diff --git a/pyopencl/array.py b/pyopencl/array.py
index a0f7805ce63f02e7e2d3e3a6b2c7aba7ccd0b23d..a93c947e29ba8d3d9d213240fb9598717313f189 100644
--- a/pyopencl/array.py
+++ b/pyopencl/array.py
@@ -216,16 +216,19 @@ class _ArrayFlags:
         self.array = ary
 
     @property
+    @memoize_method
     def f_contiguous(self):
         return self.array.strides == _f_contiguous_strides(
                 self.array.dtype.itemsize, self.array.shape)
 
     @property
+    @memoize_method
     def c_contiguous(self):
         return self.array.strides == _c_contiguous_strides(
                 self.array.dtype.itemsize, self.array.shape)
 
     @property
+    @memoize_method
     def forc(self):
         return self.f_contiguous or self.c_contiguous
 
@@ -332,6 +335,7 @@ class Array(object):
         self.context = self.data.context
 
     @property
+    @memoize_method
     def flags(self):
         return _ArrayFlags(self)
 
diff --git a/pyopencl/tools.py b/pyopencl/tools.py
index 8a25b801e5eeec477eff93a507e8d6589adc0bb9..a124600f85fc5c0a9d64e794ecfd64afd887f8f7 100644
--- a/pyopencl/tools.py
+++ b/pyopencl/tools.py
@@ -72,6 +72,12 @@ def pytest_generate_tests_for_pyopencl(metafunc):
             self.device = device
 
         def __call__(self):
+            # Get rid of leftovers from past tests.
+            # CL implementations are surprisingly limited in how many
+            # simultaneous contexts they allow...
+            from gc import collect
+            collect()
+
             return cl.Context([device])
 
         def __str__(self):