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🚀 TDD, Where Did It All Go Wrong (Ian Cooper)

DevTernity Conference · talk · Watch on YouTube

Testing, debugging & developer toolsSoftware practice, open source & careers

What it is

Ian Cooper's DevTernity talk revisits Kent Beck's original TDD ideas and shows where misunderstandings crept in. It argues tests should target behaviors through public interfaces rather than implementation details, so suites support refactoring instead of resisting it.

Why Hacker News recommends it

HN repeatedly calls it the best talk on testing, and many say it changed how they approach tests, mocks and the meaning of a unit.

  • 11 people recommended it
  • 11 different months
  • 5 strong recommendations
  • first 2018, last 2024

What HN commenters said

  1. “please watch Ian Cooper's "TDD, Where Did It All Go Wrong”

    Explains why testing public interfaces beats testing internals.

    macca321, 2018-11 · Strong recommendation · in “Signs you are doing continuous testing wrong”

  2. “The best talk on this topic, IMO is Ian Cooper: "TDD, Where did it all go wrong?”

    Best talk on TDD, restoring original principles.

    VHRanger, 2020-08 · Strong recommendation · in “Is TDD Dead? (2014)”

  3. “This excellent talk completely changed the way I approached testing. Every developer who writes tests needs to watch this now!”

    Changed how commenter approaches testing; mocking everything blocks refactoring.

    globular-toast, 2021-03 · Strong recommendation · in “CUPID – the back story”

  4. “describes my own experiences with automated testing quite well.”

    Matches commenter's experience with automated testing; pragmatic, empirical testing advice.

    chriswarbo, 2019-05 · Recommendation · in “Ask HN: What overlooked class of tools should a self-taught programmer look into”

  5. “Recommend”

    Shows tests that enable refactoring rather than resisting it.

    benjiweber, 2019-05 · Recommendation · in “Is High Quality Software Worth the Cost?”

  6. “Mandatory link to”

    Clarifies testing points; warns against overusing mocks.

    beders, 2020-09 · Recommendation · in “Best Practices for Testing in Java (2019)”

  7. “TDD: where did it all go wrong.”

    Explains unit as module, not function, and overfitted tests.

    snidane, 2021-03 · Recommendation · in “CUPID – the back story”

  8. “That's the right way to do TDD, see this talk”

    Explains behavior-focused TDD that allows fearless refactoring

    imran-iq, 2022-08 · Recommendation · in “I have complicated feelings about TDD”

Excerpts from Hacker News comments, linked to the originals. Summaries and labels were written by a language model from those comments.

Topics: tdd, unit testing, mocking, refactoring, kent beck, bdd

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