diff --git a/tests/test_rdrgen.py b/tests/test_rdrgen.py
index ab0deb1ee07418cd9dcd9be40fe4883a07524fe4..da92a0c05c14172622e8e346be0714c6a6495dc5 100644
--- a/tests/test_rdrgen.py
+++ b/tests/test_rdrgen.py
@@ -10,8 +10,9 @@ import edosl0util.rdrgen as m
 from edosl0util.jpssrdr import decode_rdr_blob
 from edosl0util.stream import jpss_packet_stream
 
-if 'CI' in os.environ:
-    pytest.skip('skipping rdrgen tests (CI: h5diff not available)',
+h5diff_available = (subprocess.call('which h5diff > /dev/null 2>&1', shell=True) == 0)
+if not h5diff_available:
+    pytest.skip('skipping rdrgen tests (h5diff not available)',
                 allow_module_level=True)