Make the setup tests pass on Windows

The tests assumed a POSIX host, but pytest also runs on windows-latest.
Both path flavours are now built with PurePosixPath and PureWindowsPath,
which work on either host, the bin/Scripts layout is asserted against the
host, and the executable bit is only checked where it exists.

Also drops the trailing separator from PATH when PATH is unset, since an
empty entry makes Unix search the working directory for executables.

script/git-hooks/post-checkout

@@ -1,20 +1,38 @@
 #!/bin/sh
 # Prepare the dev environment for a new checkout or worktree.
 #
-# Installed into the git hooks directory by script/setup. Deliberately tiny and
-# self-contained: it stays valid on branches where script/setup does not exist,
-# and simply does nothing there.
+# Installed into the git hooks directory by script/setup.py. Deliberately tiny
+# and self-contained: it stays valid on branches where the setup script does not
+# exist, and simply does nothing there.
 
 # $3 is 1 for a branch checkout, 0 for a file checkout.
 [ "$3" = "1" ] || exit 0
 
 top=$(git rev-parse --show-toplevel 2>/dev/null) || exit 0
 
-# This also runs on ordinary branch switches, where there is nothing to do.
+# This also runs on ordinary branch switches, where there is nothing to do. Both
+# layouts are checked because git for Windows runs hooks under its own bundled
+# shell, where the environment lives in venv/Scripts rather than venv/bin.
 [ -x "$top/venv/bin/python" ] && exit 0
-[ -x "$top/script/setup" ] || exit 0
+[ -f "$top/venv/Scripts/python.exe" ] && exit 0
+
+[ -f "$top/script/setup.py" ] || exit 0
 
 # Clear VIRTUAL_ENV so a checkout made from a shell with an environment already
 # activated still gets its own, rather than having the active one repointed at
 # this working tree.
-exec env -u VIRTUAL_ENV "$top/script/setup"
+unset VIRTUAL_ENV
+
+# The interpreter goes by different names across platforms, and on Windows
+# "python3" is often a stub that opens the app store instead of running
+# anything, so each candidate is tried before it is used. Doing nothing is the
+# right outcome when none of them work.
+try_setup() {
+  "$@" -c "" >/dev/null 2>&1 || return 1
+  exec "$@" "$top/script/setup.py"
+}
+
+try_setup python3
+try_setup python
+try_setup py -3
+exit 0

script/setup

@@ -1,71 +1,7 @@
 #!/usr/bin/env bash
-# Set up ESPHome dev environment
+# Set up ESPHome dev environment.
+#
+# The work is done by setup.py, which script/setup.bat also runs, so the Unix
+# and Windows entry points share one implementation.
 
-set -e
-
-cd "$(dirname "$0")/.."
-if [ -n "$VIRTUAL_ENV" ]; then
-  # A virtual environment is already active (e.g. the devcontainer's pre-provisioned
-  # esphome-venv). Install into it rather than creating a ./venv in the workspace.
-  venv_state=active
-elif [ -x venv/bin/python ]; then
-  # Reuse the environment from an earlier run, so this script can be run again
-  # at any time to pick up dependency changes.
-  venv_state=reused
-  source venv/bin/activate
-else
-  venv_state=created
-  # --clear replaces a partial environment left behind by an interrupted run.
-  if [ -x "$(command -v uv)" ]; then
-    uv venv --clear --seed venv
-  else
-    python3 -m venv --clear venv
-  fi
-  source venv/bin/activate
-fi
-
-if ! [ -x "$(command -v uv)" ]; then
-  python3 -m pip install uv
-fi
-
-uv pip install setuptools wheel
-uv pip install -e ".[dev,test]" --config-settings editable_mode=compat
-
-# A worktree shares one git hooks directory with the main checkout it was
-# created from, so hooks are installed from the main checkout only. Installing
-# from a worktree would point the shared hook at that worktree's virtual
-# environment, breaking it for everyone once the worktree is removed.
-git_dir="$(git rev-parse --absolute-git-dir 2>/dev/null || true)"
-common_dir="$(git rev-parse --path-format=absolute --git-common-dir 2>/dev/null || true)"
-if [ -n "$common_dir" ] && [ "$git_dir" = "$common_dir" ]; then
-  # --overwrite replaces any hook already in place. Without it, prek finds a
-  # previously installed pre-commit hook, moves it aside to
-  # .git/hooks/pre-commit.legacy and keeps calling it, so every commit would
-  # run both tools.
-  prek install --overwrite
-
-  # Prepares the virtual environment for new checkouts and worktrees. Installed
-  # once here, it covers every worktree created from this checkout.
-  if [ -d "$common_dir/hooks" ]; then
-    cp script/git-hooks/post-checkout "$common_dir/hooks/post-checkout"
-    chmod +x "$common_dir/hooks/post-checkout"
-  fi
-fi
-
-mkdir -p .temp
-
-echo
-echo
-case "$venv_state" in
-  created)
-    echo "Virtual environment created at ./venv. Run 'source venv/bin/activate' to use it."
-    ;;
-  reused)
-    echo "Dependencies updated in the existing ./venv. Run 'source venv/bin/activate' to use it."
-    ;;
-  active)
-    echo "Dependencies installed into the active virtual environment:"
-    echo "  $VIRTUAL_ENV"
-    echo "It is already active in this shell, so no 'source venv/bin/activate' is needed."
-    ;;
-esac
+exec python3 "$(dirname "$0")/setup.py" "$@"

