Enabling code coverage

Measuring the code coverage of our tests gives us a feeling of completeness about our test suite. When following the TDD workflow, as we don't write any code without a failing test, the code coverage of our project should be very high. We don't expect it to be 100%, meaning that all the code paths are executed in the tests because the static analyzer forces us to write code that we don't expect to be executed. For example, in the code we wrote, we often used guard to make sure that the value we wanted to access was not nil. We could have written tests for a case where the value was nil. But in my opinion, these tests give no additional value.

Nevertheless, we will examine the parts of the project without code coverage and discuss whether we need to add tests to cover them.

Code coverage in Xcode

Xcode has added native support for the measurement of code coverage of tests with version 7. To enable it, select Edit Scheme... in the Scheme selector in Xcode:

In the following...