Unit Tests

Unit testing is a great idea. It provides for code coverage, is a resource for documentation, and it provides a vehicle for good design.

Naming your tests

The name of the test should tell you what the test is doing without you having to read every line of code to figure it out. It should explain the prerequisites. It should explain what behavior we expect from the function under test. It should help you frame your mind so that when a test fails you can more easily figure out what broke.

The name of your test should consist of three parts:

The name of the method being tested.
The scenario under which it's being tested.
The expected behavior when the scenario is invoked.

MethodUnderTest_Scenario_Behavior

Samples:

Add_SingleNumber_ReturnsSameNumber
Add_MultipleNumbers_ReturnsSumOfNumbers
Add_MaximumSumResult_ThrowsOverflowException

Arranging your tests

The AAA (Arrange, Act, Assert) pattern is a common way of writing unit tests for a method under test.

The Arrange section of a unit test method initializes objects and sets the value of the data that is passed to the method under test.

The Act section invokes the method under test with the arranged parameters.

The Assert section verifies that the action of the method under test behaves as expected.

Following this pattern does make the code quite well structured and easy to understand. In general lines, it would look like this:

// arrange
var repository = Substitute.For<IClientRepository>();
var client = new Client(repository);

// act
client.Save();

// assert
mock.Received.SomeMethod();

Comments // can be skipped.

Structure

Basic

Sources:

/XToolkit.Common
  /Extensions
    StringExtensions.cs

Tests:

/XToolkit.Common.Tests
  /Extensions
    /StringExtensionsTests
      StringExtensionsTests.cs
      ... <-- any related classes

Advanced