Unlock the Power of Unit Testing: A Beginner’s Guide to Quality Software Development
Tags: nunit, unittest, programming, testing
Published: 2023-01-30 18:15:08

![](https://cdn-images-1.medium.com/max/2048/1*ln5ivvzEaIHyRiYz6zgazA.png)

👋Greetings and welcome to in-depth manual on unit testing in software development 🎉 We’ll be diving deep into the world of unit testing in this article, learning what it is, why it’s crucial, and how it can help ensure the quality and dependability of your software.

Unit testing is a technique for checking that individual software parts function as intended. Before software is made available to the general public, it can be tested for dependability and quality.

Consider unit testing as a form of factory quality control. A product must pass thorough testing before it is released into the market. Any issues can be resolved before the product is delivered to the customer. Software development utilizes the same idea.

Unit testing makes it simpler and more affordable to make changes by assisting developers in identifying and fixing bugs early in the development process. It also acts as a backup plan for future modifications, giving programmers the assurance they need to add new features without affecting those already in place.

### Unit Testing In Details

The smallest testable component of an application, such as a function or method, is referred to as a unit in software development. The process of unit testing includes creating and running tests for these independent units. The tests examine the behavior of the unit being tested and confirm that it complies with the given requirements.

Every time the code is modified, unit tests are typically automated and run to make sure no new bugs or functional issues are introduced. The tests should run quickly, produce consistent, repeatable results, and be simple and quick to run.

Unit tests are a critical element of an **Agile software development process** because they can find issues early in the cycle, when fixing them is less expensive. By requiring developers to think critically about how their code should behave and how it will be used, writing and maintaining unit tests can also help improve the design and quality of the code.

### Why Do Developers Need Unit Tests?

* **Early bug detection: **Unit tests assist in the early detection of bugs, which makes their correction simpler and less expensive.

* **Faster and easier code refactoring: **When making changes to code, unit tests act as a safety channel, making refactoring or other changes simpler and less risky.

* **Improved code quality: **Writing unit tests helps developers to write cleaner, more maintainable code, which helps them think critically about the behavior of their code and can enhance code quality.

* **Better documentation: **Unit tests can act as a kind of code documentation, making it simpler for other developers to comprehend how the code operates and what it does.

* **Increased confidence in code: **Unit tests give programmers a high level of assurance that their code is functioning as intended, lowering the risk of bugs and other issues in production environments.

### Unit Testing Tips & Tricks

* **Write tests first: **Before writing any code, write some tests to help you think through the behavior of the code and make sure it can be tested.

* **Test both positive and negative scenarios:** Test both scenarios, including edge cases and error conditions, for a unit.

* **Keep tests simple and focused: **Tests should be straightforward and concentrated on a single functional component. Complex tests can be more challenging to maintain and less successful at finding bugs.

* **Avoid testing implementation details: **Tests should examine how the code behaves, not how it was implemented. Tests ought to pass even if the implementation is altered.

* **Automate tests: **Automate tests as much as you can to make it simpler to run tests frequently and make sure they are reliable and consistent.

* **Make tests run quickly: **Tests should run quickly so that developers can run them frequently and receive quick feedback on their code.

* **Isolate tests: **Test isolation is important to ensure that changes to one test do not have an impact on the outcomes of other tests.

* **Maintain tests: **As the code changes, keep the tests current. Also, make sure to delete tests that are no longer required.

* **Use appropriate testing frameworks**: Use testing frameworks that are well-suited for unit testing, such as **JUnit **for Java or **pytest **for Python, **NUnit **for .Net.

### Most Known Unit Test Frameworks

Here are some of the most popular unit testing frameworks:

    JUnit: A popular testing framework for Java applications.
    
    NUnit: A testing framework for .NET applications, including C#.
    
    xUnit: A testing framework for .NET applications, including C#.
    
    pytest: A testing framework for Python applications.
    
    RSpec: A testing framework for Ruby applications.
    
    PHPUnit: A testing framework for PHP applications.
    
    Mocha: A testing framework for JavaScript applications.

These are some of the best-known and most frequently used frameworks for unit testing. The programming language and application you are using will let you chose the testing framework you need.

Since we’ll use C# .Net Core as sample project in this article, let’s have a look at pros & cons of **NUnit **and **xUnit **testing frameworks 👇

### 💠NUnit

    Pros:
    
    Open source: NUnit is open source, so it is free to use and can be 
    easily modified and customized to meet the needs of your project.
    
