9. Using the UnityTest Attribute
Learning objectives
This section will introduce you to the custom [UnityTest] Attribute, which allows for creating tests that run over multiple frames.
Intro and motivation
An important extension to the Nunit framework that we've made is introducing the [UnityTest] attribute. The attribute allows for creating tests that can yield and resume running after a certain condition. Therefore the test must have the return type of IEnumerator. You can then yield back a yield instruction or null, like so:
[UnityTest]
public IEnumerator MyTest()
{
DoSomething();
// Skip 1 frame.
yield return null;
DoSomethingElse();
}
In the snippet above we call the DoSomething method, then skip one frame before calling the DoSomethingElse method.
For more information on the yield keyword in C#, see the Microsoft documentation.
Exercise
In the sample 9_UnityTestAttribute you will find a Play Mode test assembly set up with one Play Mode test in it. The PlayMode test does not have a body yet, but there is a function called PrepareCube() which will set up a cube with some physics applied.
The task is to initialize the cube and then verify that it has moved after one frame has passed.
Solution
The full solution is available in the 9_UnityTestAttribute_Solution sample.
[UnityTest]
public IEnumerator CubeMovesDown()
{
var cubeUnderTest = PrepareCube();
var initialPosition = cubeUnderTest.transform.position;
yield return null;
Assert.That(cubeUnderTest.transform.position, Is.Not.EqualTo(initialPosition));
}