test: make agent and systemd fixtures portable (#2461)

agent/gpu_fixture_test.go

@@ -0,0 +1,85 @@
+//go:build testing
+
+package agent
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// Run a copy of the test binary as a GPU command so fixtures do not need a shell.
+func TestMain(m *testing.M) {
+	executable, err := os.Executable()
+	if err != nil {
+		panic(err)
+	}
+	switch strings.TrimSuffix(filepath.Base(executable), ".exe") {
+	case nvidiaSmiCmd, rocmSmiCmd, tegraStatsCmd, nvtopCmd, intelGpuStatsCmd:
+		output, err := os.ReadFile(executable + ".stdout")
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+		// Only the parent creates files; a late collector must not undo cleanup.
+		args, err := os.OpenFile(executable+".args", os.O_WRONLY|os.O_TRUNC, 0)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+		_, err = io.WriteString(args, strings.Join(os.Args[1:], " "))
+		closeErr := args.Close()
+		if err == nil {
+			err = closeErr
+		}
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+		fmt.Print(string(output))
+		os.Exit(0)
+	}
+	os.Exit(m.Run())
+}
+
+func gpuCommandFixture(t *testing.T, dir, name, output string) string {
+	t.Helper()
+	executable, err := os.Executable()
+	require.NoError(t, err)
+	if runtime.GOOS == "windows" {
+		name += ".exe"
+	}
+	path := filepath.Join(dir, name)
+	if err := os.Link(executable, path); err != nil {
+		src, err := os.Open(executable)
+		require.NoError(t, err)
+		defer src.Close()
+		dst, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_EXCL, 0755)
+		require.NoError(t, err)
+		_, err = io.Copy(dst, src)
+		closeErr := dst.Close()
+		require.NoError(t, err)
+		require.NoError(t, closeErr)
+	}
+	require.NoError(t, os.WriteFile(path+".stdout", []byte(output), 0600))
+	require.NoError(t, os.WriteFile(path+".args", nil, 0600))
+	return path + ".args"
+}
+
+func TestGPUFixtureDoesNotRecreateRemovedArgs(t *testing.T) {
+	argsFile := gpuCommandFixture(t, t.TempDir(), nvidiaSmiCmd, "fixture output\n")
+	require.NoError(t, os.WriteFile(argsFile, nil, 0600))
+	require.NoError(t, os.Remove(argsFile))
+
+	cmd := exec.Command(strings.TrimSuffix(argsFile, ".args"))
+	err := cmd.Run()
+	require.NoFileExists(t, argsFile, "a late fixture process must not recreate files removed by cleanup")
+	require.Error(t, err, "the fixture must report a missing argument-capture file")
+}