diff --git a/mux_test.go b/mux_test.go
index bac758bc..a1ce7f10 100644
--- a/mux_test.go
+++ b/mux_test.go
@@ -2546,13 +2546,13 @@ func TestMethodsSubrouterPathVariable(t *testing.T) {
 	}
 }
 
-func ExampleSetURLVars() {
+func TestExampleSetURLVars(t *testing.T) {
 	req, _ := http.NewRequest("GET", "/foo", nil)
-	req = SetURLVars(req, map[string]string{"foo": "bar"})
+	req = SetURLVars(t, req, map[string]string{"foo": "bar"})
 
-	fmt.Println(Vars(req)["foo"])
-
-	// Output: bar
+	if val := Vars(req)["foo"]; val != "bar" {
+		t.Errorf("Expected URL var 'foo' to be 'bar', but got %q", val)
+	}
 }
 
 // testMethodsSubrouter runs an individual methodsSubrouterTest.
diff --git a/test_helpers.go b/test_helpers.go
index 5f5c496d..73e883b0 100644
--- a/test_helpers.go
+++ b/test_helpers.go
@@ -4,7 +4,10 @@
 
 package mux
 
-import "net/http"
+import (
+	"net/http"
+	"testing"
+)
 
 // SetURLVars sets the URL variables for the given request, to be accessed via
 // mux.Vars for testing route behaviour. Arguments are not modified, a shallow
@@ -14,6 +17,7 @@ import "net/http"
 // inject variables into the request context. Alternatively, URL variables
 // can be set by making a route that captures the required variables,
 // starting a server and sending the request to that server.
-func SetURLVars(r *http.Request, val map[string]string) *http.Request {
+func SetURLVars(t *testing.T, r *http.Request, val map[string]string) *http.Request {
+	t.Helper()
 	return requestWithVars(r, val)
 }