Your test should never be more than 10 lines of code

Here is one controversial commandment that always takes my students aback when I'm teaching them test-driven development. In F#, this is not a hard requirement and in C# it only brings a healthy restriction on the length of a test.

Because the length of a test is directly proportional with how readable this test is. A longer test will be less readable, and the longer it is the harder it will be to maintain. Instead, I propose that we should have as short tests as possible. The optimal length of a test would be three lines of code. We have the triple A syntax pattern as follows:

• Arrange

• Act

• Assert

Sometimes, you need a few more lines of arrange, in order to set up the prerequisites for the test to run. Assert might need an extra line to help extract the result we got from running the test.

The act section of the test should always be only one line of code. This is important to keep the test cohesive. If the act only consists of one line of code...