@Test
    @LoadGraphWith(MODERN)
    public void shouldThrowNiceExceptionWhenMapKeyNotFoundInMathStep() {
        try {
            g.V().hasLabel("person").project("age").by("age").as("x").math("x").by("aged").iterate();
            fail("Traversal should no have succeeded since the 'aged' key does not exist");
        } catch (IllegalStateException ise) {
            assertThat(ise.getMessage(), startsWith("The variable x for math() step must resolve to a Number"));
        }
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
@author Pieter Martin
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/CoreTraversalTest.java