diff --git a/gram/test/test_common.py b/gram/test/test_common.py
index 7205478..f775ea1 100644
--- a/gram/test/test_common.py
+++ b/gram/test/test_common.py
@@ -17,6 +17,28 @@ def generic_test(txxd):
         generic_test(5)
         generic_test(10)
 
+    def test_delay(self):
+        def generic_test(txxd):
+            dut = tXXDController(txxd)
+
+            yield dut.valid.eq(1)
+            yield; yield Delay(1e-8)
+            self.assertFalse((yield dut.ready))
+
+            yield dut.valid.eq(0)
+
+            for i in range(txxd):
+                self.assertFalse((yield dut.ready))
+                yield
+
+            self.assertTrue((yield dut.ready))
+
+            runSimulation(dut, process, "test_common_txxdcontroller.vcd")
+
+        generic_test(1)
+        generic_test(5)
+        generic_test(10)
+
 class tFAWControllerTestCase(FHDLTestCase):
     def test_strobe_3(self):
         dut = tFAWController(10)