    Large community: NUnit has a large community of users, so there is a lot 
    of help and support available, including forums, tutorials, and plugins.
    
    Extensive functionality: NUnit has extensive functionality, including 
    advanced features for testing, such as data-driven testing and code 
    generation.
    
    
    Cons:
    
    Steep learning curve: NUnit has a steep learning curve for new users, as 
    it has a lot of features and options.
    
    Integration with Visual Studio: Integration with Visual Studio can be 
    difficult, as NUnit is not built into Visual Studio and requires 
    additional setup.

### 💠xUnit

    Pros:
    
    Open source: xUnit is open source, so it is free to use and can be easily 
    modified and customized to meet the needs of your project.
    
    Clean and simple: xUnit has a clean and simple design, making it easy to 
    use and understand for new users.
    
    Extensive functionality: xUnit has a wide range of capabilities, including 
    sophisticated testing tools like data-driven testing and code generation.
    
    
    Cons:
    
    Steep learning curve: xUnit has a steep learning curve for new users, as 
    it has a lot of features and options.
    
    Integration with Visual Studio: Integration with Visual Studio can be 
    difficult, as xUnit is not built into Visual Studio and requires 
    additional setup.

As you can see; their pros & cons are nearly same, so it is up to you which one to go with when it comes to making a decision about NUnit and xUnit.

In this article, we’ll use NUnit in our sample project.

### Let’s create a sample Web API unit test with using **NUnit **from scratch for a .Net Core API Project

 1. Open Visual Studio and create a new **ASP.NET Core Web API **project.

![Screenshot from Visual Studio new project creation window](https://cdn-images-1.medium.com/max/2536/1*ZMZ8h3FBbjYl-bRPl5lI7Q.png)

2. In the Solution Explorer, right-click on the project and select “**Manage NuGet Packages**”.

![Screenshot from Visual Studio project context menu in Solution Explorer window](https://cdn-images-1.medium.com/max/2000/1*rc2vHSVJbeUKGpV_rU7d2A.png)

3. From the NuGet Package Manager, install following packages;

* [**Microsoft.NET.Test.Sdk](https://www.nuget.org/packages/Microsoft.NET.Test.SDK)**

* [**NUnit](https://www.nuget.org/packages/NUnit)**

* [**NUnit3TestAdapter](https://www.nuget.org/packages/NUnit3TestAdapter)**

![Screenshot from Visual Studio Nuget Package Manager window’s installed tab](https://cdn-images-1.medium.com/max/2788/1*p5ZDbiADj84qTX25C0CYww.png)

4. In your project, add a new controller and name it “**MediumSampleAPIController**”. With simple *Get()* method, we’ll just return a string from our controller.

![Screenshot from Visual Studio showing our new API controller “MediumSampleAPI” with it’s Get method codes](https://cdn-images-1.medium.com/max/3060/1*FCYDbujNwecXEkVL1ia5Pw.png)

5. Add a new class and name it as “**MediumSampleAPITests**” which will include our sample API controller’s tests.

![Screenshot from Visual Studio Solution Explorer showing new created class called “MediumSampleAPITests”](https://cdn-images-1.medium.com/max/2000/1*j9os27EAOF62KIJeyLVszA.png)

6. Let’s add our test method into “MediumSampleAPITests” class

`[TestFixture]
public class MediumSampleAPITests
{
	[Test]
	public async Task TestGetMethod()
	{
		// Arrange
		var controller = new MediumSampleAPIController();

		// Act
		var result = controller.Get();

		// Expected result string
		string expected = "Hello World, this is Medium article Sample API project.";

		// Assert
		Assert.IsNotNull(result);
		Assert.AreEqual(expected, result.Value);
	}
}`

7. Now if you right click to “MediumSampleAPITests” class and click on “Run Tests” you’ll see Visual Studio’s “Test Explorer” window appears and your test will be executed.

![Screenshot from Visual Studio Test Explorer](https://cdn-images-1.medium.com/max/3308/1*MtqhNZJBz8amA0Qwqz_hrQ.png)

❗ Also you can use Visual Studio’s debugger to debug your tests by just clicking “Debug Tests” button as well;

![Screen recording from debugging tests](https://cdn-images-1.medium.com/max/3344/1*8pZwUZ1EpoWk9dF03vocsA.gif)

👉And also if the “**expected**” does not meet with “**actual**” your test will be failed ❌

![Screenshot from failed test](https://cdn-images-1.medium.com/max/3330/1*FcnU2jtBEYcWSDyhKtlg2A.png)

This is a basic example of how to create an NUnit unit test for a simple API in a controller with C#. You can find more information and resources on the [NUnit websit](https://nunit.org/)e and in the [NUnit documentation](https://docs.nunit.org/).

