	@Test
	void incompleteRule() {

		final List<Token> tokens = Arrays.asList(
				new Token(EXISTENCE, "existence", 0),
				new Token(IDENTIFIER, "test", 0),
				new Token(COLON, ":", 0),
				new Token(IDENTIFIER, "x", 0),
				new Token(PLUS, "+", 0),
				new Token(IDENTIFIER, "y", 0),
				new Token(ARROW, "->", 0),
				new Token(EOF, "", 0)
		);
		final Parser parser = new Parser(tokens, errors::add);

		assertTrue(parser.parse().isEmpty());

		final List<DslError> expectedErrors = Collections.singletonList(new UnexpectedToken(
				new Token(EOF, "", 0)
		));
		assertEquals(expectedErrors, errors);
	}