Issue title: Working settings
 Issue body: These settings worked for me.

melissa75@example.com

## functions\package.json

```json
{
  "name": "functions",
  "description": "Cloud Functions for Firebase",
  "scripts": {
    "lint": "eslint .",
    "serve": "firebase serve --only functions",
    "shell": "firebase functions:shell",
    "start": "npm run shell",
    "deploy": "firebase deploy --only functions",
    "logs": "firebase functions:log",
    "test": "mocha --timeout 10000",
    "test_all": "mocha test_all.js --timeout 10000"
  },
  "engines": {
    "node": "8"
  },
  "dependencies": {
    "file-system": "2.2.2",
    "firebase-admin": "8.8.0",
    "firebase-functions": "3.3.0"
  },
  "devDependencies": {
    "@firebase/testing": "0.16.3",
    "eslint": "^5.12.0",
    "eslint-plugin-promise": "^4.0.1",
    "firebase-functions-test": "0.1.7",
    "mocha": "6.2.2"
  },
  "private": true
}
```

## public\index.html

```html
<script src="/__/firebase/7.6.0/firebase-app.js"></script>
<script src="/__/firebase/7.6.0/firebase-auth.js"></script>
<script src="/__/firebase/7.6.0/firebase-firestore.js"></script>
<script src="/__/firebase/init.js"></script>
```

## Links

### 1. Getting started with the Firebase Local Emulator Suite

https://google.dev/codelabs/firebase-emulator-get-started?playlist-id=firebase-emulators#0

### 2. Test-drive Firestore Security Rules

https://google.dev/codelabs/firebase-emulator-test-rules#0

### 3. Test-drive Complex Firebase Functions

https://google.dev/codelabs/firebase-emulators-test-functions#0

 Comments: 
 Comment 0: I found a few problems with this issue:
  * I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.
  * This issue does not seem to follow the issue template. Make sure you provide all the required information.
 Comment 1: @yuchenshi I am surprised to see this issue given that it's `0.16.3` of the `@firebase/testing` SDK.  Can you check it out?
 Comment 2: I cannot reproduce this. A few things to try though:

1. Please check node and npm version. Try `npm install -g npm@latest`
1. `rm -r node_modules` in functions and `npm install` again.
1. `npm ls` and attach the output
 Comment 3: Okay I can now reproduce it. It turned out that I just forget to update to the latest master. I'll take a deeper dive.
 Comment 4: I've updated `@firebase/testing` on master. Thanks.

The reason was that `@melissa75@example.com` pulls in `melissa75@example.com`, which is one major version less than 7. However, `melissa75@example.com` pulls in `@melissa75@example.com` which only works with `firebase@7`.


```
├─┬ @melissa75@example.com
│ ├── @melissa75@example.com
│ ├─┬ @melissa75@example.com
│ ├─┬ melissa75@example.com
│ │ ├─┬ @melissa75@example.com
│ │ │ ├── @melissa75@example.com
│ │ │ ├── @melissa75@example.com
│ │ │ ├─┬ @melissa75@example.com
│ │ ├── @melissa75@example.com
│ │ ├─┬ @melissa75@example.com
│ │ │ └── @melissa75@example.com
│ │ ├─┬ @melissa75@example.com
│ │ │ ├── @melissa75@example.com
│ │ │ ├── @melissa75@example.com
│ │ │ ├── @melissa75@example.com deduped
│ │ ├─┬ @melissa75@example.com
│ │ │ ├── @melissa75@example.com
│ │ │ ├── @melissa75@example.com
│ │ │ ├─┬ @melissa75@example.com
│ │ │ ├── @melissa75@example.com
│ │ ├─┬ @melissa75@example.com
│ │ │ ├── @melissa75@example.com
│ │ │ ├── @melissa75@example.com
│ │ ├─┬ @melissa75@example.com
│ │ │ ├── @melissa75@example.com
│ │ │ ├─┬ @melissa75@example.com
│ │ ├─┬ @melissa75@example.com
│ │ │ ├── @melissa75@example.com deduped
│ │ │ ├─┬ @melissa75@example.com
│ │ ├─┬ @melissa75@example.com
│ │ │ ├── @melissa75@example.com deduped
│ │ │ ├── @melissa75@example.com
│ │ │ ├── @melissa75@example.com
│ │ │ ├─┬ @melissa75@example.com
│ │ ├─┬ @melissa75@example.com
│ │ ├─┬ @melissa75@example.com
│ │ │ ├── @melissa75@example.com
│ │ │ ├─┬ @melissa75@example.com
│ │ └─┬ @melissa75@example.com
├─┬ melissa75@example.com
│ ├─┬ @melissa75@example.com
│ │ ├─┬ @melissa75@example.com
│ │ │ ├── @melissa75@example.com deduped
│ │ ├─┬ @melissa75@example.com
│ │ │ └── @melissa75@example.com
│ │ ├── @melissa75@example.com
│ │ ├─┬ @melissa75@example.com
│ ├─┬ @melissa75@example.com
├─┬ melissa75@example.com
├─┬ melissa75@example.com
```

{'source': 'GithubIssues', 'repo_name_with_owner': 'firebase/firebase-js-sdk', 'issue_id': 539944606, 'repo_stars': 4447.0}