XCTestCase

Any class that inherits XCTestCase is automatically retained along with its test methods.

However, when a class inherits XCTestCase indirectly via another class, e.g., UnitTestCase, and that class resides in a target that isn’t scanned by Periphery, you need to use the --external-test-case-classes UnitTestCase option to instruct Periphery to treat UnitTestCase as an XCTestCase subclass.