script/setup.bat

@@ -1,28 +1 @@
-@echo off
-
-if defined VIRTUAL_ENV goto :install
-
-echo Starting the Virtual Environment
-python -m venv venv
-call venv/Scripts/activate
-echo Running the Virtual Environment
-
-:install
-
-echo Installing required packages...
-
-python.exe -m pip install --upgrade pip
-
-pip3 install -r requirements.txt -r requirements_test.txt -r requirements_dev.txt
-pip3 install setuptools wheel
-pip3 install -e ".[dev,test]" --config-settings editable_mode=compat
-
-rem --overwrite replaces any hook already in place. Without it, prek finds a
-rem previously installed pre-commit hook, moves it aside to
-rem .git/hooks/pre-commit.legacy and keeps calling it, so every commit would
-rem run both tools.
-prek install --overwrite
-
-echo .
-echo .
-echo Virtual environment created. Run 'venv/Scripts/activate' to use it.
+@python "%~dp0setup.py" %*

script/setup.py

@@ -0,0 +1,222 @@
+#!/usr/bin/env python3
+"""Set up the ESPHome development environment.
+
+Shared implementation behind script/setup and script/setup.bat, so the Unix and
+Windows entry points cannot drift apart. Uses only the standard library: it runs
+before any dependency has been installed.
+"""
+
+import os
+from pathlib import Path
+import shutil
+import subprocess
+import sys
+import sysconfig
+
+MIN_PYTHON = (3, 12)
+
+ROOT = Path(__file__).resolve().parent.parent
+DEFAULT_VENV = ROOT / "venv"
+POST_CHECKOUT_HOOK = ROOT / "script" / "git-hooks" / "post-checkout"
+
+# State of the environment the dependencies end up in, used for the closing
+# message.
+VENV_ACTIVE = "active"
+VENV_REUSED = "reused"
+VENV_CREATED = "created"
+
+
+def bin_dir(venv: Path) -> Path:
+    """Return the directory holding a virtual environment's executables.
+
+    The "venv" scheme resolves to bin on Unix and Scripts on Windows, so the
+    layout does not have to be hardcoded here.
+    """
+    base = str(venv)
+    return Path(
+        sysconfig.get_path("scripts", "venv", vars={"base": base, "platbase": base})
+    )
+
+
+def venv_python(venv: Path) -> Path:
+    """Return the path to a virtual environment's interpreter."""
+    name = "python.exe" if os.name == "nt" else "python"
+    return bin_dir(venv) / name
+
+
+def run(command: list[str], env: dict[str, str] | None = None) -> None:
+    """Run a command, aborting the whole script if it fails."""
+    print(f"+ {' '.join(command)}", flush=True)
+    result = subprocess.run(command, cwd=ROOT, env=env, check=False)
+    if result.returncode != 0:
+        # Some tools fail without printing anything, so name the step that broke.
+        print(
+            f"Failed with exit code {result.returncode}: {command[0]}", file=sys.stderr
+        )
+        raise SystemExit(result.returncode)
+
+
+def git_output(*args: str) -> str:
+    """Return the trimmed output of a git command, or "" if it cannot be run."""
+    try:
+        result = subprocess.run(
+            ["git", *args], cwd=ROOT, capture_output=True, text=True, check=False
+        )
+    except OSError:
+        # Git is not required to install the dependencies, only to install hooks.
+        return ""
+    if result.returncode != 0:
+        return ""
+    return result.stdout.strip()
+
+
+def create_venv(venv: Path) -> None:
+    """Create a virtual environment, replacing anything already at the path."""
+    # --clear replaces a partial environment left behind by an interrupted run.
+    if (uv := shutil.which("uv")) is not None:
+        run([uv, "venv", "--clear", "--seed", str(venv)])
+    else:
+        run([sys.executable, "-m", "venv", "--clear", str(venv)])
+
+
+def venv_environment(venv: Path) -> dict[str, str]:
+    """Return the environment child processes need to target a virtual env.
+
+    Equivalent to sourcing the environment's activate script: tools such as uv
+    and prek pick the environment up from VIRTUAL_ENV and PATH.
+    """
+    env = dict(os.environ)
+    env["VIRTUAL_ENV"] = str(venv)
+    env.pop("PYTHONHOME", None)
+    path = str(bin_dir(venv))
+    # An empty entry would be appended if PATH is unset, and on Unix that means
+    # the working directory is searched for executables.
+    if existing := env.get("PATH"):
+        path = os.pathsep.join([path, existing])
+    env["PATH"] = path
+    return env
+
+
+def find_uv(venv: Path, env: dict[str, str]) -> str:
+    """Return the path to uv, installing it into the environment if needed."""
+    if (uv := shutil.which("uv", path=env["PATH"])) is not None:
+        return uv
