FIRApp tests fixes (#7157)

* Core pospec: keep deployment targets in sync

* FIRAppTest: tear down race condition workaround

* style

Author: maksymmalyhin

FirebaseCore.podspec

@@ -17,10 +17,16 @@ Firebase Core includes FIRApp and FIROptions which provide central configuration
   }
 
   s.social_media_url = 'https://twitter.com/Firebase'
-  s.ios.deployment_target = '9.0'
-  s.osx.deployment_target = '10.12'
-  s.tvos.deployment_target = '10.0'
-  s.watchos.deployment_target = '6.0'
+
+  ios_deployment_target = '9.0'
+  osx_deployment_target = '10.12'
+  tvos_deployment_target = '10.0'
+  watchos_deployment_target = '6.0'
+
+  s.ios.deployment_target = ios_deployment_target
+  s.osx.deployment_target = osx_deployment_target
+  s.tvos.deployment_target = tvos_deployment_target
+  s.watchos.deployment_target = watchos_deployment_target
 
   s.cocoapods_version = '>= 1.4.0'
   s.prefix_header_file = false
@@ -50,7 +56,7 @@ Firebase Core includes FIRApp and FIROptions which provide central configuration
     'OTHER_CFLAGS' => '-fno-autolink'
   }
   s.test_spec 'unit' do |unit_tests|
-    unit_tests.platforms = {:ios => '8.0', :osx => '10.11', :tvos => '10.0'}
+    unit_tests.platforms = {:ios => ios_deployment_target, :osx => osx_deployment_target, :tvos => tvos_deployment_target}
     unit_tests.source_files = [
       'FirebaseCore/Tests/Unit/**/*.[mh]',
       'SharedTestUtilities/FIROptionsMock.[mh]',
@@ -61,7 +67,7 @@ Firebase Core includes FIRApp and FIROptions which provide central configuration
   end
 
   s.test_spec 'swift-unit' do |swift_unit_tests|
-    swift_unit_tests.platforms = {:ios => '8.0', :osx => '10.11', :tvos => '10.0'}
+    swift_unit_tests.platforms = {:ios => ios_deployment_target, :osx => osx_deployment_target, :tvos => tvos_deployment_target}
     swift_unit_tests.source_files = [
       'FirebaseCore/Tests/SwiftUnit/**/*.swift',
       'FirebaseCore/Tests/SwiftUnit/**/*.h',

FirebaseCore/Tests/Unit/FIRAppTest.m

@@ -65,6 +65,7 @@ - (void)setUp {
   [super setUp];
   [FIROptions resetDefaultOptions];
   [FIRApp resetApps];
+  // TODO: Don't mock the class we are testing.
   _appClassMock = OCMClassMock([FIRApp class]);
   _observerMock = OCMObserverMock();
   _mockCoreDiagnosticsConnector = OCMClassMock([FIRCoreDiagnosticsConnector class]);
@@ -81,7 +82,14 @@ - (void)setUp {
 }
 
 - (void)tearDown {
+  // Wait for background operations to complete.
+  NSDate *waitUntilDate = [NSDate dateWithTimeIntervalSinceNow:0.5];
+  while ([[NSDate date] compare:waitUntilDate] == NSOrderedAscending) {
+    [[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:0.1]];
+  }
+
   [_appClassMock stopMocking];
+  _appClassMock = nil;
   [_notificationCenter removeObserver:_observerMock];
   _observerMock = nil;
   _notificationCenter = nil;