diff --git a/authentication/authentication_test.go b/authentication/authentication_test.go
index 4acd2f8a..f19e1134 100644
--- a/authentication/authentication_test.go
+++ b/authentication/authentication_test.go
@@ -471,7 +471,9 @@ func TestWithClockTolerance(t *testing.T) {
 			return
 		}
 		w.WriteHeader(http.StatusOK)
-		fmt.Fprint(w, string(b))
+		if _, err := fmt.Fprint(w, string(b)); err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+		}
 	})
 	s := httptest.NewTLSServer(h)
 	t.Cleanup(func() {
diff --git a/authentication/oauth_test.go b/authentication/oauth_test.go
index 5fc996fb..ef0fa9b6 100644
--- a/authentication/oauth_test.go
+++ b/authentication/oauth_test.go
@@ -514,7 +514,9 @@ func withIDToken(t *testing.T, extras map[string]interface{}) (*Authentication,
 			return
 		}
 		w.WriteHeader(http.StatusOK)
-		fmt.Fprint(w, string(b))
+		if _, err := fmt.Fprint(w, string(b)); err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+		}
 	})
 	s := httptest.NewTLSServer(h)
 	t.Cleanup(func() {
diff --git a/internal/idtokenvalidator/idtokenvalidator_test.go b/internal/idtokenvalidator/idtokenvalidator_test.go
index e441db00..17958a24 100644
--- a/internal/idtokenvalidator/idtokenvalidator_test.go
+++ b/internal/idtokenvalidator/idtokenvalidator_test.go
@@ -134,13 +134,13 @@ func TestIDTokenValidation(t *testing.T) {
 		token, err := builder.Build()
 		assert.NoError(t, err)
 
-		jwt, err := jwt.Sign(token, jwt.WithKey(jwa.HS512, []byte(jwtClientSecret)))
+		jwtPayload, err := jwt.Sign(token, jwt.WithKey(jwa.HS512, []byte(jwtClientSecret)))
 		assert.NoError(t, err)
 
 		validator, err := New(context.Background(), jwtDomain, jwtClientSecret, jwtClientID, "HS256")
 		assert.NoError(t, err)
 
-		err = validator.Validate(string(jwt), ValidationOptions{})
+		err = validator.Validate(string(jwtPayload), ValidationOptions{})
 		assert.ErrorContains(t, err, "signature algorithm \"HS512\" is not supported")
 	})
 
@@ -650,7 +650,9 @@ func configureSigning(t *testing.T, args jwtArgs) (jwa.SignatureAlgorithm, jwk.K
 			return
 		}
 		w.WriteHeader(http.StatusOK)
-		fmt.Fprintf(w, `{"keys": [%s] }`, b)
+		if _, err := fmt.Fprintf(w, `{"keys": [%s] }`, b); err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+		}
 	})
 	s := httptest.NewTLSServer(h)