@Test
public void testCopyWithExtension() {

    LoadFlowParameters parameters = new LoadFlowParameters();
    DummyExtension dummyExtension = new DummyExtension();
    parameters.addExtension(DummyExtension.class, dummyExtension);
    LoadFlowParameters copy = parameters.copy();
    assertEquals(1, copy.getExtensions().size());
    Extension<LoadFlowParameters> copiedExt = copy.getExtensionByName("dummyExtension");
    assertSame(parameters, dummyExtension.getExtendable());
    assertSame(copy, copiedExt.getExtendable());
}