Basic test for the memory pressure simulation mechanism.

On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".


Verify that we're not running under memory pressure from the beginning.
PASS internals.isUnderMemoryPressure is false
Begin simulated memory pressure.
PASS internals.isUnderMemoryPressure is true
End simulated memory pressure.
PASS internals.isUnderMemoryPressure is false
PASS successfullyParsed is true

TEST COMPLETE