Test suite: wrap some properties in once

Prior to `QuickCheck-2.15`, properties without any quantification (e.g.,
`quickCheck True`) would only be run a single time. This is no longer the case
in `QuickCheck-2.15` or later, as these properties will now be run multiple
times, just like properties with arguments.

We use `ioProperty` to define a small number properties without any arguments
in the `copilot-bluespec` test suite. Unfortunately, this means that we were
previously compiling and simulating, say, 7 Bluespec programs prior to
`QuickCheck-2.15`, but we now we are compiling and simulating _700_ Bluespec
programs after `QuickCheck-2.15`. This means that it takes an extraordinarily
long time to run the test suite using `QuickCheck-2.15`.

This patch restores the old behavior of pre-2.15 versions of `QuickCheck` by
wrapping these properties in `once`.

tests/Test/Copilot/Compile/Bluespec.hs

@@ -31,8 +31,9 @@ import Test.Framework.Providers.QuickCheck2 (testProperty)
 import Test.QuickCheck                      (Arbitrary, Gen, Property,
                                              arbitrary, choose, elements,
                                              forAll, forAllBlind, frequency,
-                                             getPositive, ioProperty, oneof,
-                                             vectorOf, withMaxSuccess, (.&&.))
+                                             getPositive, ioProperty, once,
+                                             oneof, vectorOf, withMaxSuccess,
+                                             (.&&.))
 import Test.QuickCheck.Gen                  (chooseAny, chooseBoundedIntegral)
 
 -- External imports: Copilot
@@ -65,7 +66,7 @@ tests =
 
 -- | Test compiling a spec.
 testCompile :: Property
-testCompile = ioProperty $ do
+testCompile = once $ ioProperty $ do
     tmpDir <- getTemporaryDirectory
     setCurrentDirectory tmpDir
 
@@ -97,7 +98,7 @@ testCompile = ioProperty $ do
 
 -- | Test compiling a spec in a custom directory.
 testCompileCustomDir :: Property
-testCompileCustomDir = ioProperty $ do
+testCompileCustomDir = once $ ioProperty $ do
     tmpDir <- getTemporaryDirectory
     setCurrentDirectory tmpDir
 
@@ -135,7 +136,7 @@ testCompileCustomDir = ioProperty $ do
 --
 -- The actual behavior is ignored.
 testRun :: Property
-testRun = ioProperty $ do
+testRun = once $ ioProperty $ do
     tmpDir <- getTemporaryDirectory
     setCurrentDirectory tmpDir
 
@@ -261,6 +262,7 @@ mkRegressionTest2 op haskellFun vals =
                     ]
         outputs = haskellFun vals1 vals2 in
 
+    once $
     testRunCompareArg
       inputs len outputs spec (typeBluespec t3)