# 3. Semantic test assertion

> Use Assert.That to test whether conditions are true.

## Learning objectives

This exercise introduces the `Assert.That` and related classes.

## Intro and motivation

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.

Here are some examples on how to use the semantic assertion classes:

```lang-cs
Assert.That(myValue, Is.GreaterThan(20));
Assert.That(str, Does.Contain("a string").And.Contain("something else"));
```

Here we check that the variable `myValue` is greater than 20 and then that the string `str` contains both "a string" and "something else".

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.

## Exercise

In the `3_SemanticTestAssertion` [sample](/engine/6000.3/manual/scripting/test-framework-introduction/overview/general-introduction.md#import-samples), there is a class called `ValueOutputter`, which returns values of different types.

Write tests that assert on the different outputs. It should be verified that:

* `GetInt()` returns 11.
* `GetString()` returns a string that contains the words `string` and `asserted`.
* `GetFloat()` returns a value that is around 19.33.

## Hints

* 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.

## Solution

A full solution to the exercise is available in the sample `3_SemanticTestAssertion_Solution`.

```lang-cs
internal class ValueOutputterTests
{
 [Test]
 public void GivesExpectedInt()
 {
  var outputterUnderTest = new ValueOutputter();

  var number = outputterUnderTest.GetInt();
  
  Assert.That(number, Is.EqualTo(11));
 }
 
 [Test]
 public void GivesExpectedString()
 {
  var outputterUnderTest = new ValueOutputter();

  var str = outputterUnderTest.GetString();
  
  Assert.That(str, Does.Contain("string").And.Contain("asserted"));
 }
 
 [Test]
 public void GivesExpectedFloat()
 {
  var outputterUnderTest = new ValueOutputter();

  var number = outputterUnderTest.GetFloat();
  
  Assert.That(number, Is.GreaterThan(19.33f).And.LessThan(19.34f));
 }
}
```

## Additional resources

* [Constraint-Based Assert Model](https://nunit.org/docs/2.4/constraintModel.html)