diff --git a/test/full_stack.py b/test/full_stack.py
index 7b87d7cfe..73203b636 100644
--- a/test/full_stack.py
+++ b/test/full_stack.py
@@ -7,7 +7,7 @@ from artiq.coredevice import comm_serial, core, runtime_exceptions, rtio
 from artiq.sim import devices as sim_devices
 
 
-NO_HARDWARE = bool(os.getenv("ARTIQ_NO_HARDWARE"))
+no_hardware = bool(os.getenv("ARTIQ_NO_HARDWARE"))
 
 
 def _run_on_device(k_class, **parameters):
@@ -136,7 +136,7 @@ class _Exceptions(AutoContext):
                 self.trace.append(104)
 
 
-@unittest.skipIf(NO_HARDWARE, "no hardware")
+@unittest.skipIf(no_hardware, "no hardware")
 class ExecutionCase(unittest.TestCase):
     def test_primes(self):
         l_device, l_host = [], []
@@ -208,8 +208,10 @@ class _RTIOSequenceError(AutoContext):
         self.o.pulse(25*us)
 
 
-@unittest.skipIf(NO_HARDWARE, "no hardware")
+@unittest.skipIf(no_hardware, "no hardware")
 class RTIOCase(unittest.TestCase):
+    # Connect channels 0 and 1 together for this test
+    # (C11 and C13 on Papilio Pro)
     def test_loopback(self):
         npulses = 4
         with comm_serial.Comm() as comm: