Unit testing your code

Unit tests are blocks of code that verify the correct output of one small part of your code (a unit) at a time, such as an individual function or class. D has a built-in support for basic unit testing. Here, we'll see what we can do with it.

How to do it…

Perform the following steps:

1. Add unittest {} blocks to your modules, under your functions and inside your classes.

2. Put any imports needed by the test inside the unittest block.

3. You should write helper function and class definitions inside the unittest block.

4. Write assertions to perform your tests.

5. Use std.exception for additional helper functions.

6. Compile with dmd –unittest yourfiles.d.

7. Run the program.

   Tip

   Design your classes with dependency injection for easier mocking of tests. This is when instead of constructing child objects yourself, you accept them as arguments to the constructor. The unit test may then pass a dummy object to the class instead of, for example, a live network connection to test the code.

   Consider the following...