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johnjcamilleri/unsafePerformIO vs monadicIO.run

Last active August 29, 2015 14:11
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QuickCheck.Monadic
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unsafePerformIO vs monadicIO.run
> quickCheck (property True)
+++ OK, passed 100 tests.
> quickCheck (property False)
*** Failed! Falsifiable (after 1 test):
> quickCheck (unsafePerformIO $ return $ property True)
+++ OK, passed 100 tests.
> quickCheck (unsafePerformIO $ return $ property False)
*** Failed! Falsifiable (after 1 test):
> quickCheck (monadicIO $ run $ return $ property True)
+++ OK, passed 100 tests.
> quickCheck (monadicIO $ run $ return $ property False)
+++ OK, passed 100 tests.
@johnjcamilleri
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Why is line 14 passing?

@johnjcamilleri
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I was using monadicIO incorrectly. Should be:

> quickCheck (monadicIO $ run (return False) >>= assert)
*** Failed! Assertion failed (after 1 test):

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