Add USB blackbox log mirroring service

audit/internal/app/blackbox_test.go

@@ -0,0 +1,52 @@
+package app
+
+import (
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+func TestAdjustFlushPeriodGrowsOnSlowCycle(t *testing.T) {
+	current := 2 * time.Second
+	got := adjustFlushPeriod(current, 4*time.Second, false, 0)
+	if got <= current {
+		t.Fatalf("adjustFlushPeriod=%s want > %s", got, current)
+	}
+}
+
+func TestAdjustFlushPeriodShrinksAfterFastCycles(t *testing.T) {
+	current := 10 * time.Second
+	got := adjustFlushPeriod(current, 2*time.Second, true, blackboxRecoveryFastCount)
+	if got >= current {
+		t.Fatalf("adjustFlushPeriod=%s want < %s", got, current)
+	}
+	if got < blackboxMinFlushPeriod {
+		t.Fatalf("adjustFlushPeriod=%s below min %s", got, blackboxMinFlushPeriod)
+	}
+}
+
+func TestReadBlackboxState(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "blackbox-state.json")
+	want := BlackboxState{
+		Status:           "running",
+		BootStartedAtUTC: "2026-04-24T00:00:00Z",
+		BootFolder:       "boot-folder",
+		UpdatedAtUTC:     "2026-04-24T00:00:01Z",
+		Targets: []BlackboxTargetStatus{{
+			EnrollmentID: "bb-1",
+			Device:       "/dev/sdb1",
+			Status:       "running",
+			FlushPeriod:  "1s",
+		}},
+	}
+	if err := writeJSONAtomic(path, want); err != nil {
+		t.Fatalf("writeJSONAtomic: %v", err)
+	}
+	got, err := ReadBlackboxState(path)
+	if err != nil {
+		t.Fatalf("ReadBlackboxState: %v", err)
+	}
+	if got.Status != want.Status || got.BootFolder != want.BootFolder || len(got.Targets) != 1 || got.Targets[0].EnrollmentID != "bb-1" {
+		t.Fatalf("state=%+v", got)
+	}
+}