TDD Conference 2021 - On The Relationship Between Units Of Isolation And Test Coupling - Mario Cervera

TDD Conference 2021 - On The Relationship Between Units Of Isolation And Test Coupling - Mario Cervera

First International Test Driven Development took place on July 10th.

In this series, I will include every talk together with my notes and further reading.

Hopefully, a lot of readers will watch and rewatch the talks, as they are worth several reviews.

Let's continue...


Mario has been a software professional for more than a decade. He also conducted research in the field of Software Engineering, which allowed him to graduate as a PhD in Computer Science. As a strong advocate of software craftsmanship principles and values, he helps teams improve their technical practices so they can deliver higher-quality software at a sustainable pace.

TL;DR: Coupling leads to fragile tests.


My Personal notes

  • Fragility is the opposite to Robust when we talk about tests.
  • Fragile tests are tests that break when they should not break.
  • Tests are the specification of behaviour.
  • if we are not changing the observable behaviour of tests, and they break, the tests are preventing our refactorings.
  • We want to avoid, at all costs, fragile tests that fail when they shouldn't.
  • Coupling is the main cause of fragile tests.
  • Overspecified software makes more assumptions than necessary.
  • In a mocking approach, we need to change a lot of tests when we refactor.
  • if we make our attributes public to test them is a smell, we are testing accidental structure.
  • On Behavior-centric view, the true unit of isolation is not unit tests, but behaviour.
  • Refactoring is the key step in TDD.
  • Tests are code even more important than production code.

The outcome of this understanding is that a test-case per class approach fails to capture the ethos for TDD. Adding a new class is not the trigger for writing tests. The trigger is implementing a requirement.

Ian Cooper

Mario has also written an article on his talk. Please rush to read it here.

Speaker Links


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