78 lines
2.4 KiB
Markdown
78 lines
2.4 KiB
Markdown
# 3\. Semantic test assertion
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## Learning objectives
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This exercise introduces the `Assert.That` and related classes.
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## Intro and motivation
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The NUnit test framework and the Unity Test Framework have a series of classes for asserting objects in a way that is closer to natural language. This makes the statements easily readable.
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Here are some examples on how to use the semantic assertion classes:
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```
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Assert.That(myValue, Is.GreaterThan(20));
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Assert.That(str, Does.Contain("a string").And.Contain("something else"));
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```
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Here we check that the variable `myValue` is greater than 20 and then that the string `str` contains both "a string" and "something else".
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The semantic assertion is also known as [Constraint Model](https://docs.nunit.org/articles/nunit/writing-tests/assertions/assertion-models/constraint.html). Other than `It` and `Does` there are multiple other keywords that can be used.
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## Exercise
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In the `3_SemanticTestAssertion` [sample](./welcome.md#import-samples), there is a class called `ValueOutputter`, which returns values of different types.
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Write tests that assert on the different outputs. It should be verified that:
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* `GetInt()` returns 11.
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* `GetString()` returns a string that contains the words `string` and `asserted`.
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* `GetFloat()` returns a value that is around 19.33.
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## Hints
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* Asserting on the float might require a check for the value being greater than 19.33 and less than 19.34, as the output is not rational.
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## Solution
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A full solution to the exercise is available in the sample `3_SemanticTestAssertion_Solution`.
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```
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internal class ValueOutputterTests
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{
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[Test]
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public void GivesExpectedInt()
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{
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var outputterUnderTest = new ValueOutputter();
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var number = outputterUnderTest.GetInt();
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Assert.That(number, Is.EqualTo(11));
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}
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[Test]
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public void GivesExpectedString()
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{
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var outputterUnderTest = new ValueOutputter();
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var str = outputterUnderTest.GetString();
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Assert.That(str, Does.Contain("string").And.Contain("asserted"));
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}
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[Test]
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public void GivesExpectedFloat()
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{
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var outputterUnderTest = new ValueOutputter();
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var number = outputterUnderTest.GetFloat();
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Assert.That(number, Is.GreaterThan(19.33f).And.LessThan(19.34f));
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}
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}
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```
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## Further reading and resources
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[NUnit 2 documentation for the constraint model](https://nunit.org/docs/2.4/constraintModel.html)
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