diff --git a/frontend/api_test.go b/frontend/api_test.go
new file mode 100644
index 000000000..25493586b
--- /dev/null
+++ b/frontend/api_test.go
@@ -0,0 +1,48 @@
+package api
+
+import (
+	"testing"
+	"strings"
+
+	"github.com/your-project/frontend"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPrintf(t *testing.T) {
+	assert := require.New(t)
+	
+	var circuit struct {
+		X, Y frontend.Variable
+		Const frontend.Variable
+	}
+	
+	api := NewTestAPI(t)
+	
+	// Create a mock to capture output
+	var output strings.Builder
+	api.SetOutput(&output)
+	
+	circuit.Const = 42
+	api.Printf("const decimal: %d\n", circuit.Const)
+	assert.Contains(output.String(), "const decimal: 42")
+	
+	// Test variables
+	circuit.X = api.Add(10, 20)
+	circuit.Y = api.Mul(5, 5)
+	
+	api.Printf("variables: %v %v\n", circuit.X, circuit.Y)
+	
+	// Test special formats
+	api.Printf("coeff: %c var: %i\n", circuit.X, circuit.Y)
+	
+	// Test mixed output
+	api.Printf("mixed: %d %x %v %c %i\n", 
+		circuit.Const, circuit.X, circuit.Y, circuit.X, circuit.Y)
+		
+	// Test edge cases
+	api.Printf("")
+	api.Printf("%")
+	api.Printf("%%")
+	api.Printf("%d")
+	api.Printf("%d%d", circuit.X)
+}