diff --git a/tests/test_variableparameters.py b/tests/test_variableparameters.py
index 9504182..c3dd917 100644
--- a/tests/test_variableparameters.py
+++ b/tests/test_variableparameters.py
@@ -189,6 +189,24 @@ def test_unit_forammter():
     fmt = unit_formatter("s", 4, vmin=None)
     assert fmt(5e-29) == "5e-05ys"
 
+    fmt = unit_formatter("%", 4)
+    assert fmt(1.000001235) == "100%"
+    assert fmt(0.01235) == "1.235%"
+    assert fmt(0.001235) == "0.1235%"
+    assert fmt(0.0001235) == "0.01235%"
+    assert fmt(0.00001235) == "0.001235%"
+    assert fmt(0.000001235) == "0.0001235%"
+    assert fmt(0.0000001235) == "1.235e-05%"
+    assert fmt(0.00000001235) == "1.235e-06%"
+    assert fmt(0.000000001235) == "1.235e-07%"
+
+    fmt = unit_formatter("%", 2)
+    assert fmt(0.01235) == "1.2%"
+    assert fmt(0.001235) == "0.12%"
+    assert fmt(1.000001235) == "1e+02%"
+    assert fmt(0.000001235) == "0.00012%"
+    assert fmt(0.000000001235) == "1.2e-07%"
+
 
 def test_param_formatting():
     """formatting is always respected"""