reuse closure when creating and testing

HHVM makes different closures objects that don't compare to the original functions.

    1) ValidationFactoryTest::testMakeMethodCreatesValidValidator
    Failed asserting that two arrays are equal.
    --- Expected
    +++ Actual
    @@ @@
     Array (
    -    'foo' => Closure$ValidationFactoryTest::testMakeMethodCreatesValidValidator#3 Object ()
    -    'implicit' => Closure$ValidationFactoryTest::testMakeMethodCreatesValidValidator#4 Object ()
    +    'foo' => Closure$ValidationFactoryTest::testMakeMethodCreatesValidValidator Object ()
    +    'implicit' => Closure$ValidationFactoryTest::testMakeMethodCreatesValidValidator#2 Object ()
     )

Instead I think this test really wants to make sure the same closure went in and came out again.