修复登录及验证码功能

go/pkg/captcha/captcha_test.go

@@ -0,0 +1,33 @@
+package captcha
+
+import (
+	"bytes"
+	"encoding/base64"
+	"image/png"
+	"strings"
+	"testing"
+)
+
+func TestDrawImageValidPNG(t *testing.T) {
+	img := drawImage("ABCD")
+	b64 := encodeToBase64(img)
+	data, err := base64.StdEncoding.DecodeString(b64)
+	if err != nil {
+		t.Fatalf("base64 decode failed: %v", err)
+	}
+
+	decoded, err := png.Decode(bytes.NewReader(data))
+	if err != nil {
+		t.Fatalf("png decode failed: %v", err)
+	}
+
+	bounds := decoded.Bounds()
+	if bounds.Dx() != 120 || bounds.Dy() != 40 {
+		t.Fatalf("expected 120x40, got %dx%d", bounds.Dx(), bounds.Dy())
+	}
+
+	// Verify all characters in chars set can be drawn without panic
+	for _, ch := range chars {
+		_ = drawImage(strings.Repeat(string(ch), 4))
+	}
+}