fix(channel-test): support tiered billing model tests (#4145)

Pre-fill BillingRequestInput from dto.Request before ModelPriceHelper,
so tiered_expr billing resolves param() from the structured request
instead of reading HTTP body (which is empty in channel-test context).

- attachTestBillingRequestInput: marshal dto.Request → RequestInput
- ResolveIncomingBillingExprRequestInput: early-return when pre-filled
- settleTestQuota / buildTestLogOther: align test settlement & logging
  with production TryTieredSettle / InjectTieredBillingInfo paths

relay/helper/price_test.go

@@ -0,0 +1,62 @@
+package helper
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/QuantumNous/new-api/common"
+	"github.com/QuantumNous/new-api/pkg/billingexpr"
+	relaycommon "github.com/QuantumNous/new-api/relay/common"
+	"github.com/QuantumNous/new-api/setting/billing_setting"
+	"github.com/QuantumNous/new-api/setting/config"
+	"github.com/QuantumNous/new-api/types"
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/require"
+)
+
+func TestModelPriceHelperTieredUsesPreloadedRequestInput(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	saved := map[string]string{}
+	require.NoError(t, config.GlobalConfig.SaveToDB(func(key, value string) error {
+		saved[key] = value
+		return nil
+	}))
+	t.Cleanup(func() {
+		require.NoError(t, config.GlobalConfig.LoadFromDB(saved))
+	})
+
+	require.NoError(t, config.GlobalConfig.LoadFromDB(map[string]string{
+		"billing_setting.billing_mode": `{"tiered-test-model":"tiered_expr"}`,
+		"billing_setting.billing_expr": `{"tiered-test-model":"param(\"stream\") == true ? tier(\"stream\", p * 3) : tier(\"base\", p * 2)"}`,
+	}))
+
+	recorder := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(recorder)
+	req := httptest.NewRequest(http.MethodPost, "/api/channel/test/1", nil)
+	req.Body = nil
+	req.ContentLength = 0
+	req.Header.Set("Content-Type", "application/json")
+	ctx.Request = req
+	ctx.Set("group", "default")
+
+	info := &relaycommon.RelayInfo{
+		OriginModelName: "tiered-test-model",
+		UserGroup:       "default",
+		UsingGroup:      "default",
+		RequestHeaders:  map[string]string{"Content-Type": "application/json"},
+		BillingRequestInput: &billingexpr.RequestInput{
+			Headers: map[string]string{"Content-Type": "application/json"},
+			Body:    []byte(`{"stream":true}`),
+		},
+	}
+
+	priceData, err := ModelPriceHelper(ctx, info, 1000, &types.TokenCountMeta{})
+	require.NoError(t, err)
+	require.Equal(t, 1500, priceData.QuotaToPreConsume)
+	require.NotNil(t, info.TieredBillingSnapshot)
+	require.Equal(t, "stream", info.TieredBillingSnapshot.EstimatedTier)
+	require.Equal(t, billing_setting.BillingModeTieredExpr, info.TieredBillingSnapshot.BillingMode)
+	require.Equal(t, common.QuotaPerUnit, info.TieredBillingSnapshot.QuotaPerUnit)
+}