Why not use the ParameterizedTestRunner from JUnit?

As already stated this project was developed for the JUnitRecorder project. It was necessary to overcome some shortcomings of the JUnit ParameterizedTestRunner which is directly provided by JUnit.

Let's take a look at a plain JUnit test i with a ParameterizedTestRunner:

@RunWith(Parameterized.class)
public class XStreamControlCharTest
{
  private XStream myXStream;

  private String myOrginalString;
  private String myExpectedXml;

  @Before
  public void before() {
    myXStream = new XStream(new HideControlCharXppDriver());
  }

  public XStreamControlCharTest(String orginalString, String expectedXML)
  {
    myOrginalString = orginalString;
    myExpectedXml = expectedXML;
  }

  @Parameters
  public static Collection getMocks() {
    return Arrays.asList(new Object[][] {
      /* 0 */{"HelloWorld", "<string>HelloWorld</string>"}
      /* 1 */, {"Hello World", "<string>Hello World</string>"}
    [...]
      /* 21 */, {"\\{0}", "<string>\\\\{0}</string>"}});
  }

  @Test
  public void runTest() {
    String xml = myXStream.toXML(myOrginalString);
    // Serialization Test
    assertEquals(myExpectedXml, xml);

    String neu = (String) myXStream.fromXML(xml);
    // deserialization Test
    assertEquals(myOrginalString, neu);
  }

}  

One 'Data provider'

Per test class only one data Array can be defined. It is possible to annotate more methods with "@Parameters" but still per class only one (merged) test data list is available. It's not possible to specify test data lists per test method.

Data inside test

Not necessarily a problem, but having the test data inside the tests can get ugly when the data is getting bigger.

Dependency injection only by constructor

The 'dependencies' are injected into the Constructor so in most cases you will need a private member per parameter to transport the injected values into your actual test.

One test class per method not per class

When writing manual tests you have normally per class to test one corresponding test-class. In the test-class there are multiple test methods testing ALL your method. With the JUnit ParameteriezdTestRunner you have one class per method!

To overcome this shortcomings the JUnit Parameterized Test module was created:

One 'Data provider'

Per test method a data provider can be specified.

Data inside test

The default 'Data provider' reads the test Data from an XML resource file. But the providers are exchangeable so you can just provide your own, which can retrieve the data from virtually anywhere.

Dependency injection only by constructor

The tests data is injected directly into your test method. a constructor injection is not possible.

One test class per method not per class

Because test data are now provided per test method you can specify multiple test data per class and therefore one test class is possible again.

How this is really achieved you should continue reading the Usage .