Fix Firestore tests for M22 (#834)

* Add FIRFirestoreTests to the Firestore Xcode project

* Avoid waitForExpectations:timeout:

This API was added in Xcode 8.3, but we still build production releases
with Xcode 8.2. waitForExpectationsWithTimeout:handler: is available
from Xcode 7.2.

* Add AppForUnitTesting

Add a utility for constructing a Firebase App for testing.

* Handle the nil UID from FIRAuth

* Avoid running CMake tests twice

* Only build app_testing on Apple platforms

* Revise test.sh messages

1 files changed, 3 insertions, 7 deletions

diff --git a/Firestore/test.sh b/Firestore/test.sh
index b211f46..7be70d0 100755
--- a/Firestore/test.sh
+++ b/Firestore/test.sh
@@ -40,19 +40,15 @@ test_iOS() {
 
 test_CMake() {
   echo "cpu core: $(sysctl -n hw.ncpu)"
-  echo "set cmake build" && \
-    mkdir build && \
+  echo "prepare cmake build" && \
+    mkdir -p build && \
     cd build && \
     cmake .. || \
     exit 1
 
-  echo "initial cmake build" && \
+  echo "cmake build and test" && \
     make -j $(sysctl -n hw.ncpu) all || \
     exit 2
-
-  echo "test Firestore cmake build" && \
-    cd Firestore && \
-    make test
 }
 
 test_iOS; RESULT=$?