Example of JUnit 5 – Expected Exception
Now we will execute this by using a basic example for a better understanding of the concept. Now we will take one Java class that is MyClass, and after that we will take one more Java class for Testing which is MyClassTest.
MyClass.java:
Java
public class MyClass { public void throwException() throws MyException { throw new MyException("This is Custom exception message"); } } |
In this above code, we have created one method that is throwException() which is throws an exception type MyException. In that method we have given test message as This is Custom exception message.
MyClassTest.java:
Now we will implement the testing class. The class name is MyClassTest which is used for testing the exceptions of MyClass.
Java
import org.junit.jupiter.api.Test; import static org.junit.jupiter.api.Assertions.assertThrows; public class ExampleTest { @Test public void testException() { MyClass myClass = new MyClass(); MyException exception = assertThrows(MyException.class, () -> { myClass.throwException(); }); assertEquals("This is Custom exception message", exception.getMessage()); } } |
In above example we have created object for MyClass after that we have uses assertThrows() method for checking excepted exception is came or not. And the assertEquals() is check the exception is equals with given exception and result exception. If both are same, then the test case will get passed otherwise it will not get passed.
Advantages of Expected Exception in JUnit 5
- Clarity and Readability
- Explicit Exception Type
- Capturing Thrown Exception
- Improved Failure Messages
- Integration with IDEs
- Consistency Across Test Code
- Compatibility with JUnit 5 Features
JUnit 5 – Expected Exception
In JUnit 5, Exception handling is changed compared to exception handling in JUnit 4. JUnit 5 provides the assertThrows() method for that particular exception thrown during execution of the Testing of an application. This assertThrows is available in org.junit.jupiter.api.Assertions class. Mostly this assertThrows() is used for testing expected exceptions.
Prerequisites
- Basic knowledge on exception handling
- Basic knowledge on testing
- Basic knowledge on JUnit 5 testing framework
- Must know information about Annotations in JUnit 5
Syntax of JUnit 5 Expected Exception
static <T extends Throwable> T assertThrows(Class<T> expectedType, Executable executable)
Parameters:
- exceptedType: The excepted type of the exception
- executable: The block of code that is expected to throw an exception.
Returns:
The exception was thrown during the execution of a given block of code in the class.