update database integration tests

Author: paulb777

Example/Core/Tests/FIRComponentContainerTest.m

@@ -43,7 +43,7 @@ - (instancetype)initWithApp:(FIRApp *)app
                  components:(NSDictionary<NSString *, FIRComponentCreationBlock> *)components {
   self = [self initWithApp:app registrants:[[NSMutableSet alloc] init]];
   if (self) {
-    components = [components mutableCopy];
+    self.components = [components mutableCopy];
   }
   return self;
 }

Example/Database/Tests/Helpers/FIRFakeApp.m

@@ -39,6 +39,27 @@ @interface FIRDatabaseComponent (Internal)
 - (instancetype)initWithApp:(FIRApp *)app;
 @end
 
+@interface FIRComponentContainer (TestInternal)
+@property(nonatomic, strong) NSMutableDictionary<NSString *, FIRComponentCreationBlock> *components;
+@end
+
+@interface FIRComponentContainer (TestInternalImplementations)
+- (instancetype)initWithApp:(FIRApp *)app
+                 components:(NSDictionary<NSString *, FIRComponentCreationBlock> *)components;
+@end
+
+@implementation FIRComponentContainer (TestInternalImplementations)
+
+- (instancetype)initWithApp:(FIRApp *)app
+                 components:(NSDictionary<NSString *, FIRComponentCreationBlock> *)components {
+  self = [self initWithApp:app registrants:[[NSMutableSet alloc] init]];
+  if (self) {
+    self.components = [components mutableCopy];
+  }
+  return self;
+}
+@end
+
 @implementation FIRFakeApp
 
 - (instancetype)initWithName:(NSString *)name URL:(NSString *)url {