+    run([str(venv_python(venv)), "-m", "pip", "install", "uv"], env=env)
+    if (uv := shutil.which("uv", path=env["PATH"])) is not None:
+        return uv
+    raise SystemExit("uv could not be installed, aborting.")
+
+
+def install_dependencies(venv: Path, env: dict[str, str]) -> None:
+    """Install ESPHome and its development dependencies into the environment."""
+    uv = find_uv(venv, env)
+    run([uv, "pip", "install", "setuptools", "wheel"], env=env)
+    # The dev and test extras pull in requirements_dev.txt and
+    # requirements_test.txt, and the package itself pulls in requirements.txt,
+    # so this single install covers every requirements file.
+    run(
+        [
+            uv,
+            "pip",
+            "install",
+            "-e",
+            ".[dev,test]",
+            "--config-settings",
+            "editable_mode=compat",
+        ],
+        env=env,
+    )
+
+
+def install_git_hooks(env: dict[str, str]) -> None:
+    """Install the git hooks, but only when run from the main checkout.
+
+    A worktree shares one git hooks directory with the main checkout it was
+    created from. Installing from a worktree would point the shared hook at that
+    worktree's virtual environment, breaking it for everyone once the worktree is
+    removed.
+    """
+    git_dir = git_output("rev-parse", "--absolute-git-dir")
+    common_dir = git_output("rev-parse", "--path-format=absolute", "--git-common-dir")
+    if not git_dir or not common_dir or Path(git_dir) != Path(common_dir):
+        return
+
+    prek = shutil.which("prek", path=env["PATH"])
+    if prek is None:
+        raise SystemExit("prek was not installed, aborting.")
+    # --overwrite replaces any hook already in place. Without it, prek finds a
+    # previously installed pre-commit hook, moves it aside to
+    # .git/hooks/pre-commit.legacy and keeps calling it, so every commit would
+    # run both tools.
+    run([prek, "install", "--overwrite"], env=env)
+
+    # Prepares the virtual environment for new checkouts and worktrees. Installed
+    # once here, it covers every worktree created from this checkout.
+    hooks_dir = Path(common_dir) / "hooks"
+    if hooks_dir.is_dir():
+        installed = hooks_dir / "post-checkout"
+        shutil.copyfile(POST_CHECKOUT_HOOK, installed)
+        installed.chmod(0o755)
+
+
+def activate_hint() -> str:
+    """Return the command that activates the environment this script creates."""
+    activate = bin_dir(DEFAULT_VENV).relative_to(ROOT) / "activate"
+    if os.name == "nt":
+        return str(activate)
+    return f"source {activate.as_posix()}"
+
+
+def report(state: str, venv: Path) -> None:
+    """Print the closing message for the environment that was set up."""
+    location = f"./{DEFAULT_VENV.name}"
+    print()
+    print()
+    if state == VENV_ACTIVE:
+        print("Dependencies installed into the active virtual environment:")
+        print(f"  {venv}")
+        print(
+            f"It is already active in this shell, so no '{activate_hint()}' is needed."
+        )
+    elif state == VENV_REUSED:
+        print(
+            f"Dependencies updated in the existing {location}. "
+            f"Run '{activate_hint()}' to use it."
+        )
+    else:
+        print(
+            f"Virtual environment created at {location}. "
+            f"Run '{activate_hint()}' to use it."
+        )
+
+
+def main() -> None:
+    """Set up the development environment."""
+    if sys.version_info < MIN_PYTHON:
+        raise SystemExit(
+            f"ESPHome needs Python {MIN_PYTHON[0]}.{MIN_PYTHON[1]} or newer, "
+            f"but this is Python {sys.version.split()[0]}."
+        )
+
+    # A virtual environment that is already active (for example the
+    # devcontainer's pre-provisioned esphome-venv) is installed into rather than
+    # creating a ./venv in the workspace.
+    if active := os.environ.get("VIRTUAL_ENV"):
+        state, venv = VENV_ACTIVE, Path(active)
+    elif venv_python(DEFAULT_VENV).is_file():
+        # Reuse the environment from an earlier run, so this script can be run
+        # again at any time to pick up dependency changes.
+        state, venv = VENV_REUSED, DEFAULT_VENV
+    else:
+        state, venv = VENV_CREATED, DEFAULT_VENV
+        create_venv(venv)
+
+    env = venv_environment(venv)
+    install_dependencies(venv, env)
+    install_git_hooks(env)
+    (ROOT / ".temp").mkdir(exist_ok=True)
+    report(state, venv)
+
+
+if __name__ == "__main__":
+    main()

