diff --git a/tests/common-pattern.py b/tests/common-pattern.py
new file mode 100644
--- /dev/null
+++ b/tests/common-pattern.py
@@ -0,0 +1,9 @@
+# common patterns in test at can safely be replaced
+from __future__ import absolute_import
+
+substitutions = [
+    # list of possible compressions
+    (br'zstd,zlib,none,bzip2',
+     br'$USUAL_COMPRESSIONS$'
+    ),
+]