@Test
    public void shouldApplyKeyOnVertexProperty() {
        final VertexProperty e = mock(VertexProperty.class);
        when(e.key()).thenReturn("keyName");

        assertEquals("keyName", T.key.apply(e));
    }
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/structure/TTest.java