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

controller/channel_test_internal_test.go

@@ -0,0 +1,71 @@
+package controller
+
+import (
+	"net/http/httptest"
+	"testing"
+
+	"github.com/QuantumNous/new-api/common"
+	"github.com/QuantumNous/new-api/dto"
+	"github.com/QuantumNous/new-api/pkg/billingexpr"
+	relaycommon "github.com/QuantumNous/new-api/relay/common"
+	"github.com/QuantumNous/new-api/types"
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSettleTestQuotaUsesTieredBilling(t *testing.T) {
+	info := &relaycommon.RelayInfo{
+		TieredBillingSnapshot: &billingexpr.BillingSnapshot{
+			BillingMode:   "tiered_expr",
+			ExprString:    `param("stream") == true ? tier("stream", p * 3) : tier("base", p * 2)`,
+			ExprHash:      billingexpr.ExprHashString(`param("stream") == true ? tier("stream", p * 3) : tier("base", p * 2)`),
+			GroupRatio:    1,
+			EstimatedTier: "stream",
+			QuotaPerUnit:  common.QuotaPerUnit,
+			ExprVersion:   1,
+		},
+		BillingRequestInput: &billingexpr.RequestInput{
+			Body: []byte(`{"stream":true}`),
+		},
+	}
+
+	quota, result := settleTestQuota(info, types.PriceData{
+		ModelRatio:      1,
+		CompletionRatio: 2,
+	}, &dto.Usage{
+		PromptTokens: 1000,
+	})
+
+	require.Equal(t, 1500, quota)
+	require.NotNil(t, result)
+	require.Equal(t, "stream", result.MatchedTier)
+}
+
+func TestBuildTestLogOtherInjectsTieredInfo(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	ctx, _ := gin.CreateTestContext(httptest.NewRecorder())
+
+	info := &relaycommon.RelayInfo{
+		TieredBillingSnapshot: &billingexpr.BillingSnapshot{
+			BillingMode: "tiered_expr",
+			ExprString:  `tier("base", p * 2)`,
+		},
+		ChannelMeta: &relaycommon.ChannelMeta{},
+	}
+	priceData := types.PriceData{
+		GroupRatioInfo: types.GroupRatioInfo{GroupRatio: 1},
+	}
+	usage := &dto.Usage{
+		PromptTokensDetails: dto.InputTokenDetails{
+			CachedTokens: 12,
+		},
+	}
+
+	other := buildTestLogOther(ctx, info, priceData, usage, &billingexpr.TieredResult{
+		MatchedTier: "base",
+	})
+
+	require.Equal(t, "tiered_expr", other["billing_mode"])
+	require.Equal(t, "base", other["matched_tier"])
+	require.NotEmpty(t, other["expr_b64"])
+}