org.junit
Annotation Type Test
The Test
annotation tells JUnit that the public void
method to which it is attached can be run as a test case. To run the method, JUnit first constructs a fresh instance of the class then invokes the annotated method. Any exceptions thrown by the test will be reported by JUnit as a failure. If no exceptions are thrown, the test is assumed to have succeeded.
A simple test looks like this:
public class Example { @Test public void method() { org.junit.Assert.assertTrue( new ArrayList().isEmpty() ); } }
The Test
annotation supports two optional parameters for exception testing and for limiting test execution time.
Exception Testing
The parameter expected
declares that a test method should throw an exception. If it doesn't throw an exception or if it throws a different exception than the one declared, the test fails. For example, the following test succeeds:
@Test(expected=IndexOutOfBoundsException.class) public void outOfBounds() { new ArrayList<Object>().get(1); }Using the parameter
expected
for exception testing comes with some limitations: only the exception's type can be checked and it is not possible to precisely specify the code that throws the exception. Therefore JUnit 4 has improved its support for exception testing with
Assert.assertThrows(Class, ThrowingRunnable)
and the
ExpectedException
rule. With
assertThrows
the code that throws the exception can be precisely specified. If the exception's message or one of its properties should be verified, the
ExpectedException
rule can be used. Further information about exception testing can be found at the
JUnit Wiki.
Timeout
The parameter timeout
causes a test to fail if it takes longer than a specified amount of clock time (measured in milliseconds). The following test fails:
@Test(timeout=100) public void infinity() { while(true); }Warning: while
timeout
is useful to catch and terminate infinite loops, it should
not be considered deterministic. The following test may or may not fail depending on how the operating system schedules threads:
@Test(timeout=100) public void sleep100() { Thread.sleep(100); }THREAD SAFETY WARNING: Test methods with a timeout parameter are run in a thread other than the thread which runs the fixture's @Before and @After methods. This may yield different behavior for code that is not thread safe when compared to the same test method without a timeout parameter. Consider using the
Timeout
rule instead, which ensures a test method is run on the same thread as the fixture's @Before and @After methods.
- Since:
- 4.0
Optional Element Summary | |
---|---|
Class<? extends Throwable> |
expected Optionally specify expected , a Throwable, to cause a test method to succeed if and only if an exception of the specified class is thrown by the method. |
long |
timeout Optionally specify timeout in milliseconds to cause a test method to fail if it takes longer than that number of milliseconds. |
expected
public abstract Class<? extends Throwable> expected
-
Optionally specify
expected
, a Throwable, to cause a test method to succeed if and only if an exception of the specified class is thrown by the method. If the Throwable's message or one of its properties should be verified, theExpectedException
rule can be used instead. -
-
- Default:
- org.junit.Test.None.class
timeout
public abstract long timeout
-
Optionally specify
timeout
in milliseconds to cause a test method to fail if it takes longer than that number of milliseconds.THREAD SAFETY WARNING: Test methods with a timeout parameter are run in a thread other than the thread which runs the fixture's @Before and @After methods. This may yield different behavior for code that is not thread safe when compared to the same test method without a timeout parameter. Consider using the
Timeout
rule instead, which ensures a test method is run on the same thread as the fixture's @Before and @After methods. -
-
- Default:
- 0L