FIRQueryTests.mm: begin porting resumingAQueryShouldUseExistenceFilterToDetectDeletes from firebase/firebase-android-sdk#4799

Author: dconeybe

Firestore/Example/Tests/Integration/API/FIRQueryTests.mm

@@ -1180,4 +1180,28 @@ - (void)testOrderByEquality {
                      matchesResult:@[ @"doc6", @"doc3" ]];
 }
 
+- (void)resumingAQueryShouldUseExistenceFilterToDetectDeletes {
+  // Prepare the names and contents of the 100 documents to create.
+  NSMutableDictionary<NSString*, NSDictionary<NSString *, id>*>* testData = [[NSMutableDictionary alloc] init];
+  for (int i=0; i<100; i++) {
+    [testData setValue:@{@"key": @42} forKey:[NSString stringWithFormat:@"doc%@", @(i)]];
+  }
+
+  // Create 100 documents in a new collection.
+  FIRCollectionReference *collRef = [self collectionRefWithDocuments:testData];
+
+  // Run a query to populate the local cache with the 100 documents and a resume token.
+  NSArray<FIRDocumentReference*>* createdDocuments;
+  {
+    FIRQuerySnapshot *querySnapshot = [self readDocumentSetForRef:collRef source:FIRFirestoreSourceDefault];
+    NSMutableArray<FIRDocumentReference*>* createdDocumentsAccumulator = [[NSMutableArray alloc] init];
+    for (FIRDocumentSnapshot* documentSnapshot in querySnapshot.documents) {
+      [createdDocumentsAccumulator addObject:documentSnapshot.reference];
+    }
+    createdDocuments = [createdDocumentsAccumulator copy];
+  }
+
+  (void)createdDocuments;
+}
+
 @end