firebase-ios-sdk/Firestore/Example/Tests/Integration/FSTTransactionTests.mm

/*
 * Copyright 2017 Google
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#import <FirebaseFirestore/FirebaseFirestore.h>

#import <XCTest/XCTest.h>
#include <libkern/OSAtomic.h>

#import "Firestore/Example/Tests/Util/FSTIntegrationTestCase.h"

@interface FSTTransactionTests : FSTIntegrationTestCase
@end

@implementation FSTTransactionTests

- (void)testGetDocuments {
  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc = [[firestore collectionWithPath:@"spaces"] documentWithAutoID];
  [self writeDocumentRef:doc data:@{@"foo" : @1, @"desc" : @"Stuff", @"owner" : @"Jonny"}];

  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
        [transaction getDocument:doc error:error];
        XCTAssertNil(*error);
        return @YES;
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        XCTAssertNil(result);
        // We currently require every document read to also be written.
        // TODO(b/34879758): Fix this check once we drop that requirement.
        XCTAssertNotNil(error);
        XCTAssertEqual(error.code, FIRFirestoreErrorCodeInvalidArgument);
        [expectation fulfill];
      }];
  [self awaitExpectations];
}

- (void)testDeleteDocument {
  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc = [[firestore collectionWithPath:@"towns"] documentWithAutoID];
  [self writeDocumentRef:doc data:@{@"foo" : @"bar"}];
  FIRDocumentSnapshot *snapshot = [self readDocumentForRef:doc];
  XCTAssertEqualObjects(@"bar", snapshot[@"foo"]);

  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
        [transaction deleteDocument:doc];
        return @YES;
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        XCTAssertEqualObjects(@YES, result);
        XCTAssertNil(error);
        [expectation fulfill];
      }];
  [self awaitExpectations];

  snapshot = [self readDocumentForRef:doc];
  XCTAssertFalse(snapshot.exists);
}

- (void)testGetNonexistentDocumentThenCreate {
  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc = [[firestore collectionWithPath:@"towns"] documentWithAutoID];

  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
        FIRDocumentSnapshot *snapshot = [transaction getDocument:doc error:error];
        XCTAssertNil(*error);
        XCTAssertNotNil(snapshot);
        XCTAssertFalse(snapshot.exists);
        [transaction setData:@{@"foo" : @"bar"} forDocument:doc];
        return @YES;
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        XCTAssertEqualObjects(@YES, result);
        XCTAssertNil(error);
        [expectation fulfill];
      }];
  [self awaitExpectations];

  FIRDocumentSnapshot *snapshot = [self readDocumentForRef:doc];
  XCTAssertTrue(snapshot.exists);
  XCTAssertEqualObjects(@"bar", snapshot[@"foo"]);
}

- (void)testGetNonexistentDocumentThenFailPatch {
  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc = [[firestore collectionWithPath:@"towns"] documentWithAutoID];

  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
        FIRDocumentSnapshot *snapshot = [transaction getDocument:doc error:error];
        XCTAssertNil(*error);
        XCTAssertFalse(snapshot.exists);
        [transaction updateData:@{@"foo" : @"bar"} forDocument:doc];
        return @YES;
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        XCTAssertNil(result);
        XCTAssertNotNil(error);
        XCTAssertEqualObjects(error.domain, FIRFirestoreErrorDomain);
        XCTAssertEqual(error.code, FIRFirestoreErrorCodeInvalidArgument);
        [expectation fulfill];
      }];
  [self awaitExpectations];
}

- (void)testDeleteDocumentAndPatch {
  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc = [[firestore collectionWithPath:@"towns"] documentWithAutoID];
  [self writeDocumentRef:doc data:@{@"foo" : @"bar"}];

  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id(FIRTransaction *transaction, NSError **error) {
        FIRDocumentSnapshot *snapshot = [transaction getDocument:doc error:error];
        XCTAssertNil(*error);
        XCTAssertTrue(snapshot.exists);
        [transaction deleteDocument:doc];
        // Since we deleted the doc, the update will fail
        [transaction updateData:@{@"foo" : @"bar"} forDocument:doc];
        return @YES;
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        XCTAssertNil(result);
        XCTAssertNotNil(error);
        XCTAssertEqualObjects(error.domain, FIRFirestoreErrorDomain);
        XCTAssertEqual(error.code, FIRFirestoreErrorCodeInvalidArgument);
        [expectation fulfill];
      }];
  [self awaitExpectations];
}

