test: cover explicit certificate font path

pkg/zxchainsdk/certificate_test.go

@@ -0,0 +1,73 @@
+package zxchainsdk
+
+import (
+	"bytes"
+	"context"
+	"image/color"
+	"image/png"
+	"testing"
+
+	"github.com/fogleman/gg"
+)
+
+func TestGenerateHashCertificateWithExplicitFontPath(t *testing.T) {
+	fontPath := firstAvailableTestFont(t)
+
+	result, err := GenerateHashCertificate(context.Background(), HashCertificateRequest{
+		Title:            "数字作品区块链存证证明",
+		CertNo:           "2026051315081710006",
+		UserName:         "测试用户",
+		UserID:           "10006",
+		WorkName:         "测试作品",
+		TaskID:           "task-10006",
+		CompletedAt:      "2026.05.13 15:08:17",
+		EvidenceID:       "ev-test",
+		TxID:             "tx-test",
+		BlockHeight:      "123456",
+		FinalHash:        "final-hash-test",
+		EvidenceHash:     "evidence-hash-test",
+		TrustedAt:        "2026.05.13 15:08:17",
+		VerifyURL:        "https://example.com/certificates/ev-test/certificate.png",
+		WorkPreviewBytes: solidPNG(t, 120, 80, color.RGBA{R: 0x33, G: 0x66, B: 0xcc, A: 0xff}),
+		BackgroundBytes:  solidPNG(t, 1369, 1920, color.RGBA{R: 0xff, G: 0xfd, B: 0xf8, A: 0xff}),
+		LogoBytes:        solidPNG(t, 304, 60, color.RGBA{R: 0x11, G: 0x11, B: 0x11, A: 0xff}),
+		FontPath:         fontPath,
+		BucketBaseURL:    "https://example.com",
+	})
+	if err != nil {
+		t.Fatalf("GenerateHashCertificate() error = %v", err)
+	}
+	if len(result.PNG) == 0 {
+		t.Fatal("GenerateHashCertificate() returned empty PNG")
+	}
+	if _, err := png.Decode(bytes.NewReader(result.PNG)); err != nil {
+		t.Fatalf("generated certificate is not a valid PNG: %v", err)
+	}
+}
+
+func firstAvailableTestFont(t *testing.T) string {
+	t.Helper()
+
+	for _, candidate := range certificateFontCandidates() {
+		if _, err := validateCertificateFont(candidate); err == nil {
+			return candidate
+		}
+	}
+	t.Skip("no loadable certificate font installed")
+	return ""
+}
+
+func solidPNG(t *testing.T, width, height int, c color.Color) []byte {
+	t.Helper()
+
+	dc := gg.NewContext(width, height)
+	dc.SetColor(c)
+	dc.DrawRectangle(0, 0, float64(width), float64(height))
+	dc.Fill()
+
+	var buf bytes.Buffer
+	if err := png.Encode(&buf, dc.Image()); err != nil {
+		t.Fatalf("encode test PNG: %v", err)
+	}
+	return buf.Bytes()
+}