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To run the samples in this demo you will first need to run npm install from inside the repo root. All demos have npm scripts to simplify execution.

What is TAP?

  • TAP = Test Anything Protocol

    • Basic protocol created for testing Perl scripts.
    • Implementations in multiple languages
  • tap JS library written by Isaac Z. Schlueter (@izs, founder of npm)

    • All of npm's test are built on tap, long term support.
    • Pros:
      • Can detect a test timing out.
      • Each test runs in own child process, less risk of environment corruption
    • Cons:
      • Cannot do browser testing
  • tape JS library written by James Halliday (@substack, created Browserify)

    • Now has multiple maintainers and is used in hundreds of projects.
    • Pros:
      • Lighter-weight, faster.
      • Can be used in the browser.
    • Cons:
      • Most browser test centered around Browserify
      • No examples/tools for using with RequireJS
  • Both libraries consist of two parts:

    1. Testing Framework (require('tape').test)
    • Outputs TAP to stdout
    • All tests assumed to be asynchronous
    • test('name', function (t) {})
      • Nest test() calls for subtests, instead of define() and it()
    • t contains assertions and .end()
    • Meshes well with sinon
      • t.pass(spy.calledOnce)
    • Can also use chai assertions.
      • Anything thrown within the test() function gets registered as a failed assertion, just like in mocha.
      • Wrap chai assertions in a t.shouldNotThrow() function to prevent undone tests.
    1. Testing Harness (shell command)
    • Receives TAP from tests.
    • tap formats into clean output, add -C to get raw TAP
    • tape aggregates results into a single output, must be piped to formatter.
  • Both libraries can run each others tests.

    • For node testing there is a benefit to building tests with tape and running them with tap.
  • Tests can be parallelized using Prove, a Perl TAP harness.

    • Dunno why nobody has made a node based parallelized test runner.

Why use Tape over Mocha?

Example 1

  • Show index.js

    • Something wrong with this file, but don't look for it yet.
  • Show mocha/test.js

    • Walk through test structure, point out assertions.
  • npm run mocha

    • Show that test passes, everything looks good right?
  • Show tape/test.js

    • Same test structure, just different way of calling assertions.
  • npm run tape

    • Test is failing, why?
    • plan != count
  • node tape/test.js to get raw output

    • Tape tests are normal node processes that output TAP to stdout
    • Each assertion is enumerated with ok and not ok, indents for sub-tests.
    • t.plan(4) call identifies expected four total assertions
    • Count off assertions, only three ran.
    • Note that close connection is missing
    • Identify missing parens on closeConnection call in index.js
    • Add parens, re-run test. Ta da.
  • Show mocha/test-working.js

    • Mocha can be made to catch missing executions
    • Mock functions wrapped in sinon spies
    • Assertions that spies were called at end of test
    • Requires more effort, greater risk, complicates tests

Example 2

  • Show index2.js

    • Basic unit, semi-contrived example. Returns collection of data.
  • Show mocha/test2.js

    • Asserting that all three pieces of data pass.
  • npm run mocha2

    • Test fails at first assertion.
  • Show tape/test2.js

    • Exact same test.
  • npm run tape2

    • Outputs all three failing assertions.
    • Because tape doesn't rely on assertions, it doesn't fall down on the first failure, giving more useful output.


  • npm run cover

    • Show coverage folder.
  • npm run cover-mocha

    • Show coverage.
  • Both are created the same way through istanbul.

    • istanbul cover tape tape/*
    • istanbul cover _mocha mocha/*
      • Must use _mocha due to test runner isolation in mocha
      • tap runner has same problem, solves by bundling istanbul into itself


A short demonstration of why Tape makes for better testing than Mocha



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