### Let’s dive into our test code 👇

    [Test]
    public async Task TestGetMethod()
    {
        // Arrange
        var controller = new MediumSampleAPIController();
    
        // Act
        var result = controller.Get();
    
        // Expected result string
        string expected = "This is expected";
    
        // Assert
        Assert.IsNotNull(result);
        Assert.AreEqual(expected, result.Value);
    }

    [Test]
    The [Test] attribute is a marker for NUnit indicating that the 
    following method is a unit test.
    
    public async Task TestGetMethod()
    This line defines the method TestGetMethod as a public asynchronous task. 
    Asynchronous tasks are used in C# to perform work that may take a long 
    time to complete, without blocking the execution of the rest of the 
    program.
    
    // Arrange
    var controller = new MediumSampleAPIController();
    The Arrange section is used to prepare the objects and variables that 
    will be used in the test. Here, a new instance of the 
    MediumSampleAPIController class is created and assigned to the 
    controller variable.
    
    // Act
    var result = controller.Get();
    The Act section is where the actual work of the test is performed. 
    In this case, the Get method of the controller object is called and 
    the result is stored in the result variable.
    
    // Expected result string
    string expected = "This is expected";
    Here, a string variable named expected is declared and initialized with 
    the value "This is expected". This variable will be used to compare the 
    actual result of the test to what is expected.
    
    // Assert
    Assert.IsNotNull(result);
    Assert.AreEqual(expected, result.Value);
    The Assert section is where the test's results are verified. The first 
    line Assert.IsNotNull(result), checks that the result variable is not 
    null, indicating that the Get method returned a value. The second line, 
    Assert.AreEqual(expected, result.Value), compares the expected string to 
    the Value property of the result object, making sure that they are equal. 
    If they are equal, the test will pass. If not, the test will fail and an 
    error message will be generated indicating why the test failed.

### Common Assertion Methods in NUnit

    Assert.IsTrue(condition) - Verifies that the condition is true.
    
    Assert.IsFalse(condition) - Verifies that the condition is false.
    
    Assert.AreEqual(expected, actual) - Verifies that two values are equal.
    
    Assert.AreNotEqual(expected, actual) - Verifies that two values are not equal.
    
    Assert.IsNull(value) - Verifies that a value is null.
    
    Assert.IsNotNull(value) - Verifies that a value is not null.
    
    Assert.IsInstanceOf(expectedType, value) - Verifies that a value is of the 
    expected type.
    
    Assert.Throws(expectedExceptionType, delegate) - Verifies that a delegate 
    throws an exception of the specified type.
    
    Assert.That(expression, constraint) - Verifies that an expression matches 
    a specified constraint.
    
    CollectionAssert.AreEqual(expected, actual) - Verifies that two collections 
    contain the same elements in the same order.

Here are some examples of NUnit assertions 👇

**Example 1:** Asserting that a condition is true:

    int a = 5;
    int b = 3;
    Assert.IsTrue(a > b);

**Example 2: **Asserting that two values are equal:

    string expected = "Hello World";
    string actual = "Hello World";
    Assert.AreEqual(expected, actual);

**Example 3:** Asserting that a value is not null:

    object value = new object();
    Assert.IsNotNull(value);

**Example 4:** Asserting that a value is of the expected type:

    object value = "Hello World";
    Assert.IsInstanceOf(typeof(string), value);

**Example 5:** Asserting that a delegate throws an exception:

    int a = 0;
    int b = 0;
    Assert.Throws(typeof(DivideByZeroException), delegate { int c = a / b; });

**Example 6:** Asserting that an expression matches a constraint:

    int[] values = { 1, 2, 3, 4, 5 };
    Assert.That(values, Has.Length.EqualTo(5));

These are just a few types of assertions that NUnit supports. The [NUnit documentation](https://docs.nunit.org/) contains more details and examples.

Thank you for taking the time to read the article about Unit Testing. 🤗 I hope this article has helped you to understand Unit Test, it’s benefits, well-known unit test frameworks and NUnit with .NET Core Web API in real life scanario.

Please feel free to ask any more questions if you have any 👏

### Fun Fact 😄

*Why do software engineers love writing unit tests?
***Because it gives them a chance to catch their own mistakes before their boss does! 😂**