create sample count test cases (#6506)

Author: milaGGL

packages/firestore/test/integration/api/count.test.ts

@@ -0,0 +1,53 @@
+/**
+ * @license
+ * Copyright 2022 Google LLC
+ *
+ * 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 { expect } from 'chai';
+import {
+  countQuery,
+  getAggregateFromServerDirect,
+  query
+} from '../util/firebase_export';
+import { apiDescribe, withTestCollection } from '../util/helpers';
+
+apiDescribe('Aggregation COUNT query:', (persistence: boolean) => {
+  it('empty collection count equals to 0', () => {
+    const testDocs = {};
+    return withTestCollection(persistence, testDocs, collection => {
+      const countQuery_ = countQuery(query(collection));
+      return getAggregateFromServerDirect(countQuery_).then(snapshot => {
+        expect(snapshot.getCount()).to.equal(0);
+      });
+    });
+  });
+
+  it('test collection count equals to 6', () => {
+    const testDocs = {
+      a: { k: 'a' },
+      b: { k: 'b' },
+      c: { k: 'c' },
+      d: { k: 'd' },
+      e: { k: 'e' },
+      f: { k: 'f' }
+    };
+    return withTestCollection(persistence, testDocs, collection => {
+      const countQuery_ = countQuery(query(collection));
+      return getAggregateFromServerDirect(countQuery_).then(snapshot => {
+        expect(snapshot.getCount()).to.equal(6);
+      });
+    });
+  });
+});