Increase timing in cache tests (#336)

* increase sleep times a bit in cache tests

attempting to avoid stochastic test failures on MacOS CI jobs

tests/test_pyfftw_interfaces_cache.py

@@ -34,6 +34,7 @@
 #
 
 import copy
+import sys
 
 from pyfftw import interfaces, builders
 import pyfftw
@@ -187,7 +188,7 @@ def test_cache_parent_thread_ended(self):
         '''
         # Firstly make sure we've exited any lingering threads from other
         # tests.
-        time.sleep(0.1)
+        time.sleep(0.25)
 
         self.assertTrue(_check_n_cache_threads_running() == 0)
 
@@ -201,12 +202,12 @@ def cache_parent_thread():
             target=cache_parent_thread, name='PyFFTWCacheThread')
         parent_t.start()
 
-        time.sleep(0.1)
+        time.sleep(0.25)
         # Check it's running
         self.assertTrue(_check_n_cache_threads_running() == 2)
 
         parent_t.join()
-        time.sleep(0.1)
+        time.sleep(0.25)
         # Check both threads have exited properly
         self.assertTrue(_check_n_cache_threads_running() == 0)
 
@@ -215,15 +216,15 @@ def test_delete_cache_object(self):
         '''
         # Firstly make sure we've exited any lingering threads from other
         # tests.
-        time.sleep(0.2)
+        time.sleep(0.25)
         self.assertTrue(_check_n_cache_threads_running() == 0)
 
         _cache = interfaces.cache._Cache()
-        time.sleep(0.2)
+        time.sleep(0.25)
         self.assertTrue(_check_n_cache_threads_running() == 1)
 
         del _cache
-        time.sleep(0.2)
+        time.sleep(0.25)
         self.assertTrue(_check_n_cache_threads_running() == 0)
 
     @unittest.skipIf(*miss('64'))
@@ -298,10 +299,8 @@ def test_objects_removed_after_keepalive(self):
 
         keepalive_time = _cache.keepalive_time
 
-        if os.name == 'nt':
-            # A hack to keep appveyor from falling over here. I suspect the
-            # contention is too much to work properly. Either way, let's
-            # assume it's a windows problem for now...
+        if os.name == 'nt' or sys.platform == 'darwin':
+            # increase sleep time to address random test failures on CI
             time.sleep(keepalive_time * 8)
         else:
             # Relax a bit more otherwise