@Parameterized.Parameters(name = "expect({0})")
        public static Iterable<Object[]> data() {
            return Arrays.asList(new Object[][]{
                    {"variableValueCanNotBeNull", "k", null, Graph.Variables.Exceptions.variableValueCanNotBeNull()},
                    {"variableKeyCanNotBeNull", null, "v", Graph.Variables.Exceptions.variableKeyCanNotBeNull()},
                    {"variableKeyCanNotBeEmpty", "", "v", Graph.Variables.Exceptions.variableKeyCanNotBeEmpty()}});
        }
Test exceptions around {@link Graph.Variables}.
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/structure/VariablesTest.java