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POHow can I prevent QuickCheck from catching all exceptions?
 

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  1. POHow can I prevent QuickCheck from catching all exceptions?
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    <p>The QuickCheck library seems to catch all exceptions that are thrown when testing a property. In particular, this behavior prevents me from putting a time limit on the entire QuickCheck computation. For example:</p> <pre><code>module QuickCheckTimeout where import System.Timeout (timeout) import Control.Concurrent (threadDelay) import Test.QuickCheck (quickCheck, within, Property) import Test.QuickCheck.Monadic (monadicIO, run, assert) -- use threadDelay to simulate a slow computation prop_slow_plus_zero_right_identity :: Int -&gt; Property prop_slow_plus_zero_right_identity i = monadicIO $ do run (threadDelay (100000 * i)) assert (i + 0 == i) runTests :: IO () runTests = do result &lt;- timeout 3000000 (quickCheck prop_slow_plus_zero_right_identity) case result of Nothing -&gt; putStrLn "timed out!" Just _ -&gt; putStrLn "completed!" </code></pre> <p>Because QuickCheck catches all the exceptions, <code>timeout</code> breaks: it doesn't actually abort the computation! Instead, QuickCheck treats the property as having failed, and tries to shrink the input that caused the failure. This shrinking process is then not run with a time bound, causing the total time used by the computation to exceed the prescribed time limit.</p> <p>One might think I could use QuickCheck's <code>within</code> combinator to bound the computation time. (<code>within</code> treats a property as having failed if it doesn't finish within the given time limit.) However, <code>within</code> doesn't quite do what I want, since QuickCheck still tries to shrink the input that caused the failure, a process that can take far too long. (What could alternatively work for me is a version of <code>within</code> that prevents QuickCheck from trying to shrink the inputs to a property that failed because it didn't finish within the given time limit.)</p> <p>How can I prevent QuickCheck from catching all exceptions?</p>
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