Step #5: Running the Stub Unit Test
You have a variety of ways to run the unit test. The simplest ones come from “run” icons in the gutter of the editor:
Functions that implement tests will have the @Test
annotation. Clicking the run icon next to a test function will run just that test function. Clicking the run icon next to a class will run all of the test functions in that class.
If you click the run icon next to SingleModelMotorTest
, that class’ test functions will be run, and the “Run” tool window will open in Android Studio to show you the results:
Our test function uses an assertEquals()
method supplied by JUnit. assertEquals()
compares two values and fails the test if they are not equal.
Not surprisingly, 2 + 2 does indeed equal 4.
(if you were surprised by this, once again… surprise!)
The test output shows passing tests with a green checkmark, so we can see that our test passed. Also, at this point, the run icons in the editor become “run again” icons, with the green check-circle indicating that the previous test passed:
If you change the assertEquals()
call to be assertEquals(5, 2 + 2)
and run the test again, you will see that it fails:
The yellow icon indicates that the test failed due to a failed assertion.
If you change the assertEquals()
call to be assertEquals(4, 2 / 0)
and run the test again, you will see that the test fails again. This time, though, the test output uses a red icon, to indicate that our test crashed:
Usually, after a test failure, our editor icons turn red, indicating that the previous run of the test failed:
As we add more test functions, you may get a mix of results, with some tests succeeding and some tests failing. The test class is only considered to have succeeded if all of its test functions succeed.
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