org.springframework.test
Class AssertThrows

java.lang.Object
  org.springframework.test.AssertThrows

public abstract class AssertThrows
extends Object

Simple method object encapsulation of the 'test-for-Exception' scenario (for JUnit).

Used like so:

 // the class under test
 public class Foo {
    public void someBusinessLogic(String name) {
        if (name == null) {
            throw new IllegalArgumentException("The 'name' argument is required");
        }
        // rest of business logic here...
    }
 }

The test for the above bad argument path can be expressed using the AssertThrows class like so:

 public class FooTest {
    public void testSomeBusinessLogicBadArgumentPath() {
        new AssertThrows(IllegalArgumentException.class) {
            public void test() {
                new Foo().someBusinessLogic(null);
            }
        }.runTest();
    }
 }

This will result in the test passing if the Foo.someBusinessLogic(..) method threw an IllegalArgumentException; if it did not, the test would fail with the following message:

 "Must have thrown a [class java.lang.IllegalArgumentException]"

If the wrong type of Exception was thrown, the test will also fail, this time with a message similar to the following:

 "junit.framework.AssertionFailedError: Was expecting a [class java.lang.UnsupportedOperationException] to be thrown, but instead a [class java.lang.IllegalArgumentException] was thrown"

The test for the correct Exception respects polymorphism, so you can test that any old Exception is thrown like so:

 public class FooTest {
    public void testSomeBusinessLogicBadArgumentPath() {
        // any Exception will do...
        new AssertThrows(Exception.class) {
            public void test() {
                new Foo().someBusinessLogic(null);
            }
        }.runTest();
    }
 }

You might want to compare this class with the ExceptionTestCase class.

Note: This class requires JDK 1.4 or higher.

Since:

2.0

Author:

Rick Evans, Juergen Hoeller

Constructor Summary

AssertThrows(Class expectedException)
Create a new instance of the AssertThrows class.

AssertThrows(Class expectedException, String failureMessage)
Create a new instance of the AssertThrows class.

Method Summary

protected void	checkExceptionExpectations(Exception actualException) Does the donkey work of checking (verifying) that the Exception that was thrown in the body of a test is an instance of the getExpectedException() class (or an instance of a subclass).
protected String	createMessageForNoExceptionThrown() Creates the failure message used if the test fails (i.e. the expected exception is not thrown in the body of the test).
protected String	createMessageForWrongThrownExceptionType(Exception actualException) Creates the failure message used if the wrong type of Exception is thrown in the body of the test.
protected void	doFail() Template method called when the test fails; i.e. the expected Exception is not thrown.
Exception	getActualException() Expose the actual exception thrown from test(), if any.
protected Class	getExpectedException() Return the Exception expected to be thrown during the execution of the surrounding test.
protected String	getFailureMessage() Return the extra, contextual failure message that will be included in the failure text if the text fails.
void	runTest() The main template method that drives the running of the test logic and the checking of the resulting (expected) Exception.
void	setFailureMessage(String failureMessage) Set the extra, contextual failure message that will be included in the failure text if the text fails.
abstract void	test() Subclass must override this abstract method and provide the test logic.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

AssertThrows

public AssertThrows(Class expectedException)

Create a new instance of the AssertThrows class.

Parameters:

expectedException - the Exception expected to be thrown during the execution of the surrounding test

Throws:

IllegalArgumentException - if the supplied expectedException is null; or if said argument is not an Exception-derived class

AssertThrows

public AssertThrows(Class expectedException,
                    String failureMessage)

Create a new instance of the AssertThrows class.

Parameters:

expectedException - the Exception expected to be thrown during the execution of the surrounding test

failureMessage - the extra, contextual failure message that will be included in the failure text if the text fails (can be null)

Throws:

IllegalArgumentException - if the supplied expectedException is null; or if said argument is not an Exception-derived class

Method Detail

getExpectedException

protected Class getExpectedException()

Return the Exception expected to be thrown during the execution of the surrounding test.

setFailureMessage

public void setFailureMessage(String failureMessage)

Set the extra, contextual failure message that will be included in the failure text if the text fails.

getFailureMessage

protected String getFailureMessage()

Return the extra, contextual failure message that will be included in the failure text if the text fails.

test

public abstract void test()
                   throws Exception

Subclass must override this abstract method and provide the test logic.

Throws:

Exception - if an error occurs during the execution of the aformentioned test logic

runTest

public void runTest()

The main template method that drives the running of the test logic and the checking of the resulting (expected) Exception.

See Also:

test(), doFail(), checkExceptionExpectations(Exception)

doFail

protected void doFail()

Template method called when the test fails; i.e. the expected Exception is not thrown.

The default implementation simply fails the test via a call to Assert.fail(String).

If you want to customise the failure message, consider overriding createMessageForNoExceptionThrown(), and / or supplying an extra, contextual failure message via the appropriate constructor overload.

See Also:

getFailureMessage()

createMessageForNoExceptionThrown

protected String createMessageForNoExceptionThrown()

Creates the failure message used if the test fails (i.e. the expected exception is not thrown in the body of the test).

Returns:

the failure message used if the test fails

See Also:

getFailureMessage()

checkExceptionExpectations

protected void checkExceptionExpectations(Exception actualException)

Does the donkey work of checking (verifying) that the Exception that was thrown in the body of a test is an instance of the getExpectedException() class (or an instance of a subclass).

If you want to customise the failure message, consider overriding createMessageForWrongThrownExceptionType(Exception).

Parameters:

actualException - the Exception that has been thrown in the body of a test method (will never be null)

createMessageForWrongThrownExceptionType

protected String createMessageForWrongThrownExceptionType(Exception actualException)

Creates the failure message used if the wrong type of Exception is thrown in the body of the test.

Parameters:

actualException - the actual exception thrown

Returns:

the message for the given exception

getActualException

public final Exception getActualException()

Expose the actual exception thrown from test(), if any.

Returns:

the actual exception, or null if none