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Comment on How do you get your team to write tests?

Focusing on code coverage (which doesn’t distinguish between more and less important parts of the code) seems like the opposite of your very good (IMO) recommendation in another comment to focus on specific high-value use-cases.

From my experience it’s far easier to sell the need for specific tests if they are framed as “we need assurances that this component does not fail under conceivable usecases” and specially as “we were screwed by this bug and we need to be absolutely sure we don’t experience it ever again.”

Code coverage is an OK metric and I agree with tracking it, but I wouldn’t recommend making it a target. It might force developers to write tests, but it probably won’t convince them. And as a developer I hate feeling “forced” and prefer if at all possible to use consensus to decide on team practices.

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lysdexic@programming.dev ⁨1⁩ ⁨year⁩ ago

Focusing on code coverage (which doesn’t distinguish between more and less important parts of the code) seems like the opposite of your very good (IMO) recommendation in another comment to focus on specific high-value use-cases.

The usefulness of code coverage ratios is to drive the conversation on the need to track invariants and avoid regressions. I agree it’s very easy to interpret a metric as a target to optimize, but in this context coverage ratios is primarily used to raise the question on why wasn’t a unit test added.

It’s counterproductive to aim for ~100% but without this indicator any question or concern regarding missing tests will feel arbitrary. With coverage ratios being tracked, this topic becomes systematic and helps build up a team culture that is test-driven or at least test-aware.

Code coverage is an OK metric and I agree with tracking it, but I wouldn’t recommend making it a target. It might force developers to write tests, but it probably won’t convince them.

True. Coverage ratios are an indicator, and they should never be an optimizable target. Hence the need to keep minimum coverage ratios low, so that the team has flexibility to manage them. Also important, have CICD pipelines export the full coverage report to track which parts of the code are not covered.

The goal is to have meaningful tests and mitigate risks, and have a system in place to develop a test-minded culture and help the team be mindful of the need to track specific invariants. Tests need to mean something and deliver value, and maximizing ratios is not it.

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