add test

Author: wu-hui

packages/firestore/src/lite-api/database.ts

@@ -302,18 +302,21 @@ export function connectFirestoreEmulator(
   firestore = cast(firestore, Firestore);
   const settings = firestore._getSettings();
 
+  logWarn(`before connect emulator, settings is {JSON.stringify(settings)}`);
   if (settings.host !== DEFAULT_HOST && settings.host !== host) {
     logWarn(
       'Host has been set in both settings() and useEmulator(), emulator host ' +
         'will be used'
     );
   }
 
-  firestore._setSettings({
+  const newSettings = {
     ...settings,
     host: `${host}:${port}`,
     ssl: false
-  });
+  };
+  logWarn(`after connect emulator, settings is ${JSON.stringify(newSettings)}`);
+  firestore._setSettings(newSettings);
 
   if (options.mockUserToken) {
     let token: string;

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

@@ -29,7 +29,9 @@ import {
   enableIndexedDbPersistence,
   setDoc,
   memoryLocalCache,
-  getDocFromCache
+  getDocFromCache,
+  persistentLocalCache,
+  connectFirestoreEmulator
 } from '../util/firebase_export';
 import { DEFAULT_SETTINGS } from '../util/settings';
 
@@ -141,6 +143,25 @@ describe('Firestore Provider', () => {
     });
   });
 
+  it.only('connectFirestoreEmulator() keeps other settings', async () => {
+    const app = initializeApp(
+      { apiKey: 'fake-api-key', projectId: 'test-project' },
+      'test-use-enablePersistence'
+    );
+    const db = initializeFirestore(app, {
+      ...DEFAULT_SETTINGS,
+      localCache: persistentLocalCache()
+    });
+    connectFirestoreEmulator(db, "localhost", 8080);
+
+    // SDK still functions.
+    // eslint-disable-next-line @typescript-eslint/no-floating-promises
+    setDoc(doc(db, 'coll/doc'), { field: 'foo' });
+    expect((await getDocFromCache(doc(db, 'coll/doc'))).data()).to.deep.equal({
+      field: 'foo'
+    });
+  });
+
   it('cannot mix enableIndexedDbPersistence() and settings.cache', async () => {
     const app = initializeApp(
       { apiKey: 'fake-api-key', projectId: 'test-project' },