Cache repeated query translation and expansion

backend/services/gemini_test.go

@@ -88,3 +88,29 @@ func TestGeminiVisualCacheRoundTrip(t *testing.T) {
 		t.Fatalf("unexpected cached visual data: %q %q", data, mimeType)
 	}
 }
+
+func TestGeminiTranslationCacheRoundTrip(t *testing.T) {
+	service := NewGeminiService("")
+	service.setCachedTranslation("비 오는 도시", "rainy city", time.Minute)
+
+	value, ok := service.getCachedTranslation("비 오는 도시")
+	if !ok {
+		t.Fatal("expected translation cache hit")
+	}
+	if value != "rainy city" {
+		t.Fatalf("unexpected translation cache value: %q", value)
+	}
+}
+
+func TestGeminiExpansionCacheRoundTrip(t *testing.T) {
+	service := NewGeminiService("")
+	service.setCachedExpansion("city rain", []string{"city rain", "city rain stock footage"}, time.Minute)
+
+	value, ok := service.getCachedExpansion("city rain")
+	if !ok {
+		t.Fatal("expected expansion cache hit")
+	}
+	if len(value) != 2 || value[1] != "city rain stock footage" {
+		t.Fatalf("unexpected expansion cache value: %#v", value)
+	}
+}