# I open sourced testvm, so your coding agents can test Mac apps in a VM

> testvm is my free, open source tool that runs Mac app builds in a headless macOS VM, so coding agents test them without taking over your screen.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2026-10-06 | Topics: [News](https://flaviocopes.com/tags/news/) | Canonical: https://flaviocopes.com/testvm/

I open sourced `testvm`, the script my coding agents use to test the Mac apps they build. It runs each build in a headless macOS virtual machine, so the agents can open it, take screenshots and click through it while I keep working on my screen.

It's free and MIT licensed, on GitHub at [flaviocopes/testvm](https://github.com/flaviocopes/testvm).

![Skillscout running on the screen of the macOS test VM](https://flaviocopes.com/images/mac-test-vm/skillscout-in-vm.png)

I explained how the VM works, step by step, in [How to let coding agents test Mac apps in a VM](https://flaviocopes.com/mac-test-vm/). `testvm` is what I ended up with after typing those `ssh` commands one time too many.

Until today it lived inside the repo of [VM Monitor](https://flaviocopes.com/vm-monitor/), my app that shows what agents do in the VM. Now it has its own repo, so you can use it without VM Monitor.

## What it does

An agent builds the app on my Mac as usual, then tests it in the VM:

```bash
testvm open build/Build/Products/Debug/Skillscout.app
testvm shot Skillscout
testvm ui Skillscout
testvm click 1171 114
```

`open` copies the app into the VM and launches it. `shot` takes a screenshot of its window. `ui` lists the window's controls with their labels and the point to click, so the agent doesn't have to guess from pixels. Then `click`, `type` and `key` interact with the app.

The VM runs under [Tart](https://tart.run) with no window and no Dock icon, so nothing shows up on my screen. When it's off, `testvm` starts it.

Every command also goes into a log, with the agent that ran it (Cursor, Claude Code or Codex) and its chat. That's the log VM Monitor reads.

## What's new in 1.1

Moving it to its own repo was a good moment to clean it up for people who aren't me:

- The VM's image, cores, memory and display size are now settings in `~/.config/testvm/config`. Before, they were fixed in the script.
- `testvm` can drive a real Mac instead of the VM, like a Mac mini on your network. It now checks that Mac's SSH host key, and it finds cliclick on an Intel Mac mini too.
- The repo has a skill that teaches your agents every `testvm` command.

## Try it

You need an Apple silicon Mac with Tart installed. Then download `testvm` and create the VM:

```bash
curl -Lo /opt/homebrew/bin/testvm https://github.com/flaviocopes/testvm/releases/latest/download/testvm
chmod +x /opt/homebrew/bin/testvm
testvm setup
```

`setup` downloads Cirrus Labs' macOS Sequoia image, which is about 25 GB, so give it a while.

Then install the skill, so your agents know how to use `testvm`:

```bash
npx skills add flaviocopes/testvm
```

The [README](https://github.com/flaviocopes/testvm#tell-your-agents-to-use-it) has the rule I give my agents so they stop opening apps on my Mac, the settings, and how to point `testvm` at a Mac mini.