@Test
public void exists() {

    assertTrue(importer.exists(new FileDataSource(fileSystem.getPath("/"), "test0")));
    assertTrue(importer.exists(new FileDataSource(fileSystem.getPath("/"), "test1")));
    assertTrue(importer.exists(new FileDataSource(fileSystem.getPath("/"), "test2")));
    assertFalse(importer.exists(new FileDataSource(fileSystem.getPath("/"), "test3"))); // wrong extension
    assertFalse(importer.exists(new FileDataSource(fileSystem.getPath("/"), "test4"))); // does not exist
    assertFalse(importer.exists(new FileDataSource(fileSystem.getPath("/"), "testDummy"))); // namespace URI is not defined
}