Examples of org.junit.runners.Parameterized

The custom runner Parameterized implements parameterized tests. When running a parameterized test class, instances are created for the cross-product of the test methods and the test data elements.

For example, to test a Fibonacci function, write:

 @RunWith(Parameterized.class) public class FibonacciTest { @Parameters(name= "{index}: fib[{0}]={1}") public static Iterable<Object[]> data() { return Arrays.asList(new Object[][] { { 0, 0 }, { 1, 1 }, { 2, 1 }, { 3, 2 }, { 4, 3 }, { 5, 5 }, { 6, 8 } }); } private int fInput; private int fExpected; public FibonacciTest(int input, int expected) { fInput= input; fExpected= expected; } @Test public void test() { assertEquals(fExpected, Fibonacci.compute(fInput)); } }

Each instance of FibonacciTest will be constructed using the two-argument constructor and the data values in the @Parameters method.

In order that you can easily identify the individual tests, you may provide a name for the @Parameters annotation. This name is allowed to contain placeholders, which are replaced at runtime. The placeholders are

{index}: the current parameter index
{0}: the first parameter value
{1}: the second parameter value
...: ...

In the example given above, the Parameterized runner creates names like [1: fib(3)=2]. If you don't use the name parameter, then the current parameter index is used as name.

You can also write:

 @RunWith(Parameterized.class) public class FibonacciTest { @Parameters public static Iterable<Object[]> data() { return Arrays.asList(new Object[][] { { 0, 0 }, { 1, 1 }, { 2, 1 }, { 3, 2 }, { 4, 3 }, { 5, 5 }, { 6, 8 } }); } @Parameter(0) public int fInput; @Parameter(1) public int fExpected; @Test public void test() { assertEquals(fExpected, Fibonacci.compute(fInput)); } }

Each instance of FibonacciTest will be constructed with the default constructor and fields annotated by @Parameter will be initialized with the data values in the @Parameters method.

The parameters can be provided as an array, too:

 @Parameters public static Object[][] data() { return new Object[][] { { 0, 0 }, { 1, 1 }, { 2, 1 }, { 3, 2 }, { 4, 3 }, { 5, 5 }, { 6, 8 } }; }

Tests with single parameter

If your test needs a single parameter only, you don't have to wrap it with an array. Instead you can provide an Iterable or an array of objects.

 @Parameters public static Iterable<? extends Object> data() { return Arrays.asList("first test", "second test"); }

 @Parameters public static Object[] data() { return new Object[] { "first test", "second test" }; }

Create different runners

By default the {@code Parameterized} runner creates a slightly modified{@link BlockJUnit4ClassRunner} for each set of parameters. You can build anown {@code Parameterized} runner that creates another runner for each set ofparameters. Therefore you have to build a {@link ParametersRunnerFactory}that creates a runner for each {@link TestWithParameters}. ( {@code TestWithParameters} are bundling the parameters and the test name.)The factory must have a public zero-arg constructor.

 public class YourRunnerFactory implements ParameterizedRunnerFactory { public Runner createRunnerForTestWithParameters(TestWithParameters test) throws InitializationError { return YourRunner(test); } }

Use the {@link UseParametersRunnerFactory} to tell the {@code Parameterized}runner that it should use your factory.

 @RunWith(Parameterized.class) @UseParametersRunnerFactory(YourRunnerFactory.class) public class YourTest { ... }

@since 4.0