_datastore
+                                          workerDispatchQueue:_dispatchQueue];
 
     _syncEngine = [[FSTSyncEngine alloc] initWithLocalStore:_localStore
                                                 remoteStore:_remoteStore
@@ -168,8 +171,10 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 - (void)start {
-  [self.localStore start];
-  [self.remoteStore start];
+  [self.dispatchQueue dispatchSync:^{
+    [self.localStore start];
+    [self.remoteStore start];
+  }];
 }
 
 - (void)validateUsage {
@@ -180,8 +185,10 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 - (void)shutdown {
-  [self.remoteStore shutdown];
-  [self.localStore shutdown];
+  [self.dispatchQueue dispatchSync:^{
+    [self.remoteStore shutdown];
+    [self.localStore shutdown];
+  }];
 }
 
 - (void)validateNextWriteSent:(FSTMutation *)expectedWrite {
@@ -208,19 +215,29 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 - (void)disableNetwork {
-  // Make sure to execute all writes that are currently queued. This allows us
-  // to assert on the total number of requests sent before shutdown.
-  [self.remoteStore fillWritePipeline];
-  [self.remoteStore disableNetwork];
+  [self.dispatchQueue dispatchSync:^{
+    // Make sure to execute all writes that are currently queued. This allows us
+    // to assert on the total number of requests sent before shutdown.
+    [self.remoteStore fillWritePipeline];
+    [self.remoteStore disableNetwork];
+  }];
 }
 
 - (void)enableNetwork {
-  [self.remoteStore enableNetwork];
+  [self.dispatchQueue dispatchSync:^{
+    [self.remoteStore enableNetwork];
+  }];
+}
+
+- (void)runTimer:(FSTTimerID)timerID {
+  [self.dispatchQueue runDelayedCallbacksUntil:timerID];
 }
 
 - (void)changeUser:(const User &)user {
   _currentUser = user;
-  [self.syncEngine userDidChange:user];
+  [self.dispatchQueue dispatchSync:^{
+    [self.syncEngine userDidChange:user];
+  }];
 }
 
 - (FSTOutstandingWrite *)receiveWriteAckWithVersion:(FSTSnapshotVersion *)commitVersion
@@ -230,7 +247,9 @@ NS_ASSUME_NONNULL_BEGIN
   [[self currentOutstandingWrites] removeObjectAtIndex:0];
   [self validateNextWriteSent:write.write];
 
-  [self.datastore ackWriteWithVersion:commitVersion mutationResults:mutationResults];
+  [self.dispatchQueue dispatchSync:^{
+    [self.datastore ackWriteWithVersion:commitVersion mutationResults:mutationResults];
+  }];
 
   return write;
 }
@@ -250,7 +269,9 @@ NS_ASSUME_NONNULL_BEGIN
   }
 
   FSTLog(@"Failing a write.");
-  [self.datastore failWriteWithError:error];
+  [self.dispatchQueue dispatchSync:^{
+    [self.datastore failWriteWithError:error];
+  }];
 
   return write;
 }
@@ -278,13 +299,19 @@ NS_ASSUME_NONNULL_BEGIN
         [self.events addObject:event];
       }];
   self.queryListeners[query] = listener;
-  return [self.eventManager addListener:listener];
+  __block FSTTargetID targetID;
+  [self.dispatchQueue dispatchSync:^{
+    targetID = [self.eventManager addListener:listener];
+  }];
+  return targetID;
 }
 
 - (void)removeUserListenerWithQuery:(FSTQuery *)query {
   FSTQueryListener *listener = self.queryListeners[query];
   [self.queryListeners removeObjectForKey:query];
-  [self.eventManager removeListener:listener];
+  [self.dispatchQueue dispatchSync:^{
+    [self.eventManager removeListener:listener];
+  }];
 }
 
 - (void)writeUserMutation:(FSTMutation *)mutation {
@@ -292,28 +319,34 @@ NS_ASSUME_NONNULL_BEGIN
   write.write = mutation;
   [[self currentOutstandingWrites] addObject:write];
   FSTLog(@"sending a user write.");
-  [self.syncEngine writeMutations:@[ mutation ]
-                       completion:^(NSError *_Nullable error) {
-                         FSTLog(@"A callback was called with error: %@", error);
-                         write.done = YES;
-                         write.error = error;
-                       }];
+  [self.dispatchQueue dispatchSync:^{
+    [self.syncEngine writeMutations:@[ mutation ]
+                         completion:^(NSError *_Nullable error) {
+                           FSTLog(@"A callback was called with error: %@", error);
+                           write.done = YES;
+                           write.error = error;
+                         }];
+  }];
 }
 
 - (void)receiveWatchChange:(FSTWatchChange *)change
            snapshotVersion:(FSTSnapshotVersion *_Nullable)snapshot {
-  [self.datastore writeWatchChange:change snapshotVersion:snapshot];
+  [self.dispatchQueue dispatchSync:^{
+    [self.datastore writeWatchChange:change snapshotVersion:snapshot];
+  }];
 }
 
 - (void)receiveWatchStreamError:(int)errorCode userInfo:(NSDictionary<NSString *, id> *)userInfo {
   NSError *error =
       [NSError errorWithDomain:FIRFirestoreErrorDomain code:errorCode userInfo:userInfo];
 