- (void)testDeleteDocumentAndSet {
  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc = [[firestore collectionWithPath:@"towns"] documentWithAutoID];
  [self writeDocumentRef:doc data:@{@"foo" : @"bar"}];

  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id(FIRTransaction *transaction, NSError **error) {
        FIRDocumentSnapshot *snapshot = [transaction getDocument:doc error:error];
        XCTAssertNil(*error);
        XCTAssertTrue(snapshot.exists);
        [transaction deleteDocument:doc];
        // TODO(dimond): In theory this should work, but it's complex to make it work, so instead we
        // just let the transaction fail and verify it's unsupported for now
        [transaction setData:@{@"foo" : @"new-bar"} forDocument:doc];
        return @YES;
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        XCTAssertNil(result);
        XCTAssertNotNil(error);
        XCTAssertEqualObjects(error.domain, FIRFirestoreErrorDomain);
        // This is the error surfaced by the backend.
        XCTAssertEqual(error.code, FIRFirestoreErrorCodeInvalidArgument);
        [expectation fulfill];
      }];
  [self awaitExpectations];
}

- (void)testWriteDocumentTwice {
  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc = [[firestore collectionWithPath:@"towns"] documentWithAutoID];

  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id(FIRTransaction *transaction, NSError **error) {
        [transaction setData:@{@"a" : @"b"} forDocument:doc];
        [transaction setData:@{@"c" : @"d"} forDocument:doc];
        return @YES;
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        XCTAssertEqualObjects(@YES, result);
        XCTAssertNil(error);
        [expectation fulfill];
      }];
  [self awaitExpectations];

  FIRDocumentSnapshot *snapshot = [self readDocumentForRef:doc];
  XCTAssertEqualObjects(snapshot.data, @{@"c" : @"d"});
}

- (void)testSetDocumentWithMerge {
  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc = [[firestore collectionWithPath:@"towns"] documentWithAutoID];

  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
        [transaction setData:@{@"a" : @"b", @"nested" : @{@"a" : @"b"}} forDocument:doc];
        [transaction setData:@{@"c" : @"d", @"nested" : @{@"c" : @"d"}} forDocument:doc merge:YES];
        return @YES;
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        XCTAssertEqualObjects(@YES, result);
        XCTAssertNil(error);
        [expectation fulfill];
      }];
  [self awaitExpectations];

  FIRDocumentSnapshot *snapshot = [self readDocumentForRef:doc];
  XCTAssertEqualObjects(snapshot.data,
                        (@{@"a" : @"b", @"c" : @"d", @"nested" : @{@"a" : @"b", @"c" : @"d"}}));
}

- (void)testCannotUpdateNonExistentDocument {
  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc = [[firestore collectionWithPath:@"towns"] documentWithAutoID];

  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
        [transaction updateData:@{@"foo" : @"bar"} forDocument:doc];
        return nil;
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        XCTAssertNotNil(error);
        // This is the error surfaced by the backend.
        XCTAssertEqual(error.code, FIRFirestoreErrorCodeNotFound);
        [expectation fulfill];
      }];
  [self awaitExpectations];

  FIRDocumentSnapshot *result = [self readDocumentForRef:doc];
  XCTAssertFalse(result.exists);
}

- (void)testIncrementTransactionally {
  // A barrier to make sure every transaction reaches the same spot.
  dispatch_semaphore_t writeBarrier = dispatch_semaphore_create(0);
  __block volatile int32_t started = 0;

  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc = [[firestore collectionWithPath:@"counters"] documentWithAutoID];
  [self writeDocumentRef:doc data:@{@"count" : @(5.0)}];

