fix(metrics): stabilize cpu and power sampling

audit/internal/platform/sat_fan_stress_test.go

@@ -1,6 +1,9 @@
 package platform
 
-import "testing"
+import (
+	"testing"
+	"time"
+)
 
 func TestParseFanSpeeds(t *testing.T) {
 	raw := "FAN1 | 2400.000 | RPM | ok\nFAN2 | 1800 RPM | ok | ok\nFAN3 | na | RPM | ns\n"
@@ -25,3 +28,40 @@ func TestFirstFanInputValue(t *testing.T) {
 		t.Fatalf("got=%v ok=%v", got, ok)
 	}
 }
+
+func TestParseDCMIPowerReading(t *testing.T) {
+	raw := `
+Instantaneous power reading:                   512 Watts
+Minimum during sampling period:               498 Watts
+`
+	if got := parseDCMIPowerReading(raw); got != 512 {
+		t.Fatalf("parseDCMIPowerReading()=%v want 512", got)
+	}
+}
+
+func TestEffectiveSystemPowerReading(t *testing.T) {
+	now := time.Now()
+	cache := cachedPowerReading{Value: 480, UpdatedAt: now.Add(-5 * time.Second)}
+
+	got, updated := effectiveSystemPowerReading(cache, 0, now)
+	if got != 480 {
+		t.Fatalf("got=%v want cached 480", got)
+	}
+	if updated.Value != 480 {
+		t.Fatalf("updated=%+v", updated)
+	}
+
+	got, updated = effectiveSystemPowerReading(cache, 530, now)
+	if got != 530 {
+		t.Fatalf("got=%v want 530", got)
+	}
+	if updated.Value != 530 {
+		t.Fatalf("updated=%+v", updated)
+	}
+
+	expired := cachedPowerReading{Value: 480, UpdatedAt: now.Add(-systemPowerHoldTTL - time.Second)}
+	got, _ = effectiveSystemPowerReading(expired, 0, now)
+	if got != 0 {
+		t.Fatalf("expired cache returned %v want 0", got)
+	}
+}