How Can JUnit 5\'s `assertThrows()` Simplify Exception Testing?

Enhanced Exception Assertions in JUnit 5

While @Rule was previously employed to verify exception handling in JUnit 5, it posed limitations when testing multiple exceptions within a single test. To streamline this process and gain additional flexibility, JUnit 5 introduced assertThrows().

преимущества использования assertThrows()

• Permits testing of multiple exceptions within a single test
• Embraces the power of lambda expressions in Java 8
• Represents the recommended approach for exception testing in JUnit

Использование assertThrows()

The syntax of assertThrows() is concise and intuitive:

assertThrows(expectedExceptionClass, supplier, message)

• expectedExceptionClass: Specifies the expected exception type
• supplier: A lambda expression that invokes the code anticipated to throw an exception
• message: An optional message to be displayed if the exception is not thrown

Пример использования

import static org.junit.jupiter.api.Assertions.assertThrows;

@Test
void exceptionTesting() {
    MyException thrown = assertThrows(
           MyException.class,
           () -> myObject.doThing(),
           "Expected doThing() to throw, but it didn't"
    );

    assertTrue(thrown.getMessage().contains("Stuff"));
}

By leveraging assertThrows(), you can now efficiently test for exceptions in JUnit 5, ensuring robust and thorough testing of your code.

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