tests/script/test_setup.py

@@ -0,0 +1,562 @@
+"""Tests for script/setup.py."""
+
+import importlib.util
+import os
+from pathlib import Path, PurePosixPath, PureWindowsPath
+import runpy
+import sys
+from types import ModuleType
+from unittest.mock import Mock, call, patch
+
+import pytest
+
+_SCRIPT = Path(__file__).parents[2] / "script" / "setup.py"
+
+
+def _load_module() -> ModuleType:
+    spec = importlib.util.spec_from_file_location("script_setup", _SCRIPT)
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    return module
+
+
+@pytest.fixture
+def script_setup() -> ModuleType:
+    """Fresh import of script/setup.py, isolated from other tests."""
+    return _load_module()
+
+
+# --- bin_dir / venv_python / activate_hint -----------------------------------
+
+
+def test_bin_dir_matches_host_layout(script_setup: ModuleType, tmp_path: Path) -> None:
+    """The venv scheme resolves to Scripts on Windows and bin everywhere else."""
+    expected = "Scripts" if os.name == "nt" else "bin"
+    assert script_setup.bin_dir(tmp_path) == tmp_path / expected
+
+
+# Both flavours are exercised on every host. Pure paths are used because a real
+# Path refuses to change flavour: PosixPath cannot be built on Windows, and
+# WindowsPath cannot be built on Unix.
+
+
+def test_venv_python_posix(script_setup: ModuleType, tmp_path: Path) -> None:
+    with (
+        patch.object(
+            script_setup, "bin_dir", return_value=PurePosixPath("/x/venv/bin")
+        ),
+        patch.object(script_setup.os, "name", "posix"),
+    ):
+        result = script_setup.venv_python(tmp_path)
+    assert result == PurePosixPath("/x/venv/bin/python")
+
+
+def test_venv_python_nt(script_setup: ModuleType, tmp_path: Path) -> None:
+    with (
+        patch.object(
+            script_setup, "bin_dir", return_value=PureWindowsPath(r"C:\x\venv\Scripts")
+        ),
+        patch.object(script_setup.os, "name", "nt"),
+    ):
+        result = script_setup.venv_python(tmp_path)
+    assert result == PureWindowsPath(r"C:\x\venv\Scripts\python.exe")
+
+
+def test_activate_hint_posix(script_setup: ModuleType) -> None:
+    with (
+        patch.object(script_setup, "ROOT", PurePosixPath("/x")),
+        patch.object(
+            script_setup, "bin_dir", return_value=PurePosixPath("/x/venv/bin")
+        ),
+        patch.object(script_setup.os, "name", "posix"),
+    ):
+        hint = script_setup.activate_hint()
+    assert hint == "source venv/bin/activate"
+
+
+def test_activate_hint_nt(script_setup: ModuleType) -> None:
+    with (
+        patch.object(script_setup, "ROOT", PureWindowsPath(r"C:\x")),
+        patch.object(
+            script_setup, "bin_dir", return_value=PureWindowsPath(r"C:\x\venv\Scripts")
+        ),
+        patch.object(script_setup.os, "name", "nt"),
+    ):
+        hint = script_setup.activate_hint()
+    # The nt branch returns str(activate) as-is, skipping the "source " prefix.
+    assert hint == r"venv\Scripts\activate"
+
+
+# --- run -----------------------------------------------------------------
+
+
+def test_run_success(script_setup: ModuleType) -> None:
+    with patch.object(
+        script_setup.subprocess, "run", return_value=Mock(returncode=0)
+    ) as mock_run:
+        script_setup.run(["echo", "hi"])
+    mock_run.assert_called_once_with(
+        ["echo", "hi"], cwd=script_setup.ROOT, env=None, check=False
+    )
+
+
+def test_run_failure_raises_system_exit_with_code(
+    script_setup: ModuleType, capsys: pytest.CaptureFixture[str]
+) -> None:
+    with (
+        patch.object(script_setup.subprocess, "run", return_value=Mock(returncode=7)),
+        pytest.raises(SystemExit) as excinfo,
+    ):
+        script_setup.run(["false"])
+    assert excinfo.value.code == 7
+    assert "Failed with exit code 7: false" in capsys.readouterr().err
+
+
+# --- git_output ------------------------------------------------------------
