Test Driven Development (TDD) – Code Coverage

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TDD (Test Driven Development) Letters

Should you aim for 100% code coverage on Test Driven Development (TDD) projects?

My view is that for TDD projects, only the business logic layer should be under TDD, not every line of code in every layer. This way it gives you maximum benefit developing the core unique thing you are developing, and lets the common and garden plumbing in other layers be produced without 5 lines of test code for each line of application code produced.

Controversial? Many projects blindly use tools like NCrunch and aim for every line of code to be covered by a test somewhere.

I personally don’t think this is necessary and adds a lot of overhead to a project where if you are following SOLID or similar rules your MVC views will only contain formatting and your data access layer will contain lots of small very simple functions. So what if you miss a where clause off a select? It will be really obvious really quickly especially if the repository method is used in more than one place, and fixing it once will fix it everywhere. I think a balanced approach is much more productive, although like a lot of my views, these are strong views, weakly held – that is, the client can easily convince me that if they want to do it differently they can, because they are the client after all.

About Phil

I have been working as a software developer since 1983. This blog could have been called "From Fortran 77, C and Cobol to C# in 20 (not so) easy years", but it doesn't sound quite right somehow. Besides I'm talking about what's happened since 2003, not before!

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