@Test
	public void testNavigationKeysTriggerCompletionWindowToShow() {

		// insert some text and make sure the window is created
		typeText("d", true);

		// hide the window to test its triggering on up		
		hideWindowPressKeyThenValidate(KeyEvent.VK_UP);

		// hide the window to test its triggering on down
		hideWindowPressKeyThenValidate(KeyEvent.VK_DOWN);

		// hide the window to test its triggering on keypad up
		hideWindowPressKeyThenValidate(KeyEvent.VK_KP_UP);

		// hide the window to test its triggering on keypad down
		hideWindowPressKeyThenValidate(KeyEvent.VK_KP_DOWN);

		// now with no text in the text field
		clearText();
		JWindow matchingWindow = textField.getActiveMatchingWindow();
		assertTrue("The completion window is showing after a clearing the text field",
			!matchingWindow.isShowing());

		up();
		assertTrue("The completion window is showing after pressing the up key in the text field " +
			"while the text field is empty", !matchingWindow.isShowing());

		down();
		assertTrue(
			"The completion window is showing after pressing the down key in the text field" +
				"while the text field is empty",
			!matchingWindow.isShowing());
	}
This test achieves partial coverage of {@link DropDownTextField}.  Further coverage is
provided by {@link DropDownSelectionTextFieldTest}, as that test enables item selection 
in the widget being tested.
Ghidra/Framework/Docking/src/test/java/docking/widgets/DropDownTextFieldTest.java