+
+
+def test_git_output_success_strips_stdout(script_setup: ModuleType) -> None:
+    with patch.object(
+        script_setup.subprocess,
+        "run",
+        return_value=Mock(returncode=0, stdout="  /repo/.git \n"),
+    ) as mock_run:
+        result = script_setup.git_output("rev-parse", "--absolute-git-dir")
+    assert result == "/repo/.git"
+    mock_run.assert_called_once_with(
+        ["git", "rev-parse", "--absolute-git-dir"],
+        cwd=script_setup.ROOT,
+        capture_output=True,
+        text=True,
+        check=False,
+    )
+
+
+def test_git_output_nonzero_returncode_is_empty(script_setup: ModuleType) -> None:
+    with patch.object(
+        script_setup.subprocess,
+        "run",
+        return_value=Mock(returncode=1, stdout="whatever"),
+    ):
+        assert script_setup.git_output("status") == ""
+
+
+def test_git_output_oserror_is_empty(script_setup: ModuleType) -> None:
+    with patch.object(script_setup.subprocess, "run", side_effect=OSError("no git")):
+        assert script_setup.git_output("status") == ""
+
+
+# --- create_venv -----------------------------------------------------------
+
+
+def test_create_venv_uses_uv_when_present(
+    script_setup: ModuleType, tmp_path: Path
+) -> None:
+    venv = tmp_path / "venv"
+    with (
+        patch.object(script_setup.shutil, "which", return_value="/usr/bin/uv"),
+        patch.object(
+            script_setup.subprocess, "run", return_value=Mock(returncode=0)
+        ) as mock_run,
+    ):
+        script_setup.create_venv(venv)
+    mock_run.assert_called_once_with(
+        ["/usr/bin/uv", "venv", "--clear", "--seed", str(venv)],
+        cwd=script_setup.ROOT,
+        env=None,
+        check=False,
+    )
+
+
+def test_create_venv_falls_back_to_venv_module(
+    script_setup: ModuleType, tmp_path: Path
+) -> None:
+    venv = tmp_path / "venv"
+    with (
+        patch.object(script_setup.shutil, "which", return_value=None),
+        patch.object(
+            script_setup.subprocess, "run", return_value=Mock(returncode=0)
+        ) as mock_run,
+    ):
+        script_setup.create_venv(venv)
+    mock_run.assert_called_once_with(
+        [sys.executable, "-m", "venv", "--clear", str(venv)],
+        cwd=script_setup.ROOT,
+        env=None,
+        check=False,
+    )
+
+
+# --- venv_environment --------------------------------------------------------
+
+
+def test_venv_environment_sets_virtual_env_and_prepends_path(
+    script_setup: ModuleType, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    venv = tmp_path / "venv"
+    monkeypatch.setenv("PYTHONHOME", "/somewhere")
+    monkeypatch.setenv("PATH", "/usr/bin:/bin")
+    env = script_setup.venv_environment(venv)
+    assert env["VIRTUAL_ENV"] == str(venv)
+    assert "PYTHONHOME" not in env
+    expected_prefix = str(script_setup.bin_dir(venv)) + os.pathsep
+    assert env["PATH"] == expected_prefix + "/usr/bin:/bin"
+
+
+def test_venv_environment_path_fallback_when_unset(
+    script_setup: ModuleType, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    venv = tmp_path / "venv"
+    monkeypatch.delenv("PATH", raising=False)
+    env = script_setup.venv_environment(venv)
+    # No trailing separator: an empty PATH entry means "search the cwd".
+    assert env["PATH"] == str(script_setup.bin_dir(venv))
+
+
+# --- find_uv -----------------------------------------------------------------
+
+
+def test_find_uv_found_immediately(script_setup: ModuleType, tmp_path: Path) -> None:
+    venv = tmp_path / "venv"
+    env = {"PATH": "/usr/bin"}
+    with (
+        patch.object(script_setup.shutil, "which", return_value="/usr/bin/uv"),
+        patch.object(script_setup.subprocess, "run") as mock_run,
+    ):
+        result = script_setup.find_uv(venv, env)
+    assert result == "/usr/bin/uv"
+    mock_run.assert_not_called()
+
+
+def test_find_uv_installed_then_found(script_setup: ModuleType, tmp_path: Path) -> None:
