feat: ground competitive insights in peer metrics

internal/peercomparison/calculator_test.go

@@ -0,0 +1,76 @@
+package peercomparison
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+func pointer(value float64) *float64 { return &value }
+
+func TestCalculateAppliesPrivacyThresholdsAndExcludesActiveMerchant(t *testing.T) {
+	merchants := make([]MerchantValues, 0, 11)
+	merchants = append(merchants, MerchantValues{MerchantID: 70, SessionCount: 900, Values: [8]*float64{pointer(0)}})
+	for i := int64(1); i <= 10; i++ {
+		merchants = append(merchants, MerchantValues{MerchantID: i, SessionCount: 100, Values: [8]*float64{pointer(float64(i))}})
+	}
+	result := Calculate(70, false, merchants)
+	if result.State != StateReady || result.EligiblePeerCount != 10 || result.CombinedPeerSessions != 1000 {
+		t.Fatalf("unexpected ready result: %+v", result)
+	}
+	if result.Metrics[0].MerchantPerformancePercentile != "0.00" {
+		t.Fatalf("active merchant must be ranked below all peers: %+v", result.Metrics[0])
+	}
+	suppressed := Calculate(70, true, merchants)
+	if suppressed.State != StateSuppressed || suppressed.Reason != "TERMINAL_SCOPE_UNSUPPORTED" {
+		t.Fatalf("unexpected terminal result: %+v", suppressed)
+	}
+	insufficient := Calculate(70, false, merchants[:10])
+	if insufficient.State != StateSuppressed || insufficient.Reason != "INSUFFICIENT_COHORT" {
+		t.Fatalf("unexpected insufficient result: %+v", insufficient)
+	}
+}
+
+func TestCalculateUsesDirectionAwareMidRankAndStableMetricOrder(t *testing.T) {
+	merchants := make([]MerchantValues, 0, 11)
+	merchants = append(merchants, MerchantValues{MerchantID: 70, SessionCount: 1, Values: [8]*float64{pointer(5), pointer(5), pointer(5), pointer(5), pointer(5), pointer(5), pointer(5), pointer(5)}})
+	for i := int64(1); i <= 10; i++ {
+		value := float64(i)
+		merchants = append(merchants, MerchantValues{MerchantID: i, SessionCount: 100, Values: [8]*float64{pointer(value), pointer(value), pointer(value), pointer(value), pointer(value), pointer(value), pointer(value), pointer(value)}})
+	}
+	result := Calculate(70, false, merchants)
+	if len(result.Metrics) != 8 || result.Metrics[0].MetricID != "payment_success_rate" || result.Metrics[7].MetricID != "paid_fee_rate" {
+		t.Fatalf("unexpected metric order: %+v", result.Metrics)
+	}
+	if result.Metrics[0].MerchantPerformancePercentile != "45.00" {
+		t.Fatalf("higher-is-better midrank = %s, want 45.00", result.Metrics[0].MerchantPerformancePercentile)
+	}
+	if result.Metrics[3].MerchantPerformancePercentile != "55.00" || result.Metrics[3].Direction != "LOWER_IS_BETTER" {
+		t.Fatalf("lower-is-better direction/percentile = %+v", result.Metrics[3])
+	}
+}
+
+func TestCalculateKeepsPeerIdentitiesOutOfSerializedResult(t *testing.T) {
+	merchants := []MerchantValues{{MerchantID: 987654321, Values: [8]*float64{pointer(5)}}}
+	for i := int64(1); i <= 10; i++ {
+		merchants = append(merchants, MerchantValues{
+			MerchantID:   1000 + i,
+			SessionCount: 100,
+			Values:       [8]*float64{pointer(5)},
+		})
+	}
+	result := Calculate(987654321, false, merchants)
+	encoded, err := json.Marshal(result)
+	if err != nil {
+		t.Fatalf("marshal result: %v", err)
+	}
+	text := string(encoded)
+	for _, forbidden := range []string{"merchantId", "987654321", "1001"} {
+		if strings.Contains(text, forbidden) {
+			t.Fatalf("serialized peer result exposed %q: %s", forbidden, text)
+		}
+	}
+	if result.Metrics[0].MerchantPerformancePercentile != "50.00" {
+		t.Fatalf("all-tie percentile = %s, want 50.00", result.Metrics[0].MerchantPerformancePercentile)
+	}
+}