diff --git a/tests/common.py b/tests/common.py
index e4c58dcc..092d69a6 100644
--- a/tests/common.py
+++ b/tests/common.py
@@ -73,7 +73,7 @@ class RequestWrongOrder(Exception):
         self.exp_method = exp_method
 
     def __str__(self):
-        return '%s, %s, %s, %s' % (self.url, self.exp_url, self.method, self.exp_method)
+        return f'{self.url}, {self.exp_url}, {self.method}, {self.exp_method}'
 
 
 class RequestDataMismatch(Exception):
@@ -85,7 +85,7 @@ class RequestDataMismatch(Exception):
         self.exp = exp
 
     def __str__(self):
-        return '%s, %s, %s' % (self.url, self.got, self.exp)
+        return f'{self.url}, {self.got}, {self.exp}'
 
 
 EXPECTED_REQUESTS = []
diff --git a/tests/test_repairwc.py b/tests/test_repairwc.py
index 30f85e44..c69725ce 100644
--- a/tests/test_repairwc.py
+++ b/tests/test_repairwc.py
@@ -25,7 +25,7 @@ class TestRepairWC(OscTestCase):
         try:
             meth(*args, **kwargs)
         except exception:
-            self.fail('%s raised' % exception.__name__)
+            self.fail(f'{exception.__name__} raised')
 
     def test_working_empty(self):
         """consistent, empty working copy"""