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A drop in replacement for tape that runs tests concurrently in node and the browser (using browserify).


npm install --save-dev mixed-tape tape /

yarn add -D mixed-tape tape


const tape = require('tape')
const mixedTape = require('mixed-tape')
const test = mixedTape(tape)
test('first test', t => {
  setTimeout(() => {
    t.equals(1, 1, 'why not?')
  }, 1000)
test('second test', t => {
  setTimeout(() => {
    t.ok(true, 'I will never fail')
  }, 1000)
// tests will run in ~1 second instead of ~2

Note that if you'd like to split your tests into separate files, mixed-tape should be created and exported in just one place, eg:

// test-runner.js
const tape = require('tape')
const mixedTape = require('mixed-tape')
module.exports = mixedTape(tape)
// test-file-1.spec.js
const test = require('./test-runner')
test('my first test', t => {
  // ...
// test-file-2.spec.js
const test = require('./test-runner')
test('my second test', t => {
  // ...

how does it work?

mixed-tape runs tests asynchronously on one thread. It saves lots of time for tests that rely on IO (eg. e2e tests). It can definitely run synchronous tests, but one will likely not see a big performance boost there.

Under the hood, it uses tape's createHarness method for every test it runs, piping their results (once the test has run) to a stream that reports them in real time, strips out their summaries and prints out a merged summary in the end.

It intentionally does not hijack console.logs. For this reason, those might appear before the test's assertions. This is done because it was deemed this is a less surprising behaviour to the developer, given the other options.

api support

  • test()

  • test.only()

  • test.skip()

  • test.onFinish()

  • test.onFailure()

  • test.createStream()

  • test.createHarness() - tape itself does not support recursive createHarness calls, so implementing this is not trivial. If this is a thing for you, please open an issue or better yet, a PR.

These methods work as expected. For full documentation, please see: tape.

use with care

While the prospect of running tests concurrently might be an appealing one (often reducing the run time of the test suite to not much more than the longest test), there are some serious caveats and dangers:

Tests will inevitably share some sort of state. Even if there are proper isolation methods in place, at the very least they will share hardware resources.

In a lot of cases this is not an issue, but be wary when using this method. With reduced speed come unknown variables.


Please do!



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