test(backend): add unit tests for auth_middleware, fortee, processor, account, and more handlers

Cover previously untested code: SessionCookieMiddleware, context helpers,
downloadFile, addAcceptHeader, doProcessTaskRunTestcase, updateSubmissionAndGameState,
PostLogout, GetGames, PostGamePlayCode, GetGameWatchRanking, GetGameWatchLatestStates.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 94 insertions, 0 deletions

diff --git a/backend/account/icon_test.go b/backend/account/icon_test.go
new file mode 100644
index 0000000..7f4ddbc
--- /dev/null
+++ b/backend/account/icon_test.go
@@ -0,0 +1,94 @@
+package account
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestDownloadFile_Success(t *testing.T) {
+	expectedContent := "file content here"
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte(expectedContent))
+	}))
+	defer server.Close()
+
+	tmpDir := t.TempDir()
+	filePath := filepath.Join(tmpDir, "subdir", "test.png")
+
+	err := downloadFile(context.Background(), server.URL+"/icon.png", filePath)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	data, err := os.ReadFile(filePath)
+	if err != nil {
+		t.Fatalf("failed to read downloaded file: %v", err)
+	}
+	if string(data) != expectedContent {
+		t.Errorf("expected content %q, got %q", expectedContent, string(data))
+	}
+}
+
+func TestDownloadFile_NotFound(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusNotFound)
+	}))
+	defer server.Close()
+
+	tmpDir := t.TempDir()
+	filePath := filepath.Join(tmpDir, "test.png")
+
+	err := downloadFile(context.Background(), server.URL+"/missing.png", filePath)
+	if err == nil {
+		t.Error("expected error for 404 response")
+	}
+}
+
+func TestDownloadFile_ServerError(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusInternalServerError)
+	}))
+	defer server.Close()
+
+	tmpDir := t.TempDir()
+	filePath := filepath.Join(tmpDir, "test.png")
+
+	err := downloadFile(context.Background(), server.URL+"/error.png", filePath)
+	if err == nil {
+		t.Error("expected error for 500 response")
+	}
+}
+
+func TestDownloadFile_InvalidURL(t *testing.T) {
+	tmpDir := t.TempDir()
+	filePath := filepath.Join(tmpDir, "test.png")
+
+	err := downloadFile(context.Background(), "http://localhost:1/unreachable", filePath)
+	if err == nil {
+		t.Error("expected error for unreachable server")
+	}
+}
+
+func TestDownloadFile_ContextCanceled(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte("data"))
+	}))
+	defer server.Close()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel() // cancel immediately
+
+	tmpDir := t.TempDir()
+	filePath := filepath.Join(tmpDir, "test.png")
+
+	err := downloadFile(ctx, server.URL+"/icon.png", filePath)
+	if err == nil {
+		t.Error("expected error for canceled context")
+	}
+}