How to write Unit Tests in .net

Unit tests are automated tests that verify the behavior code like methods and functions. Writing unit tests is crucial to clean coding, as they help ensure your code works as intended and catches bugs early in the development process. I can share some tips for writing effective unit tests:

Write tests for all public methods

Every public method in your code should have a corresponding unit test. This helps ensure that your code behaves correctly and catches any unexpected behavior early.

public class Calculator {

    public int Add(int a, int b) {
        return a + b;
    }
}

[TestClass]
public class CalculatorTests {
    [TestMethod]
    public void Add_ShouldReturnCorrectSum() {
        // Arrange
        Calculator calculator = new Calculator();
        int a = 1;
        int b = 2;
        // Act
        int result = calculator.Add(a, b);
        // Assert
        Assert.AreEqual(3, result);
    }
}

Test boundary conditions 

Make sure to test boundary conditions, such as null inputs or extreme values, to catch any edge cases that may cause problems.

public class Validator {

    public bool IsPositive(int number) {
        return number > 0;
    }
}

[TestClass]
public class ValidatorTests {
    [TestMethod]
    public void IsPositive_ShouldReturnFalseForZero() {
            // Arrange
            Validator validator = new Validator();
            // Act
            bool result = validator.IsPositive(0);
            // Assert
            Assert.IsFalse(result);
        }
        [TestMethod]
    public void IsPositive_ShouldReturnTrueForPositiveNumber() {
        // Arrange
        Validator validator = new Validator();
        // Act
        bool result = validator.IsPositive(3);
        // Assert
        Assert.IsTrue(result);
    }
}

Use a consistent naming convention :

Use a consistent naming convention for your tests, such as [MethodName]_Should[ExpectedBehavior], to make it clear what the test is testing. 

Keep your tests independent :

Make sure that your tests are independent of each other and don't rely on external state. This helps ensure that your tests are reliable and reproducible. 

Run your tests frequently:

Ideally after every code change we need to run unit tests to catch bugs early in the development process.