@firebase/testing doesn't return firestore() instance when firebase-admin is a dependency

[stamler]

Environment

• Operating System version: macOS 10.14.4
• Browser version: Safari 12.1
• Firebase SDK version: @firebase/testing 0.7.9 through 0.9.4
• Firebase Product: @firebase/testing and firebase-admin

Description

This is a refinement and isolation of issue #1630 specifically related to firebase-admin breaking @firebase/testing. Even if no code is called in firebase-admin the issue still presents.

@firebase/testing doesn't return a firestore() instance when firebase-admin is a dependency in package.json.

Steps to reproduce

1. git clone https://github.com/firebase/quickstart-nodejs.git
2. cd quickstart-nodejs/firestore-emulator/javascript-quickstart/
3. add "firebase-admin": "7.3.0" to "dependencies" in package.json. This is the step which reproduces the issue
4. npm install
5. firebase serve --only firestore

Now in the node the run the following code:
const firebase = require("@firebase/testing");
firebase.firestore()

This will produce an error:
Thrown:
TypeError: firebase.firestore is not a function

[google-oss-bot]

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[themikejr]

I have encountered this issue as well.

[Feiyang1]

Firebase JS SDK and Firebase Admin SDK have some compatibility issues.
I provided detailed explanation and workarounds in #1696 (comment)

Hope it helps.

[akauppi]

Note to people seeing this after 2019: @firebase/testing is now @firebase/rules-unit-testing