Detox Mocking：GitHub Actions中Metro Bundler的运行问题

Can I add APP_MOCK=mocked to the react-native run-ios command? #

Yes you can, but you need to ensure the environment variable is properly passed to the Metro Bundler process that run-ios spawns. Here's how to do it:

APP_MOCK=mocked npx react-native run-ios

If this didn't load your mock files as expected, it's likely due to one of these reasons:

• Your Metro configuration (metro.config.js) isn't reading process.env.APP_MOCK during startup to switch between real and mock files. Add a debug log at the top of your config to verify:

  console.log("Metro received APP_MOCK value:", process.env.APP_MOCK);
  

• In CI environments (like GitHub Actions), non-interactive shells sometimes have issues propagating environment variables to child processes. If this is the case, explicitely starting Metro first (see below) will be more reliable.

How to explicitly start Metro with the mock environment variable (better for CI) #

Instead of relying on run-ios to start Metro, split the steps to avoid the bundler卡顿 issue and ensure the environment variable is set correctly:

1. Start Metro in the background with the mock variable, and redirect logs for debugging:

   APP_MOCK=mocked npx react-native start > metro.log 2>&1 &
   

2. Wait for Metro to fully initialize (adjust the sleep time based on your project's startup speed):

   sleep 30
   

3. Run your iOS project:

   npx react-native run-ios
   

In GitHub Actions, this translates to:

- name: Start Metro Bundler with Mock Environment
  run: |
    APP_MOCK=mocked npx react-native start > metro.log 2>&1 &
    sleep 30

- name: Build and Run iOS App
  run: npx react-native run-ios

About opening a new terminal programmatically #

For local development, you could use shell scripts or Node.js tools to spawn a new terminal window, but this isn't necessary (or recommended) for CI environments. CI runs in a single shell session, so backgrounding the Metro process as shown above is the standard approach.

内容的提问来源于stack exchange，提问作者Roke