How to test an npm module with peerDependencies?

Question

I am new to understand peerDependencies, and I have read the following references seeking as to how to test an npm module contains peerDependencies within its package.json:

• Peer Dependencies
• Understanding the npm dependency model
• Common npm mistakes
• StackOverflow: npm peerDependencies during development

However, I have not found a clear solution for testing npm with peerDependencies. Some recommend adding the peerDependencies as globals, and some reference to include peerDependencies within devDependencies, and neither seems right.

For example, I have a package that has a peer dependency, a custom logger, and this logger needs to be configured by its host package before it can be used.

This is how I perform most tests scripted in using this Gulp task:

function testRunner() {
  return (
    gulp
      .src('./tests/**/*.js', { read: false })
      .pipe(
        mocha({
          exit: true,
          timeout: 10000
        })
      )
      .on('error', console.error)
  );
}

I did receive a helpful suggestion (see comments below, @estus) to use npm-install-peers, however, I am not yet certain if it can configure a peer dependency before usage, as it would be performed by the host package.

Feedback and Suggestions are most appreciated.

Answer 1

In my case, I developed a library last time that use ioredis as peer dependency. My solution was to put that library as well in dev dependency.

// package.json
"peerDependencies": {
    "ioredis": "4.x"
},
"devDependencies": {
    "ioredis": "4.x"
}

it worked well and no issue so far using this approach.