  // Make 3 transactions that will all increment.
  int total = 3;
  for (int i = 0; i < total; i++) {
    XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
    [firestore
        runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
          FIRDocumentSnapshot *snapshot = [transaction getDocument:doc error:error];
          XCTAssertNil(*error);
          int32_t nowStarted = OSAtomicIncrement32(&started);
          // Once all of the transactions have read, allow the first write.
          if (nowStarted == total) {
            dispatch_semaphore_signal(writeBarrier);
          }

          dispatch_semaphore_wait(writeBarrier, DISPATCH_TIME_FOREVER);
          // Refill the barrier so that the other transactions and retries succeed.
          dispatch_semaphore_signal(writeBarrier);

          double newCount = ((NSNumber *)snapshot[@"count"]).doubleValue + 1.0;
          [transaction setData:@{@"count" : @(newCount)} forDocument:doc];
          return @YES;
        }
        completion:^(id _Nullable result, NSError *_Nullable error) {
          [expectation fulfill];
        }];
  }

  [self awaitExpectations];
  // Now all transaction should be completed, so check the result.
  FIRDocumentSnapshot *snapshot = [self readDocumentForRef:doc];
  XCTAssertEqualObjects(@(5.0 + total), snapshot[@"count"]);
}

- (void)testUpdateTransactionally {
  // A barrier to make sure every transaction reaches the same spot.
  dispatch_semaphore_t writeBarrier = dispatch_semaphore_create(0);
  __block volatile int32_t started = 0;

  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc = [[firestore collectionWithPath:@"counters"] documentWithAutoID];
  [self writeDocumentRef:doc data:@{@"count" : @(5.0), @"other" : @"yes"}];

  // Make 3 transactions that will all increment.
  int total = 3;
  for (int i = 0; i < total; i++) {
    XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
    [firestore
        runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
          FIRDocumentSnapshot *snapshot = [transaction getDocument:doc error:error];
          XCTAssertNil(*error);
          int32_t nowStarted = OSAtomicIncrement32(&started);
          // Once all of the transactions have read, allow the first write.
          if (nowStarted == total) {
            dispatch_semaphore_signal(writeBarrier);
          }

          dispatch_semaphore_wait(writeBarrier, DISPATCH_TIME_FOREVER);
          // Refill the barrier so that the other transactions and retries succeed.
          dispatch_semaphore_signal(writeBarrier);

          double newCount = ((NSNumber *)snapshot[@"count"]).doubleValue + 1.0;
          [transaction updateData:@{@"count" : @(newCount)} forDocument:doc];
          return @YES;
        }
        completion:^(id _Nullable result, NSError *_Nullable error) {
          [expectation fulfill];
        }];
  }

  [self awaitExpectations];
  // Now all transaction should be completed, so check the result.
  FIRDocumentSnapshot *snapshot = [self readDocumentForRef:doc];
  XCTAssertEqualObjects(@(5.0 + total), snapshot[@"count"]);
  XCTAssertEqualObjects(@"yes", snapshot[@"other"]);
}

- (void)testHandleReadingOneDocAndWritingAnother {
  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc1 = [[firestore collectionWithPath:@"counters"] documentWithAutoID];
  FIRDocumentReference *doc2 = [[firestore collectionWithPath:@"counters"] documentWithAutoID];

  [self writeDocumentRef:doc1 data:@{@"count" : @(15.0)}];

  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
        // Get the first doc.
        [transaction getDocument:doc1 error:error];
        XCTAssertNil(*error);
        // Do a write outside of the transaction. The first time the
        // transaction is tried, this will bump the version, which
        // will cause the write to doc2 to fail. The second time, it
        // will be a no-op and not bump the version.
        dispatch_semaphore_t writeSemaphore = dispatch_semaphore_create(0);
        [doc1 setData:@{
          @"count" : @(1234)
        }
            completion:^(NSError *_Nullable error) {
              dispatch_semaphore_signal(writeSemaphore);
            }];
        // We can block on it, because transactions run on a background queue.
        dispatch_semaphore_wait(writeSemaphore, DISPATCH_TIME_FOREVER);
        // Now try to update the other doc from within the transaction.
        // This should fail once, because we read 15 earlier.
        [transaction setData:@{@"count" : @(16)} forDocument:doc2];
        return nil;
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        // We currently require every document read to also be written.
        // TODO(b/34879758): Add this check back once we drop that.
        // NSError *error = nil;
        // FIRDocument *snapshot = [transaction getDocument:doc1 error:&error];
        // XCTAssertNil(error);
        // XCTAssertEquals(0, tries);
        // XCTAssertEqualObjects(@(1234), snapshot[@"count"]);
        // snapshot = [transaction getDocument:doc2 error:&error];
        // XCTAssertNil(error);
        // XCTAssertEqualObjects(@(16), snapshot[@"count"]);
        XCTAssertNotNil(error);
        XCTAssertEqual(error.code, FIRFirestoreErrorCodeInvalidArgument);
        [expectation fulfill];
      }];
  [self awaitExpectations];
}

