public class MyDslValidatorTest extends AbstractXtextTests {

  private ValidatorTester<MyDslJavaValidator> tester;

  @Override
  protected void setUp() throws Exception {
    super.setUp();
    with(MyDslStandaloneSetup.class);
    MyDslJavaValidator validator = get(MyDslJavaValidator.class);
    tester = new ValidatorTester<MyDslJavaValidator>(validator, getInjector());
  }

  public void testE00001() {
    try {
      URL url = MyDslValidatorTest.class.getResource("error/e00001.smi");
      Resource resource = getResource(url.openStream());

      Model model = (Model) resource.getContents().get(0);
      
      // ??? tester.validator().validate(model); ???
      tester.diagnose().assertErrorContains(IMessageCodes.E_00001);      
    }
    catch (Exception e) {
      fail(e.getMessage());
    }
  }

private ValidatorTester<MyDslJavaValidator> tester;
...
public void testE00001() throws Exception {
    URL url = MyDslValidatorTest.class.getResource("error/e00001.dsl");
    Resource resource = getResource(url.openStream());

    Model model = (Model) resource.getContents().get(0);
    AssertableDiagnostics result = tester.validate(model);
    result.assertErrorContains(IMessageCodes.E_00001);
}