# Replace JUnit Expected Annotation Property with assertThrows
# Description
Using the expected (opens new window) annotation property for testing the thrown exceptions is rather misleading.
Often it becomes unclear which part of the test code is responsible for throwing the exception.
This rule aims to overcome this problem by replacing the expected annotation property with assertThrows (opens new window) introduced in JUnit 4.13.
Requirements
This rule requires one of the following libraries to be present:
- junit:junit:4.13
- org.junit.jupiter:junit-jupiter-api:5.0.0
# Benefits
Improves the tests readability. Helps migrating to JUnit 5.
# Tags
# Code Changes
# Removing expected Property
Pre
@Test(expected = PersistenceException.class)
public void invalidRepo_shouldThrowPersistenceException() throws PersistenceException {
User user = new User("10", "John", "wolf");
invalidUserRepository.save(user);
}
Post
@Test
public void invalidRepo_shouldThrowPersistenceException() {
User user = new User("10", "John", "wolf");
assertThrows(PersistenceException.class, () -> invalidUserRepository.save(user));
}
# Multiple Annotation Properties
Pre
@Test(expected = PersistenceException.class, timeout = 500L)
public void timeoutInvalidRepo_shouldThrowPersistenceException() throws PersistenceException {
User user = new User("10", "John", "wolf");
invalidUserRepository.save(user);
}
Post
@Test(timeout = 500L)
public void timeoutInvalidRepo_shouldThrowPersistenceException() {
User user = new User("10", "John", "wolf");
assertThrows(PersistenceException.class, () -> invalidUserRepository.save(user));
}
# Limitations
- Expected RuntimeExceptions (opens new window) are not supported unless it can be explicitly inferred that only the last statements throws the expected exception.
@Test(expected=NullPointerException.class)
public void expectingRuntimeException() {
User user = userRepository.findById("10");
user.setName("John")
userRepository.save(user);
throwRuntimeException();
}
🛠️ Auto-refactor Available
You can auto-refactor this with jSparrow.
Drop this button to your Eclipse IDE workspace to install jSparrow for free:
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