Testing the Repository

The objective of a test suite is to completely test the functionality of the main code, including all code paths. Often, this gets measured in the form of “test coverage”, where we confirm:

• Whether all lines of code were executed
• Whether both the true and false branches of an if condition were taken
• Whether a loop was executed 0, 1, and N times
• And so on

This project does not have 100% test coverage. Few projects presented in books have 100% test coverage.

This tutorial extends our test coverage a bit, by testing ToDoRepository and our Room code. To do that, though, we will switch to writing instrumented tests. Room is designed to use Android’s SQLite by default, and so it is much easier to test this stuff when we run our tests on Android, rather than on our development machine.

Testing in instrumented tests is a lot like unit testing:

• We write JUnit tests with @Test functions and so on
• We use assertions to determine whether our tests succeed or fail
• We can run the tests from Android Studio to see whether they work

On the other hand, there are substantial differences as well:

• The tests will run in an Android environment, on our chosen device or emulator
• The tests will be subject to some Android limitations, just as the regular Kotlin code that we might use on a server will not necessarily work in Android

This is a continuation of the work we did in the previous tutorial. The book’s GitLab repository contains the results of the previous tutorial as well as the results of completing the work in this tutorial.

Step #1: Renaming Our Instrumented Test

The existing instrumented test class, inside the androidTest source set, is ExampleInstrumentedTest. This is not a very useful name. Since we will be testing some of the functionality from ToDoRepository, we should rename it to ToDoRepositoryTest. And, since ToDoRepository is in the repo sub-package, we should have the test class mimic that.

In the androidTest source set, right click over the com.commonsware.todo.repo package and choose “New” > “Package” from the context menu. Fill in com.commonsware.todo.repo for the name, then click “OK” to make this sub-package.

Then, drag-and-drop the ExampleInstrumentedTest into this new repo sub-package. The default values in the “Move” dialog should be fine, so just click “Refactor” to make the move.

Finally, right-click over the ExampleInstrumentedTest class and choose “Refactor” > “Rename” from the context menu. Fill in ToDoRepositoryTest as the replacement name, and click “Refactor” to make the change.