86 lines
3.4 KiB
Markdown
86 lines
3.4 KiB
Markdown
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# 4\. Custom comparison
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## Learning objectives
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This exercise will cover the custom equality comparers included in Unity Test Framework, such as `Vector3EqualityComparer`. These are used to assert on e.g. Vectors.
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## Intro and motivation
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We have extended the assertion capabilities of NUnit with some custom comparisons for Unity-specific objects. A good example of this is the ability to compare two `Vector3` objects.
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An example of its use is:
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```
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actual = new Vector3(0.01f, 0.01f, 0f);
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expected = new Vector3(0.01f, 0.01f, 0f);
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Assert.That(actual, Is.EqualTo(expected).Using(Vector3EqualityComparer.Instance));
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```
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This allows us to verify that the two vectors are identical within a given tolerence. By default the tolerance is 0.0001f. The tolerance can be changed by providing a new `Vector3EqualityComparer`, instead of using the default in .instance. For example you can up the tolerance to 0.01f with the following:
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```
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Assert.That(actual, Is.EqualTo(expected).Using(new Vector3EqualityComparer(0.01f));
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```
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For a list of all available custom comparers, see [Custom equality comparers](https://docs.unity3d.com/Packages/com.unity.test-framework@1.1/manual/reference-custom-equality-comparers.html).
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## Exercise
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Similar to the project for exercise 3, the [sample](./welcome.md#import-samples) `4_CustomComparison` contains a `ValueOutputter` class.
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Verify that the `ValueOutputter` returns the correct values from its methods:
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* `GetVector3()` should return a `Vector3` that is roughly equal to (10.333, 3, 9.666).
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* `GetFloat()` should return a `float` that is roughly 19.333. This is the same as previous exercise, but you can try to solve this with a `FloatEqualityComparer`.
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* `GetQuaternion` should return a [Quaternion](https://docs.unity3d.com/ScriptReference/Quaternion.html) object that should be roughly equal to (10f, 0f, 7.33333f, 0f).
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## Hints
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* For some of the exercises, you might need to provide a custom error tolerance to the comparer.
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* If the comparison fails, the comparers give a message about the actual and expected value, just like a normal assertion. However, because `ToString` on `Vector3` rounds the value off before displaying it, the two values in the string message might be equal, even when their `Vector3` values are not.
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## Solution
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The full solution is available in the sample `4_CustomComparison_Solution`.
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```
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[Test]
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public void Vector3ReturnsCorrectValue()
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{
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var valueOutputterUnderTest = new ValueOutputter();
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var vector3 = valueOutputterUnderTest.GetVector3();
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var expected = new Vector3(10.333f, 3f, 9.666f);
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Assert.That(vector3, Is.EqualTo(expected).Using(new Vector3EqualityComparer(0.001f)));
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}
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[Test]
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public void FloatReturnsCorrectValue()
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{
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var valueOutputterUnderTest = new ValueOutputter();
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var actualFloat = valueOutputterUnderTest.GetFloat();
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Assert.That(actualFloat, Is.EqualTo(19.333f).Using(new FloatEqualityComparer(0.001f)));
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}
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[Test]
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public void QuaternionReturnsCorrectValue()
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{
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var valueOutputterUnderTest = new ValueOutputter();
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var actualValue = valueOutputterUnderTest.GetQuaternion();
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var expectedValue = new Quaternion(10f, 0f, 7.33333f, 0f);
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Assert.That(actualValue, Is.EqualTo(expectedValue).Using(new QuaternionEqualityComparer(0.001f)));
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}
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```
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## Further reading and resources
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[Custom equality comparers](https://docs.unity3d.com/Packages/com.unity.test-framework@1.1/manual/reference-custom-equality-comparers.html)
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