CosmicClash/server/observability/metrics_test.go

package observability

import (
	"strings"
	"testing"
	"time"
)

func TestMetricsNormalizesOperationsAndExportsBoundedLabels(t *testing.T) {
	m := NewMetrics()
	m.ObserveAPI("queue", 201, 10*time.Millisecond)
	m.ObserveAPI("/crafted/path/with-secret", 500, time.Second)
	var output strings.Builder
	if err := m.WritePrometheus(&output); err != nil {
		t.Fatal(err)
	}
	text := output.String()
	if !strings.Contains(text, `operation="queue",status="2xx"`) || !strings.Contains(text, `operation="other",status="5xx"`) {
		t.Fatalf("metrics output = %s", text)
	}
	if !strings.Contains(text, "# TYPE cosmic_clash_api_latency_seconds histogram") ||
		!strings.Contains(text, `cosmic_clash_api_latency_seconds_bucket{operation="queue",status="2xx",le="0.25"} 1`) ||
		!strings.Contains(text, `cosmic_clash_api_latency_seconds_bucket{operation="queue",status="2xx",le="+Inf"} 1`) {
		t.Fatalf("latency histogram missing expected buckets: %s", text)
	}
	if strings.Contains(text, "crafted") || strings.Contains(text, "secret") {
		t.Fatalf("unbounded operation label leaked: %s", text)
	}
}

func TestMetricsHistogramUsesCumulativeBoundarySemantics(t *testing.T) {
	m := NewMetrics()
	m.ObserveAPI("queue", 200, 250*time.Millisecond)
	var output strings.Builder
	if err := m.WritePrometheus(&output); err != nil {
		t.Fatal(err)
	}
	text := output.String()
	if !strings.Contains(text, `le="0.25"} 1`) || !strings.Contains(text, `le="0.5"} 1`) {
		t.Fatalf("boundary observation was not cumulative: %s", text)
	}
	if strings.Contains(text, `le="0.1"} 1`) {
		t.Fatalf("250ms observation entered an earlier bucket: %s", text)
	}
}