Adds test for robinhood#674 that fails only on Cython

t/cython/test_cython.py

@@ -7,8 +7,10 @@ class test_Cython:
     This test is here to ensure we get a clear indication if e.g. Travis
     fails to correctly install Cython and build our modules
     """
-    @pytest.mark.skipif(not bool(os.environ.get("USE_CYTHON")), reason="Cython not enabled")
-    @pytest.mark.skipif(bool(os.environ.get('NO_CYTHON', False)), reason="Cython disabled")
+    @pytest.mark.skipif(not bool(os.environ.get('USE_CYTHON')),
+                        reason='Cython not enabled')
+    @pytest.mark.skipif(bool(os.environ.get('NO_CYTHON', False)),
+                        reason='Cython disabled')
     def test_import(self):
         from faust._cython.windows import HoppingWindow
         HoppingWindow(60, 60)

t/unit/windows/test_hopping_window.py

@@ -1,3 +1,4 @@
+from pytest import approx
 from faust.windows import HoppingWindow
 
 
@@ -59,3 +60,19 @@ def test_stale_timestamp(self):
         for time in range(0, now_timestamp - expires):
             print(f'TIME: {time} NOW TIMESTAMP: {now_timestamp}')
             assert window.stale(time, now_timestamp) is True
+
+    def test_ranges_types(self):
+        size = 60
+        step = 60
+        window = HoppingWindow(size, step)
+
+        # There's nothing special about this timestamp,
+        # it was simply when the test was created
+        timestamp = 1603122451.544989
+        window_ranges = window.ranges(timestamp)
+
+        assert len(window_ranges) == 1
+        assert type(window_ranges[0][0]) == float
+        assert type(window_ranges[0][1]) == float
+        assert window_ranges[0][0] == approx(1603122420.0)
+        assert window_ranges[0][1] == approx(1603122479.9)