- (void)testReadingADocTwiceWithDifferentVersions {
  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc = [[firestore collectionWithPath:@"counters"] documentWithAutoID];
  [self writeDocumentRef:doc data:@{@"count" : @(15.0)}];
  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
        // Get the doc once.
        FIRDocumentSnapshot *snapshot = [transaction getDocument:doc error:error];
        XCTAssertNil(*error);
        XCTAssertEqualObjects(@(15), snapshot[@"count"]);
        // Do a write outside of the transaction.
        dispatch_semaphore_t writeSemaphore = dispatch_semaphore_create(0);
        [doc setData:@{
          @"count" : @(1234)
        }
            completion:^(NSError *_Nullable error) {
              dispatch_semaphore_signal(writeSemaphore);
            }];
        // We can block on it, because transactions run on a background queue.
        dispatch_semaphore_wait(writeSemaphore, DISPATCH_TIME_FOREVER);
        // Get the doc again in the transaction with the new version.
        snapshot = [transaction getDocument:doc error:error];
        // The get itself will fail, because we already read an earlier version of this document.
        // TODO(klimt): Perhaps we shouldn't fail reads for this, but should wait and fail the
        // whole transaction? It's an edge-case anyway, as developers shouldn't be reading the same
        // doc multiple times. But they need to handle read errors anyway.
        XCTAssertNotNil(*error);
        return nil;
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        [expectation fulfill];
        XCTAssertNotNil(error);
        XCTAssertEqual(error.code, FIRFirestoreErrorCodeAborted);
      }];
  [self awaitExpectations];

  FIRDocumentSnapshot *snapshot = [self readDocumentForRef:doc];
  XCTAssertEqualObjects(@(1234.0), snapshot[@"count"]);
}

- (void)testReadAndUpdateNonExistentDocumentWithExternalWrite {
  FIRFirestore *firestore = [self firestore];
  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
        // Get and update a document that doesn't exist so that the transaction fails.
        FIRDocumentReference *doc =
            [[firestore collectionWithPath:@"nonexistent"] documentWithAutoID];
        [transaction getDocument:doc error:error];
        XCTAssertNil(*error);
        // Do a write outside of the transaction.
        dispatch_semaphore_t writeSemaphore = dispatch_semaphore_create(0);
        [doc setData:@{
          @"count" : @(1234)
        }
            completion:^(NSError *_Nullable error) {
              dispatch_semaphore_signal(writeSemaphore);
            }];
        // We can block on it, because transactions run on a background queue.
        dispatch_semaphore_wait(writeSemaphore, DISPATCH_TIME_FOREVER);
        // Now try to update the other doc from within the transaction.
        // This should fail, because the document didn't exist at the
        // start of the transaction.
        [transaction updateData:@{@"count" : @(16)} forDocument:doc];
        return nil;
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        [expectation fulfill];
        XCTAssertNotNil(error);
        XCTAssertEqual(error.code, FIRFirestoreErrorCodeInvalidArgument);
      }];
  [self awaitExpectations];
}

- (void)testCannotHaveAGetWithoutMutations {
  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc = [[firestore collectionWithPath:@"foo"] documentWithAutoID];
  [self writeDocumentRef:doc data:@{@"foo" : @"bar"}];
  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
        FIRDocumentSnapshot *snapshot = [transaction getDocument:doc error:error];
        XCTAssertTrue(snapshot.exists);
        XCTAssertNil(*error);
        return nil;
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        // We currently require every document read to also be written.
        // TODO(b/34879758): Fix this check once we drop that requirement.
        XCTAssertNotNil(error);
        XCTAssertEqual(error.code, FIRFirestoreErrorCodeInvalidArgument);
        [expectation fulfill];
      }];
  [self awaitExpectations];
}