+    venv = tmp_path / "venv"
+    env = {"PATH": "/usr/bin"}
+    with (
+        patch.object(script_setup.shutil, "which", side_effect=[None, "/usr/bin/uv"]),
+        patch.object(
+            script_setup.subprocess, "run", return_value=Mock(returncode=0)
+        ) as mock_run,
+    ):
+        result = script_setup.find_uv(venv, env)
+    assert result == "/usr/bin/uv"
+    mock_run.assert_called_once_with(
+        [str(script_setup.venv_python(venv)), "-m", "pip", "install", "uv"],
+        cwd=script_setup.ROOT,
+        env=env,
+        check=False,
+    )
+
+
+def test_find_uv_still_missing_raises_system_exit(
+    script_setup: ModuleType, tmp_path: Path
+) -> None:
+    venv = tmp_path / "venv"
+    env = {"PATH": "/usr/bin"}
+    with (
+        patch.object(script_setup.shutil, "which", side_effect=[None, None]),
+        patch.object(script_setup.subprocess, "run", return_value=Mock(returncode=0)),
+        pytest.raises(SystemExit, match="uv could not be installed"),
+    ):
+        script_setup.find_uv(venv, env)
+
+
+# --- install_dependencies -----------------------------------------------------
+
+
+def test_install_dependencies_installs_setuptools_then_project(
+    script_setup: ModuleType, tmp_path: Path
+) -> None:
+    venv = tmp_path / "venv"
+    env = {"PATH": "/usr/bin"}
+    with (
+        patch.object(script_setup.shutil, "which", return_value="/usr/bin/uv"),
+        patch.object(
+            script_setup.subprocess, "run", return_value=Mock(returncode=0)
+        ) as mock_run,
+    ):
+        script_setup.install_dependencies(venv, env)
+    assert mock_run.call_args_list == [
+        call(
+            ["/usr/bin/uv", "pip", "install", "setuptools", "wheel"],
+            cwd=script_setup.ROOT,
+            env=env,
+            check=False,
+        ),
+        call(
+            [
+                "/usr/bin/uv",
+                "pip",
+                "install",
+                "-e",
+                ".[dev,test]",
+                "--config-settings",
+                "editable_mode=compat",
+            ],
+            cwd=script_setup.ROOT,
+            env=env,
+            check=False,
+        ),
+    ]
+
+
+# --- install_git_hooks ---------------------------------------------------------
+
+
+def _fake_git_output(git_dir: str, common_dir: str):
+    def _run(*args: str) -> str:
+        if "--absolute-git-dir" in args:
+            return git_dir
+        return common_dir
+
+    return _run
+
+
+def test_install_git_hooks_returns_early_when_git_dir_empty(
+    script_setup: ModuleType,
+) -> None:
+    env = {"PATH": "/usr/bin"}
+    with (
+        patch.object(
+            script_setup, "git_output", side_effect=_fake_git_output("", "/repo/.git")
+        ),
+        patch.object(script_setup.subprocess, "run") as mock_run,
+    ):
+        script_setup.install_git_hooks(env)
+    mock_run.assert_not_called()
+
+
+def test_install_git_hooks_returns_early_when_common_dir_empty(
+    script_setup: ModuleType,
+) -> None:
+    env = {"PATH": "/usr/bin"}
+    with (
+        patch.object(
+            script_setup, "git_output", side_effect=_fake_git_output("/repo/.git", "")
+        ),
+        patch.object(script_setup.subprocess, "run") as mock_run,
+    ):
+        script_setup.install_git_hooks(env)
+    mock_run.assert_not_called()
+
+
+def test_install_git_hooks_returns_early_for_worktree(
+    script_setup: ModuleType,
+) -> None:
+    """A worktree's git-dir differs from the shared common-dir."""
+    env = {"PATH": "/usr/bin"}
+    with (
+        patch.object(
+            script_setup,
+            "git_output",
+            side_effect=_fake_git_output("/repo/.git/worktrees/wt", "/repo/.git"),
+        ),
+        patch.object(script_setup.subprocess, "run") as mock_run,
+    ):
+        script_setup.install_git_hooks(env)
+    mock_run.assert_not_called()
