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Is there such a thing as excessive unit testing?

Asked 2008-12-07T08:17:57.983
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I'm not brand new to the concept of unit testing but at the same time I've not yet mastered them either.

The one question that has been going through my head recently as I've been writing unit tests while writing my code using the TDD methodology is: to what level should I be testing?

Sometimes I wonder if I'm being excessive in the use of unit testing.

At what point should a developer stop writing unit tests and get actual work done?

I might need to clarify that question before people assume I'm against using TDD...

What I'm struggling with is the granularity of my test....

  • When my app has a config file do I test that values can be retrieved from the file? I lean towards yes....but....
  • Do I then write a unit test for each possible config value that will be present? ie check that they exist...and can be parsed to the correct type...
  • When my app writes errors to a log do I need to test that it is able to write to the log? Do I then need to write tests to verify that entries are actually made to the log?

I want to be able to use my unit tests to verify the behavior of my app...but I'm not quite sure where to stop. Is it possible to write tests that are too trivial?

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yes, unit testing can be taken to excess/extremes

keep in mind that it is only necessary to test features; everything else follows from that

so no, you don't have to test that you can read values from a config file, because one (or more) of the features will need to read values from a config file - and if they don't, then you don't need a config file!

EDIT: There seems to be some confusion as to what I am trying to say. I am not saying that unit testing and feature testing are the same thing - they are not. Per wikipedia: "a unit is the smallest testable part of an application" and logically such 'units' are smaller than most 'features'.

What I am saying is that unit testing is the extreme, and is rarely necessary - with the possible exception of super-critical software (real-time control systems where lives may be endangered, for example) or projects with no limits on budget and timeline.

For most software, from a practical point of view, testing features is all that is required. Testing units smaller than features won't hurt, and it might help, but the trade-off in productivity vs improvements in quality are debatable.

answered 2008-12-07T08:27:07.450

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