- (void)testSuccessWithNoTransactionOperations {
  FIRFirestore *firestore = [self firestore];
  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
        return @"yes";
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        XCTAssertEqualObjects(@"yes", result);
        XCTAssertNil(error);
        [expectation fulfill];
      }];
  [self awaitExpectations];
}

- (void)testCancellationOnError {
  FIRFirestore *firestore = [self firestore];
  FIRDocumentReference *doc = [[firestore collectionWithPath:@"towns"] documentWithAutoID];
  __block volatile int32_t count = 0;
  XCTestExpectation *expectation = [self expectationWithDescription:@"transaction"];
  [firestore
      runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
        OSAtomicIncrement32(&count);
        [transaction setData:@{@"foo" : @"bar"} forDocument:doc];
        if (error) {
          *error = [NSError errorWithDomain:NSCocoaErrorDomain code:35 userInfo:@{}];
        }
        return nil;
      }
      completion:^(id _Nullable result, NSError *_Nullable error) {
        XCTAssertNil(result);
        XCTAssertNotNil(error);
        XCTAssertEqual(35, error.code);
        [expectation fulfill];
      }];
  [self awaitExpectations];
  XCTAssertEqual(1, (int)count);
  FIRDocumentSnapshot *snapshot = [self readDocumentForRef:doc];
  XCTAssertFalse(snapshot.exists);
}

- (void)testUpdateFieldsWithDotsTransactionally {
  FIRDocumentReference *doc = [self documentRef];

  XCTestExpectation *expectation =
      [self expectationWithDescription:@"testUpdateFieldsWithDotsTransactionally"];

  [doc.firestore
      runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
        XCTAssertNil(*error);
        [transaction setData:@{@"a.b" : @"old", @"c.d" : @"old"} forDocument:doc];
        [transaction updateData:@{
          [[FIRFieldPath alloc] initWithFields:@[ @"a.b" ]] : @"new"
        }
                    forDocument:doc];
        return nil;
      }
      completion:^(id result, NSError *error) {
        XCTAssertNil(error);
        [doc getDocumentWithCompletion:^(FIRDocumentSnapshot *snapshot, NSError *error) {
          XCTAssertNil(error);
          XCTAssertEqualObjects(snapshot.data, (@{@"a.b" : @"new", @"c.d" : @"old"}));
        }];
        [expectation fulfill];
      }];
  [self awaitExpectations];
}

- (void)testUpdateNestedFieldsTransactionally {
  FIRDocumentReference *doc = [self documentRef];

  XCTestExpectation *expectation =
      [self expectationWithDescription:@"testUpdateNestedFieldsTransactionally"];

  [doc.firestore
      runTransactionWithBlock:^id _Nullable(FIRTransaction *transaction, NSError **error) {
        XCTAssertNil(*error);
        [transaction setData:@{
          @"a" : @{@"b" : @"old"},
          @"c" : @{@"d" : @"old"},
          @"e" : @{@"f" : @"old"}
        }
                 forDocument:doc];
        [transaction updateData:@{
          @"a.b" : @"new",
          [[FIRFieldPath alloc] initWithFields:@[ @"c", @"d" ]] : @"new"
        }
                    forDocument:doc];
        return nil;
      }
      completion:^(id result, NSError *error) {
        XCTAssertNil(error);
        [doc getDocumentWithCompletion:^(FIRDocumentSnapshot *snapshot, NSError *error) {
          XCTAssertNil(error);
          XCTAssertEqualObjects(snapshot.data, (@{
                                  @"a" : @{@"b" : @"new"},
                                  @"c" : @{@"d" : @"new"},
                                  @"e" : @{@"f" : @"old"}
                                }));
        }];
        [expectation fulfill];
      }];
  [self awaitExpectations];
}

@end