By construction, functional code and test code are tested one against the other. One problem remains: the case of common mode bugs, when a bug in functional code is hidden by a bug in test code. TDD is not immune to this effect. This is why testing is usually performed at multiple levels by different people in order to decrease this probability.

Aug 29, 2011 · Finding hard to test code and making it easier to test will, well, make it easier for you to write test cases. Also, catching defects early will add value to your entire quality assurance practices (which include testing). From here, getting familiar with unit testing tools and mocking tools will make it easier for you to implement your testing.

Oct 14, 2015 · If you write a test that passes, then you have no extra code to write, effectively spending more time to write test than code. (This does not account for code refactoring, which aims at spending less time writing subsequent code. It is balanced by test refactoring, which aims at spending less time writing subsequent tests.)

Jun 13, 2016 · Write a function, write a test, test it done. Change something - get if your previous test covers it, if yes you are done if not write another small test and test. Here is a bit more information if you would like to find out some more!

The same goes for unit tests - If a test fails it indicates something is wrong. It might be the production code, but it might aswell be the test code! This last part if important. Note that your type (1) bugs cannot be found by unit tests. To avoid this types of bugs you need other tools.

More specific tests mean more test code. More generic production code means less code, so test/code ratios should rise as the code evolves. But wait, that's not good either. In some particular cases, for example when you define a certain algorithm, you may have only 6-10 lines of code containing a couple of "if"s, a while and maybe 2-3 recursions.

Generally speaking, these code interact with main logic directly and if the test code is defective, the business logic is affected. One example could be that we have some test code around date/time logic so that if the testers make server and client time different, this code could help them to perform some tests.

May 18, 2011 · Minimize Test-Code Distance: There should be a clear and short path between the test and the code that implements it. Long distances create unnecessarily long feedback loops. Test One Thing At A Time: Unit tests should only test one thing. If you need to test another thing, write another test.

Bigger tests than code? It depends. Sometimes the test will be more complex. Sometimes the code will be more complex. Refactoring to Simplify Code and Test Cases. It may be worth considering some simplifications and refactoring if things are getting exponential on you. I have worked with several maintenance projects that were littered with God ...

Nov 21, 2011 · Code that is hard to test and stable Category 1 is the obvious place to start, where you can get much benefit with relatively little work. Category 2 allows you to quickly improve your coverage statistic (good for morale) and get more experience with the codebase, while category 3 is more (often frustrating) work but also yields more benefit.