Package org.junit.runners

Class Parameterized

  • All Implemented Interfaces:
    Describable, Filterable, Orderable, Sortable
    public class Parameterized
extends Suite
    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 the + operator, write: 

     @RunWith(Parameterized.class)
 public class AdditionTest {
     @Parameters(name = "{index}: {0} + {1} = {2}")
     public static Iterable<Object[]> data() {
         return Arrays.asList(new Object[][] { { 0, 0, 0 }, { 1, 1, 2 },
                 { 3, 2, 5 }, { 4, 3, 7 } });
     }

     private int firstSummand;

     private int secondSummand;

     private int sum;

     public AdditionTest(int firstSummand, int secondSummand, int sum) {
         this.firstSummand = firstSummand;
         this.secondSummand = secondSummand;
         this.sum = sum;
     }

     @Test
     public void test() {
         assertEquals(sum, firstSummand + secondSummand);
     }
 }

    Each instance of AdditionTest will be constructed using the three-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 [2: 3 + 2 = 5]. 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 AdditionTest {
     @Parameters(name = "{index}: {0} + {1} = {2}")
     public static Iterable<Object[]> data() {
         return Arrays.asList(new Object[][] { { 0, 0, 0 }, { 1, 1, 2 },
                 { 3, 2, 5 }, { 4, 3, 7 } });
     }

     @Parameter(0)
     public int firstSummand;

     @Parameter(1)
     public int secondSummand;

     @Parameter(2)
     public int sum;

     @Test
     public void test() {
         assertEquals(sum, firstSummand + secondSummand);
     }
 }

    Each instance of AdditionTest 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, 0 }, { 1, 1, 2 }, { 3, 2, 5 }, { 4, 3, 7 } } };
 }

    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");
 }

    or 

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

    Executing code before/after executing tests for specific parameters

    If your test needs to perform some preparation or cleanup based on the parameters, this can be done by adding public static methods annotated with @BeforeParam/@AfterParam. Such methods should either have no parameters or the same parameters as the test. 

     @BeforeParam
 public static void beforeTestsForParameter(String onlyParameter) {
     System.out.println("Testing " + onlyParameter);
 }

    Create different runners

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

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

    Use the Parameterized.UseParametersRunnerFactory to tell the Parameterized runner that it should use your factory. 

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

    Avoid creating parameters

    With assumptions you can dynamically skip tests. Assumptions are also supported by the @Parameters method. Creating parameters is stopped when the assumption fails and none of the tests in the test class is executed. JUnit reports a single assumption failure for the whole test class in this case. 

     @Parameters
 public static Iterable<? extends Object> data() {
        String os = System.getProperty("os.name").toLowerCase()
        Assume.assumeTrue(os.contains("win"));
        return Arrays.asList("first test", "second test");
 }
    Since:
    4.0

    • Constructor Detail

      • Parameterized

        public Parameterized​(java.lang.Class<?> klass)
              throws java.lang.Throwable
        Only called reflectively. Do not use programmatically.
        Throws:
        java.lang.Throwable