+
+
+def test_install_git_hooks_missing_prek_raises_system_exit(
+    script_setup: ModuleType,
+) -> None:
+    env = {"PATH": "/usr/bin"}
+    with (
+        patch.object(
+            script_setup,
+            "git_output",
+            side_effect=_fake_git_output("/repo/.git", "/repo/.git"),
+        ),
+        patch.object(script_setup.shutil, "which", return_value=None),
+        patch.object(script_setup.subprocess, "run") as mock_run,
+        pytest.raises(SystemExit, match="prek was not installed"),
+    ):
+        script_setup.install_git_hooks(env)
+    mock_run.assert_not_called()
+
+
+def test_install_git_hooks_happy_path_installs_hook(
+    script_setup: ModuleType, tmp_path: Path
+) -> None:
+    env = {"PATH": "/usr/bin"}
+    common_dir = tmp_path / "repo" / ".git"
+    hooks_dir = common_dir / "hooks"
+    hooks_dir.mkdir(parents=True)
+    source_hook = tmp_path / "post-checkout"
+    source_hook.write_text("#!/bin/sh\necho post-checkout\n")
+
+    with (
+        patch.object(script_setup, "POST_CHECKOUT_HOOK", source_hook),
+        patch.object(
+            script_setup,
+            "git_output",
+            side_effect=_fake_git_output(str(common_dir), str(common_dir)),
+        ),
+        patch.object(script_setup.shutil, "which", return_value="/usr/bin/prek"),
+        patch.object(
+            script_setup.subprocess, "run", return_value=Mock(returncode=0)
+        ) as mock_run,
+    ):
+        script_setup.install_git_hooks(env)
+
+    mock_run.assert_called_once_with(
+        ["/usr/bin/prek", "install", "--overwrite"],
+        cwd=script_setup.ROOT,
+        env=env,
+        check=False,
+    )
+    installed = hooks_dir / "post-checkout"
+    assert installed.read_text() == source_hook.read_text()
+    if os.name != "nt":
+        # Windows has no POSIX permission bits for chmod to set.
+        assert (installed.stat().st_mode & 0o777) == 0o755
+
+
+def test_install_git_hooks_skips_copy_when_hooks_dir_missing(
+    script_setup: ModuleType, tmp_path: Path
+) -> None:
+    """The prek install still runs when the hooks directory does not exist."""
+    env = {"PATH": "/usr/bin"}
+    common_dir = tmp_path / "repo" / ".git"
+    common_dir.mkdir(parents=True)  # no "hooks" subdirectory created
+
+    with (
+        patch.object(
+            script_setup,
+            "git_output",
+            side_effect=_fake_git_output(str(common_dir), str(common_dir)),
+        ),
+        patch.object(script_setup.shutil, "which", return_value="/usr/bin/prek"),
+        patch.object(
+            script_setup.subprocess, "run", return_value=Mock(returncode=0)
+        ) as mock_run,
+    ):
+        script_setup.install_git_hooks(env)
+
+    mock_run.assert_called_once()
+    assert not (common_dir / "hooks").exists()
+
+
+# --- report ------------------------------------------------------------------
+
+
+def test_report_active_state(
+    script_setup: ModuleType, capsys: pytest.CaptureFixture
+) -> None:
+    venv = Path("/opt/esphome-venv")
+    script_setup.report(script_setup.VENV_ACTIVE, venv)
+    out = capsys.readouterr().out
+    assert "Dependencies installed into the active virtual environment:" in out
+    assert str(venv) in out
+    assert "is already active in this shell" in out
+
+
+def test_report_reused_state(
+    script_setup: ModuleType, capsys: pytest.CaptureFixture
+) -> None:
+    script_setup.report(script_setup.VENV_REUSED, script_setup.DEFAULT_VENV)
+    out = capsys.readouterr().out
+    assert "Dependencies updated in the existing ./venv" in out
+
+
+def test_report_created_state(
+    script_setup: ModuleType, capsys: pytest.CaptureFixture
+) -> None:
+    script_setup.report(script_setup.VENV_CREATED, script_setup.DEFAULT_VENV)
+    out = capsys.readouterr().out
+    assert "Virtual environment created at ./venv" in out
+
+
+# --- main --------------------------------------------------------------------
