test(routing): cover TTL expiry in fetcher

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

internal/routing/passrate_test.go

@@ -60,6 +60,27 @@ func TestFetcherCachesWithinTTL(t *testing.T) {
 	assert.Equal(t, int32(1), atomic.LoadInt32(&calls), "should hit upstream once and serve four times from cache")
 }
 
+func TestFetcherFetchesAgainAfterTTLExpires(t *testing.T) {
+	var calls int32
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		atomic.AddInt32(&calls, 1)
+		_ = json.NewEncoder(w).Encode(map[string]any{"pass_rate": 0.5})
+	}))
+	defer srv.Close()
+
+	// Tight TTL so the test stays fast.
+	f := routing.NewFetcher(srv.URL, "7d", 5*time.Millisecond)
+	_, err := f.Get(context.Background(), "tdd")
+	require.NoError(t, err)
+	assert.Equal(t, int32(1), atomic.LoadInt32(&calls))
+
+	// Sleep past TTL, then a second Get should hit upstream again.
+	time.Sleep(15 * time.Millisecond)
+	_, err = f.Get(context.Background(), "tdd")
+	require.NoError(t, err)
+	assert.Equal(t, int32(2), atomic.LoadInt32(&calls), "expected fresh upstream call after TTL expiry")
+}
+
 func TestFetcherSurfacesUpstreamError(t *testing.T) {
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 		http.Error(w, "boom", http.StatusInternalServerError)