mock-hdiutil-testing

name	mock-hdiutil-testing
description	Write and run isolated unit tests for mkdmg using mock executors and simulation modes. Use this skill when testing CLI logic, configuration validation, or runner workflows without invoking real macOS hdiutil commands.

Mock HDIUtil Testing Guide

This skill provides patterns and instructions for testing mkdmg in environments where real macOS disk mounting / hdiutil commands cannot or should not be executed (such as restricted sandboxes, CI Linux containers, or developer machines without root privileges).

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1. Simulation Flag Mode (-s / --dry-run)

When testing run() in main_test.go, always ensure that -s or --dry-run is included in os.Args:

func TestCLIWithSimulation(t *testing.T) {
    sourceDir := t.TempDir()
    outputDMG := filepath.Join(t.TempDir(), "test.dmg")
    cfgFile := writeConfigFile(t, map[string]any{
        "output_path": outputDMG,
        "source_dir":  sourceDir,
    })
    
    // Pass -s to ensure Runner.SetSimulate(true) is activated
    resetForTest(t, []string{"mkdmg", "-s", "--config", cfgFile})
    
    err := run()
    if err != nil {
        t.Fatalf("run() failed: %v", err)
    }
}

---

2. Using CommandExecutor Mocks

For unit tests targeting al.essio.dev/pkg/hdiutil, use the mock executor pattern:

type mockExecutor struct {
    calls []string
}

func (m *mockExecutor) Hdiutil(args ...string) ([]byte, error) {
    m.calls = append(m.calls, "hdiutil "+strings.Join(args, " "))
    return []byte("created"), nil
}

func (m *mockExecutor) Codesign(args ...string) ([]byte, error) {
    m.calls = append(m.calls, "codesign "+strings.Join(args, " "))
    return nil, nil
}

func (m *mockExecutor) Xcrun(args ...string) ([]byte, error) {
    m.calls = append(m.calls, "xcrun "+strings.Join(args, " "))
    return nil, nil
}

func (m *mockExecutor) Chmod(args ...string) error {
    return nil
}

func (m *mockExecutor) Bless(args ...string) error {
    return nil
}

Inject the mock executor via hdiutil.WithExecutor:

runner := hdiutil.New(cfg, hdiutil.WithExecutor(mock))

---

3. Hermetic Test Guidelines

1. Temporary Directories: Always use t.TempDir() for temporary source files and DMG output targets.
2. State Reset: Always restore global state (flag.CommandLine, os.Args, global flags) with t.Cleanup().
3. No Network / No Disk Mounts: Verify that tests run successfully offline and without disk attachment.