How to use Assert.Throws to assert the type of the exception in C#?

How to use Assert.Throws to assert the type of the exception in C#?

In C#, you can use the Assert.Throws method provided by the NUnit testing framework to assert that a specific type of exception is thrown by a method. Here's an example code snippet that demonstrates how to use Assert.Throws to assert the type of the exception:

 using NUnit.Framework; [TestFixture] public class MyTestClass { [Test] public void MyTestMethod() { // Arrange MyClass myClass = new MyClass(); // Act and Assert Assert.Throws<ArgumentNullException>(() => myClass.MyMethod(null)); } } public class MyClass { public void MyMethod(object obj) { if (obj == null) { throw new ArgumentNullException(nameof(obj)); } // ... } }

In this example, the Assert.Throws method is used to assert that the MyMethod method of the MyClass class throws an ArgumentNullException when it is called with a null argument. The lambda expression passed to Assert.Throws specifies the method call that is expected to throw the exception.

If the method call does not throw an exception of the specified type, the test will fail with a message that indicates that the expected exception was not thrown. If the method call throws an exception of a different type, the test will also fail.

Note that you need to add a reference to the NUnit.Framework assembly and include the using NUnit.Framework; directive in your code to use the Assert.Throws method.

Examples

  1. "C# Assert.Throws Example"

    • Description: Find an example demonstrating the usage of Assert.Throws to validate the occurrence and type of exceptions in C# unit tests.
    • Code Implementation:
      Assert.Throws<InvalidOperationException>(() => { /* Code that should throw InvalidOperationException */ });

  2. "Assert.Throws Specific Exception Type C#"

    • Description: Learn how to use Assert.Throws to specifically assert the occurrence of a particular exception type in C# unit testing.
    • Code Implementation:
      Assert.Throws<ArgumentNullException>(() => { /* Code that should throw ArgumentNullException */ });

  3. "C# MSTest Assert.Throws Example"

    • Description: Explore examples of using Assert.Throws in MSTest framework for C# to verify expected exceptions in unit tests.
    • Code Implementation:
      Microsoft.VisualStudio.TestTools.UnitTesting.Assert.ThrowsException<InvalidOperationException>(() => { /* Code that should throw InvalidOperationException */ });

  4. "XUnit Assert.ThrowsAsync Example"

    • Description: Understand how to use Assert.ThrowsAsync in xUnit framework for C# to handle asynchronous methods and assert exception types.
    • Code Implementation:
      await Assert.ThrowsAsync<DivideByZeroException>(() => DivideAsync(1, 0));

  5. "C# NUnit Assert.Throws Custom Exception"

    • Description: Find examples of using Assert.Throws in NUnit framework for C# to check for custom exception types in unit tests.
    • Code Implementation:
      Assert.Throws<CustomException>(() => { /* Code that should throw CustomException */ });

  6. "Assert.Throws Specific Exception Message C#"

    • Description: Learn how to assert both the type and message of an exception using Assert.Throws in C# unit tests.
    • Code Implementation:
      Assert.Throws<DivideByZeroException>(() => Divide(1, 0), "Cannot divide by zero.");

  7. "Assert.Throws vs Assert.DoesNotThrow C#"

    • Description: Understand the differences between Assert.Throws and Assert.DoesNotThrow in C# unit testing and when to use each.
    • Code Implementation:
      Assert.Throws<InvalidOperationException>(() => { /* Code that should throw InvalidOperationException */ }); Assert.DoesNotThrow(() => { /* Code that should not throw any exception */ });

  8. "C# Assert.Throws Generic Exception"

    • Description: Explore how to use Assert.Throws to handle scenarios where the expected exception type is a generic exception in C#.
    • Code Implementation:
      Assert.Throws<SomeGenericException<int>>(() => { /* Code that should throw SomeGenericException<int> */ });

  9. "Assert.Throws for Exception in async C# code"

    • Description: Learn to use Assert.ThrowsAsync in C# unit tests for asserting exception types in asynchronous code.
    • Code Implementation:
      await Assert.ThrowsAsync<InvalidOperationException>(async () => await SomeAsyncMethod());

  10. "C# xUnit Assert.ThrowsAny Example"

    • Description: Explore the usage of Assert.ThrowsAny in xUnit framework for C# to assert the occurrence of any exception type.
    • Code Implementation:
      Assert.ThrowsAny<Exception>(() => { /* Code that should throw any exception */ });

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