+
+
+def test_main_raises_system_exit_when_python_too_old(
+    script_setup: ModuleType,
+) -> None:
+    with (
+        patch.object(script_setup.sys, "version_info", (3, 11, 5)),
+        pytest.raises(SystemExit, match="ESPHome needs Python 3.12"),
+    ):
+        script_setup.main()
+
+
+def test_main_uses_active_virtual_env(
+    script_setup: ModuleType, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    active_venv = tmp_path / "active-venv"
+    monkeypatch.setenv("VIRTUAL_ENV", str(active_venv))
+    with (
+        patch.object(script_setup, "ROOT", tmp_path),
+        patch.object(script_setup, "create_venv") as mock_create_venv,
+        patch.object(script_setup, "install_dependencies") as mock_install_deps,
+        patch.object(script_setup, "install_git_hooks") as mock_install_hooks,
+        patch.object(script_setup, "report") as mock_report,
+    ):
+        script_setup.main()
+    mock_create_venv.assert_not_called()
+    mock_install_deps.assert_called_once()
+    mock_install_hooks.assert_called_once()
+    mock_report.assert_called_once_with(script_setup.VENV_ACTIVE, active_venv)
+    assert (tmp_path / ".temp").is_dir()
+
+
+def test_main_reuses_existing_venv(
+    script_setup: ModuleType, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    monkeypatch.delenv("VIRTUAL_ENV", raising=False)
+    default_venv = tmp_path / "venv"
+    python_path = script_setup.venv_python(default_venv)
+    python_path.parent.mkdir(parents=True)
+    python_path.touch()
+
+    with (
+        patch.object(script_setup, "ROOT", tmp_path),
+        patch.object(script_setup, "DEFAULT_VENV", default_venv),
+        patch.object(script_setup, "create_venv") as mock_create_venv,
+        patch.object(script_setup, "install_dependencies") as mock_install_deps,
+        patch.object(script_setup, "install_git_hooks") as mock_install_hooks,
+        patch.object(script_setup, "report") as mock_report,
+    ):
+        script_setup.main()
+    mock_create_venv.assert_not_called()
+    mock_install_deps.assert_called_once()
+    mock_install_hooks.assert_called_once()
+    mock_report.assert_called_once_with(script_setup.VENV_REUSED, default_venv)
+    assert (tmp_path / ".temp").is_dir()
+
+
+def test_main_creates_new_venv(
+    script_setup: ModuleType, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    monkeypatch.delenv("VIRTUAL_ENV", raising=False)
+    default_venv = tmp_path / "venv"  # does not exist yet
+
+    with (
+        patch.object(script_setup, "ROOT", tmp_path),
+        patch.object(script_setup, "DEFAULT_VENV", default_venv),
+        patch.object(script_setup, "create_venv") as mock_create_venv,
+        patch.object(script_setup, "install_dependencies") as mock_install_deps,
+        patch.object(script_setup, "install_git_hooks") as mock_install_hooks,
+        patch.object(script_setup, "report") as mock_report,
+    ):
+        script_setup.main()
+    mock_create_venv.assert_called_once_with(default_venv)
+    mock_install_deps.assert_called_once()
+    mock_install_hooks.assert_called_once()
+    mock_report.assert_called_once_with(script_setup.VENV_CREATED, default_venv)
+    assert (tmp_path / ".temp").is_dir()
+
+
+def test_run_as_script_calls_main(tmp_path: Path) -> None:
+    """The __main__ guard runs the whole flow, with every side effect stubbed."""
+    completed = Mock(returncode=0, stdout="")
+    with (
+        patch("subprocess.run", return_value=completed) as mock_run,
+        patch("shutil.which", return_value="/usr/bin/uv"),
+        patch("pathlib.Path.mkdir") as mock_mkdir,
+        patch.dict(os.environ, {"VIRTUAL_ENV": str(tmp_path / "env")}),
+    ):
+        runpy.run_path(str(_SCRIPT), run_name="__main__")
+
+    # The dependency install ran, and git reported no hooks directory to touch.
+    assert mock_run.called
+    mock_mkdir.assert_called_once_with(exist_ok=True)