test: add unit tests for internal/metrics

Add 14 tests covering:
- RecordAlertFired, RecordAlertResolved, RecordAlertAcknowledged
- RecordNotificationSent with success/failure
- RecordNotificationRetry, RecordNotificationDLQ
- RecordGroupedNotification with various counts
- RecordAlertEscalation with various levels
- RecordAlertSuppressed with various reasons
- UpdateQueueDepth, UpdateHistorySize
- RecordHistorySaveError
- Metric vector initialization verification

internal/metrics/alert_metrics_test.go

@@ -0,0 +1,154 @@
+package metrics
+
+import (
+	"testing"
+	"time"
+
+	"github.com/rcourtman/pulse-go-rewrite/internal/alerts"
+)
+
+func TestRecordAlertFired(t *testing.T) {
+	alert := &alerts.Alert{
+		ID:        "test-alert-1",
+		Level:     alerts.AlertLevelWarning,
+		Type:      "container_cpu",
+		StartTime: time.Now(),
+	}
+
+	// Should not panic
+	RecordAlertFired(alert)
+}
+
+func TestRecordAlertResolved(t *testing.T) {
+	now := time.Now()
+	alert := &alerts.Alert{
+		ID:        "test-alert-2",
+		Level:     alerts.AlertLevelWarning,
+		Type:      "container_memory",
+		StartTime: now.Add(-5 * time.Minute),
+		LastSeen:  now,
+	}
+
+	// Should not panic
+	RecordAlertResolved(alert)
+}
+
+func TestRecordAlertAcknowledged(t *testing.T) {
+	// Should not panic
+	RecordAlertAcknowledged()
+}
+
+func TestRecordNotificationSent_Success(t *testing.T) {
+	// Should not panic
+	RecordNotificationSent("email", true)
+}
+
+func TestRecordNotificationSent_Failure(t *testing.T) {
+	// Should not panic
+	RecordNotificationSent("webhook", false)
+}
+
+func TestRecordNotificationRetry(t *testing.T) {
+	// Should not panic
+	RecordNotificationRetry("email")
+}
+
+func TestRecordNotificationDLQ(t *testing.T) {
+	// Should not panic
+	RecordNotificationDLQ()
+}
+
+func TestRecordGroupedNotification(t *testing.T) {
+	// Should not panic with various counts
+	RecordGroupedNotification(1)
+	RecordGroupedNotification(5)
+	RecordGroupedNotification(50)
+}
+
+func TestRecordAlertEscalation(t *testing.T) {
+	// Should not panic with various levels
+	RecordAlertEscalation(1)
+	RecordAlertEscalation(2)
+	RecordAlertEscalation(3)
+}
+
+func TestRecordAlertSuppressed(t *testing.T) {
+	// Should not panic with various reasons
+	RecordAlertSuppressed("quiet_hours")
+	RecordAlertSuppressed("rate_limit")
+	RecordAlertSuppressed("duplicate")
+}
+
+func TestUpdateQueueDepth(t *testing.T) {
+	// Should not panic with various statuses and counts
+	UpdateQueueDepth("pending", 10)
+	UpdateQueueDepth("sending", 5)
+	UpdateQueueDepth("dlq", 0)
+}
+
+func TestUpdateHistorySize(t *testing.T) {
+	// Should not panic with various sizes
+	UpdateHistorySize(0)
+	UpdateHistorySize(100)
+	UpdateHistorySize(1000)
+}
+
+func TestRecordHistorySaveError(t *testing.T) {
+	// Should not panic
+	RecordHistorySaveError()
+}
+
+func TestMetricVectors_NotNil(t *testing.T) {
+	// Verify that metric vectors are properly initialized
+	if AlertsActive == nil {
+		t.Error("AlertsActive should not be nil")
+	}
+	if AlertsFiredTotal == nil {
+		t.Error("AlertsFiredTotal should not be nil")
+	}
+	if AlertsResolvedTotal == nil {
+		t.Error("AlertsResolvedTotal should not be nil")
+	}
+	if AlertsAcknowledgedTotal == nil {
+		t.Error("AlertsAcknowledgedTotal should not be nil")
+	}
+	if AlertDurationSeconds == nil {
+		t.Error("AlertDurationSeconds should not be nil")
+	}
+	if NotificationsSentTotal == nil {
+		t.Error("NotificationsSentTotal should not be nil")
+	}
+	if NotificationQueueDepth == nil {
+		t.Error("NotificationQueueDepth should not be nil")
+	}
+	if NotificationDeliveryDuration == nil {
+		t.Error("NotificationDeliveryDuration should not be nil")
+	}
+	if NotificationRetriesTotal == nil {
+		t.Error("NotificationRetriesTotal should not be nil")
+	}
+	if NotificationDLQTotal == nil {
+		t.Error("NotificationDLQTotal should not be nil")
+	}
+	if NotificationsGroupedTotal == nil {
+		t.Error("NotificationsGroupedTotal should not be nil")
+	}
+	if AlertsGroupedCount == nil {
+		t.Error("AlertsGroupedCount should not be nil")
+	}
+	if AlertEscalationsTotal == nil {
+		t.Error("AlertEscalationsTotal should not be nil")
+	}
+	if AlertHistorySize == nil {
+		t.Error("AlertHistorySize should not be nil")
+	}
+	if AlertHistorySaveErrors == nil {
+		t.Error("AlertHistorySaveErrors should not be nil")
+	}
+	if AlertsSuppressedTotal == nil {
+		t.Error("AlertsSuppressedTotal should not be nil")
+	}
+	if AlertsRateLimitedTotal == nil {
+		t.Error("AlertsRateLimitedTotal should not be nil")
+	}
+}