test(agentcompat): add agent runtime harness

Co-authored-by: naiba/CloudCode <hi+cloudcode@nai.ba>

integration/agentcompat/internal/agent/failed_start_recovery_test.go

@@ -0,0 +1,68 @@
+//go:build linux && agentcompat
+
+package agent
+
+import (
+	"context"
+	"errors"
+	"syscall"
+	"testing"
+	"time"
+
+	processharness "github.com/nezhahq/nezha/integration/agentcompat/internal/process"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAgent_StartExposesFinalizerWhenPreparedConsumerSurvivesRollback(t *testing.T) {
+	prepared, err := PrepareBinary(t.Context(), testAgentSourceDir(t))
+	require.NoError(t, err)
+	trackingErr := errors.New("injected failed-start PID tracking error")
+	var supervisor *processharness.Supervisor
+
+	instance, startErr := Start(t.Context(), AgentStartConfig{
+		PreparedBinary: prepared,
+		Endpoint:       "127.0.0.1:1",
+		UUID:           "00000000-0000-0000-0000-000000000200",
+		newSupervisor: func(ctx context.Context, spec processharness.Spec) *processharness.Supervisor {
+			supervisor = processharness.NewSupervisor(ctx, spec)
+			cancelledContext, cancel := context.WithCancel(ctx)
+			cancel()
+			_ = supervisor.Stop(cancelledContext)
+			require.NoError(t, supervisor.Stop(t.Context()))
+			return supervisor
+		},
+		trackPID: func(int) error { return trackingErr },
+	})
+	require.Nil(t, instance)
+	require.ErrorIs(t, startErr, trackingErr)
+	require.NotNil(t, supervisor)
+	pid := supervisor.PID()
+	processGroupID := supervisor.ProcessGroupID()
+	t.Cleanup(func() {
+		_ = syscall.Kill(-processGroupID, syscall.SIGKILL)
+		select {
+		case <-supervisor.Exited():
+		case <-time.After(5 * time.Second):
+		}
+		_ = prepared.Close()
+	})
+	require.NoError(t, syscall.Kill(-processGroupID, 0))
+
+	var startFailure *AgentStartError
+	require.ErrorAs(t, startErr, &startFailure)
+	closeErr := prepared.Close()
+	var usageErr *PreparedBinaryUsageError
+	require.ErrorAs(t, closeErr, &usageErr)
+	require.Equal(t, "has active consumers", usageErr.Reason)
+
+	require.NoError(t, syscall.Kill(-processGroupID, syscall.SIGKILL))
+	select {
+	case <-supervisor.Exited():
+	case <-time.After(5 * time.Second):
+		t.Fatalf("failed-start consumer PID %d was not reaped", pid)
+	}
+	require.ErrorIs(t, syscall.Kill(-processGroupID, 0), syscall.ESRCH)
+	require.NoError(t, startFailure.Finalize(t.Context()))
+	require.NoError(t, startFailure.Finalize(t.Context()))
+	require.NoError(t, prepared.Close())
+}