@Test
  public void testDeleteAllEntities() {

    TestEntity t1 = new TestEntity();
    t1.setStringProperty(String.format("1"));

    TestEntity t2 = new TestEntity();
    t2.setStringProperty(String.format("2"));

    repository.save(Arrays.asList(t1, t2));
    repository.deleteAll();

    assertNull("Checking that the result is null.", repository.findById(t1.getId()));
    assertNull("Checking that the result is null.", repository.findById(t2.getId()));
  }