make changes as per the doc

cmd/adapter/metrics_integration_test.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"context"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/beckn-one/beckn-onix/pkg/telemetry"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMetricsEndpointExposesPrometheus(t *testing.T) {
+	ctx := context.Background()
+	provider, err := telemetry.NewProvider(ctx, &telemetry.Config{
+		ServiceName:    "test-onix",
+		ServiceVersion: "1.0.0",
+		EnableMetrics:  true,
+		Environment:    "test",
+	})
+	require.NoError(t, err)
+	defer provider.Shutdown(context.Background())
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest("GET", "/metrics", nil)
+	provider.MetricsHandler.ServeHTTP(rec, req)
+
+	require.Equal(t, 200, rec.Code)
+	body := rec.Body.String()
+	require.Contains(t, body, "# HELP")
+	require.Contains(t, body, "# TYPE")
+}