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Marco Ippolito

Exploring Node.js�test runner

© Copyright 2023 NearForm Ltd. All Rights Reserved.

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Marco Ippolito

@satanacchio

Senior Developer Experience Engineer @NearForm

Core contributor @Node.js

Open Source Enthusiast

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@satanacchio

What’s a test runner?

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A test runner is a tool used to run or execute tests and export results

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It selects the source code directories and picks the test files to run

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A few examples…

  • JUnit

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A few examples…

  • JUnit

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  • pytest

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A few examples…

  • JUnit

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  • pytest

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  • go test

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A few examples…

  • JUnit

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  • pytest

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  • go test

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  • xUnit

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So cypress is a test runner right?

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Classification

  • Mocha is a test runner and a testing framework

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Test runners always include testing framework

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Classification

  • Mocha is a test runner and a testing framework

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  • Cypress is a testing framework (built on mocha)

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Classification

  • Mocha is a test runner and a testing framework

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  • Cypress is a testing framework (built on mocha)

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  • Chai is an assertion library (built on mocha)

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What about ?

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Why are there so many test runners?

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Node.js follows the “minimal core” principle, it delegates everything non essential to the ecosystem

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Improving developer experience and reducing surface for NPM supply chain attacks

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Node.js was shipping only an assertion library.

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Node.js was shipping only an assertion library. It needed a native test runner

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Node.js was shipping only an assertion library. It needed a native test runner, and a testing framework

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The test runner is stable and production ready�with Node 20

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We finally

made it!

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The test runner was inspired by node-tap

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Some features!

  • Filtering (only, skip, —test-name-pattern)

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Some features!

  • Filtering (only, skip, —test-name-pattern)
  • Subtest

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Some features!

  • Filtering (only, skip, —test-name-pattern)
  • Subtest
  • Reporting (tap, spec, dot, junit)

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@satanacchio

Some features!

  • Filtering (only, skip, —test-name-pattern)
  • Subtest
  • Reporting (tap, spec, dot, junit)
  • Mocking

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Some features!

  • Filtering (only, skip, —test-name-pattern)
  • Subtest
  • Reporting (tap, spec, dot, junit)
  • Mocking
  • Watch mode (--watch)

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Some features!

  • Filtering (only, skip, —test-name-pattern)
  • Subtest
  • Reporting (tap, spec, dot, junit)
  • Mocking
  • Watch mode (--watch)
  • Code coverage (--experimental-test-coverage)

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“Talk is cheap, show me the code!” - Linus Torvalds

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Should I migrate my existing test suite tomorrow?

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Cons

  • Small ecosystem (libraries built on top, guides)

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Cons

  • Small ecosystem (libraries built on top, guides)

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  • Fewer api compared to other test runners

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Cons

  • Small ecosystem (libraries built on top, guides)

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  • Fewer api compared to other test runners�
  • No typescript support (natively, you can use ts-node)

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Desired features

  • Planning

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Desired features

  • Planning

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  • Fake Timers

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Desired features

  • Planning

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  • Fake Timers

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The test runner is evolving fast!

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Desired features

  • Planning

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  • Fake Timers

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  • Exit on failure

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Desired features

  • Planning

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  • Fake Timers

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  • Exit on failure

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  • Expect failure

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