@Test(expected = NullPointerException.class)
    public void shouldThrowIfAfterFunctionIsNull() {
        final TriFunction<String, String, String, String> f = (a, b, c) -> a + b + c;
        f.andThen(null);
    }
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/util/function/TriFunctionTest.java