feat(knowledge): 图片上传接口（S3 存储，限 5MB jpg/png/webp）

server-go/internal/handler/knowledge_image_test.go

@@ -0,0 +1,66 @@
+package handler
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestValidateImageFileRejectsOversize(t *testing.T) {
+	if err := validateImageFile("a.png", maxImageSize+1); err == nil {
+		t.Error("超过 5MB 的图片应被拒绝")
+	}
+}
+
+func TestValidateImageFileRejectsEmptyAndBadExt(t *testing.T) {
+	if err := validateImageFile("a.png", 0); err == nil {
+		t.Error("空文件应被拒绝")
+	}
+	if err := validateImageFile("a.txt", 1024); err == nil {
+		t.Error("非图片扩展名应被拒绝")
+	}
+}
+
+func TestValidateImageFileAcceptsAllowed(t *testing.T) {
+	for _, name := range []string{"a.jpg", "a.jpeg", "a.png", "a.webp"} {
+		if err := validateImageFile(name, 1024); err != nil {
+			t.Errorf("%s 应被允许: %v", name, err)
+		}
+	}
+}
+
+func TestImageContentType(t *testing.T) {
+	cases := map[string]string{
+		".jpg":  "image/jpeg",
+		".jpeg": "image/jpeg",
+		".png":  "image/png",
+		".webp": "image/webp",
+	}
+	for ext, want := range cases {
+		got, ok := imageContentType(ext)
+		if !ok || got != want {
+			t.Errorf("imageContentType(%s) = %q, %v; want %q", ext, got, ok, want)
+		}
+	}
+	if _, ok := imageContentType(".gif"); ok {
+		t.Error(".gif 不应被支持")
+	}
+}
+
+func TestBuildImageKey(t *testing.T) {
+	key, ext, err := buildImageKey("病蚕照片.PNG")
+	if err != nil {
+		t.Fatalf("buildImageKey 失败: %v", err)
+	}
+	if !strings.HasPrefix(key, "knowledge/") {
+		t.Errorf("key 应以 knowledge/ 开头: %s", key)
+	}
+	if !strings.HasSuffix(key, ".png") {
+		t.Errorf("key 应以 .png 结尾: %s", key)
+	}
+	if ext != ".png" {
+		t.Errorf("ext = %s, want .png", ext)
+	}
+	if len(key) <= len("knowledge/")+8 {
+		t.Errorf("key 应包含日期与随机部分: %s", key)
+	}
+}