diff --git a/tests/data/string.ccl b/tests/data/string.ccl
new file mode 100644
index 0000000000000000000000000000000000000000..69dd884c6e5eca3f4b1de6e259c49225cd28688c
--- /dev/null
+++ b/tests/data/string.ccl
@@ -0,0 +1,26 @@
+tagset=kipi
+---
+lower(["pałąk", "Pałąk", "PAŁĄK", "pałĄK"])
+
+["pałąk"]
+---
+upper(["żółć", "ŻÓŁĆ", "Żółć", "żÓłĆ"])
+
+["ŻÓŁĆ"]
+---
+upper(["Schlüssel", "ěêĕ"])
+
+["SCHLÜSSEL", "ĚÊĔ"]
+---
+affix(["pijÄ…cy", "jedzÄ…cy", "jedzÄ…ca", "ca"], -3)
+
+["Ä…ca", "Ä…cy", "ca"]
+---
+affix(["ökonomisch", "ökologisch", "oko", "okoń", "ok"], 3)
+
+["ok", "oko", "öko"]
+---
+affix(["psi", "pies"], 0)
+
+["pies", "psi"]
+---