-  [self.datastore failWatchStreamWithError:error];
-  // Unlike web, stream should re-open synchronously (if we have any listeners)
-  if (self.queryListeners.count > 0) {
-    FSTAssert(self.datastore.isWatchStreamOpen, @"Watch stream is open");
-  }
+  [self.dispatchQueue dispatchSync:^{
+    [self.datastore failWatchStreamWithError:error];
+    // Unlike web, stream should re-open synchronously (if we have any listeners)
+    if (self.queryListeners.count > 0) {
+      FSTAssert(self.datastore.isWatchStreamOpen, @"Watch stream is open");
+    }
+  }];
 }
 
 - (NSDictionary<FSTDocumentKey *, FSTBoxedTargetID *> *)currentLimboDocuments {
diff --git a/Firestore/Example/Tests/SpecTests/json/offline_spec_test.json b/Firestore/Example/Tests/SpecTests/json/offline_spec_test.json
index 6cbbc80..fc9f295 100644
--- a/Firestore/Example/Tests/SpecTests/json/offline_spec_test.json
+++ b/Firestore/Example/Tests/SpecTests/json/offline_spec_test.json
@@ -713,5 +713,157 @@
         }
       }
     ]
+  },
+  "OnlineState timeout triggers offline behavior": {
+    "describeName": "Offline:",
+    "itName": "OnlineState timeout triggers offline behavior",
+    "tags": [],
+    "config": {
+      "useGarbageCollection": true
+    },
+    "steps": [
+      {
+        "userListen": [
+          2,
+          {
+            "path": "collection",
+            "filters": [],
+            "orderBys": []
+          }
+        ],
+        "stateExpect": {
+          "activeTargets": {
+            "2": {
+              "query": {
+                "path": "collection",
+                "filters": [],
+                "orderBys": []
+              },
+              "resumeToken": ""
+            }
+          }
+        }
+      },
+      {
+        "runTimer": "online_state_timeout",
+        "expect": [
+          {
+            "query": {
+              "path": "collection",
+              "filters": [],
+              "orderBys": []
+            },
+            "errorCode": 0,
+            "fromCache": true,
+            "hasPendingWrites": false
+          }
+        ]
+      },
+      {
+        "watchStreamClose": {
+          "error": {
+            "code": 14,
+            "message": "Simulated Backend Error"
+          }
+        }
+      },
+      {
+        "watchStreamClose": {
+          "error": {
+            "code": 14,
+            "message": "Simulated Backend Error"
+          }
+        }
+      },
+      {
+        "watchAck": [
+          2
+        ]
+      },
+      {
+        "watchEntity": {
+          "docs": [
+            [
+              "collection/a",
+              1000,
+              {
+                "key": "a"
+              }
+            ]
+          ],
+          "targets": [
+            2
+          ]
+        }
+      },
+      {
+        "watchCurrent": [
+          [
+            2
+          ],
+          "resume-token-1000"
+        ],
+        "watchSnapshot": 1000,
+        "expect": [
+          {
+            "query": {
+              "path": "collection",
+              "filters": [],
+              "orderBys": []
+            },
+            "added": [
+              [
+                "collection/a",
+                1000,
+                {
+                  "key": "a"
+                }
+              ]
+            ],
+            "errorCode": 0,
+            "fromCache": false,
+            "hasPendingWrites": false
+          }
+        ]
+      },
+      {
+        "runTimer": "all"
+      },
+      {
+        "watchStreamClose": {
+          "error": {
+            "code": 14,
+            "message": "Simulated Backend Error"
+          }
+        },
+        "stateExpect": {
+          "activeTargets": {
+            "2": {
+              "query": {
+                "path": "collection",
+                "filters": [],
+                "orderBys": []
+              },
+              "resumeToken": "resume-token-1000"
+            }
+          }
+        }
+      },
+      {
+        "runTimer": "online_state_timeout",
+        "expect": [
+          {
+            "query": {
+              "path": "collection",
+              "filters": [],
+              "orderBys": []
+            },
+            "errorCode": 0,
+            "fromCache": true,
+            "hasPendingWrites": false
+          }
+        ]
+      }
+    ]
   }
 }
diff --git a/Firestore/Example/Tests/Util/FSTDispatchQueueTests.mm b/Firestore/Example/Tests/Util/FSTDispatchQueueTests.mm
index 9f5b52d..5ef860c 100644
--- a/Firestore/Example/Tests/Util/FSTDispatchQueueTests.mm
+++ b/Firestore/Example/Tests/Util/FSTDispatchQueueTests.mm
@@ -21,9 +21,9 @@
 #import "Firestore/Example/Tests/Util/XCTestCase+Await.h"
 
 // In these generic tests the specific TimerIDs don't matter.
-static const FSTTimerID timerID1 = FSTTimerIDListenStreamConnection;
+static const FSTTimerID timerID1 = FSTTimerIDListenStreamConnectionBackoff;
 static const FSTTimerID timerID2 = FSTTimerIDListenStreamIdle;
-static const FSTTimerID timerID3 = FSTTimerIDWriteStreamConnection;
+static const FSTTimerID timerID3 = FSTTimerIDWriteStreamConnectionBackoff;
 
 @interface FSTDispatchQueueTests : XCTestCase
 @end