refactor!: port shell scripts to Python package

Bash scripts were untestable and duplicated device/LUKS/mount logic;
the lim/ package centralizes it behind one subprocess wrapper and a
YAML image catalog (single point of truth).

BREAKING CHANGE: scripts/*.sh removed. Use `lim --type <cmd>`; new
types mount/umount/single-boot/raid1-boot/lock/unlock/import/export
replace direct script calls. --extra is deprecated and ignored.

- distributions.yml + lim/catalog.py hold the image catalog (PyYAML)
- pytest suite: 102 tests with mocked subprocess (tests/unit) and a
  250-line max file-length guard (tests/lint)
- ruff strict (select ALL), GitHub Actions CI, Dependabot; Travis gone
- Makefile: install (symlink ~/.local/bin/lim) and test targets
- fixes over bash: SUDO_USER-aware chown, mmcblk/nvme partition paths,
  sha512 checksum support, whole-pipeline failure detection, blkid
  UUID fallback for pre-mounted images, conditional fstab seeding for
  PARTUUID/LABEL images, clean errors for missing binaries

tests/unit/test_catalog.py

@@ -0,0 +1,24 @@
+from lim import catalog
+
+
+def test_catalog_contains_all_sections():
+    assert catalog.arch_rpi_images()
+    assert catalog.manjaro_gnome_releases()
+    assert catalog.retropie_images()
+    assert catalog.mkinitcpio_modules_by_rpi()
+
+
+def test_arch_entries_are_complete():
+    for version, entry in catalog.arch_rpi_images().items():
+        assert entry["image"], version
+        assert entry["luks_memory_cost"].isdigit(), version
+
+
+def test_mkinitcpio_covers_every_arch_rpi_version():
+    assert set(catalog.mkinitcpio_modules_by_rpi()) == set(catalog.arch_rpi_images())
+
+
+def test_manjaro_entries_have_url_and_image():
+    for release, entry in catalog.manjaro_gnome_releases().items():
+        assert entry["url"].startswith("https://"), release
+        assert entry["image"], release

tests/unit/test_cli.py

@@ -0,0 +1,65 @@
+import pytest
+
+from lim import cli, system
+from lim.cli import Command
+from lim.errors import LimError
+
+
+@pytest.fixture(autouse=True)
+def no_input(monkeypatch):
+    monkeypatch.setattr(
+        "builtins.input", lambda *args: (_ for _ in ()).throw(AssertionError("unexpected prompt"))
+    )
+
+
+def test_every_command_dispatches_to_its_function(monkeypatch):
+    executed = []
+    monkeypatch.setitem(
+        cli.COMMANDS, "lock", Command(lambda: executed.append("lock"), "d", needs_root=False)
+    )
+    cli.main(["--type", "lock", "--auto-confirm"])
+    assert executed == ["lock"]
+
+
+def test_needs_root_command_requests_root(monkeypatch):
+    escalated = []
+    monkeypatch.setattr(system, "ensure_root", lambda: escalated.append(True))
+    monkeypatch.setitem(
+        cli.COMMANDS, "backup", Command(lambda: None, "d", needs_root=True)
+    )
+    cli.main(["--type", "backup", "--auto-confirm"])
+    assert escalated == [True]
+
+
+def test_confirmation_prompt_waits_for_enter(monkeypatch):
+    prompts = []
+    executed = []
+    monkeypatch.setattr("builtins.input", lambda *args: prompts.append(args) or "")
+    monkeypatch.setitem(
+        cli.COMMANDS, "lock", Command(lambda: executed.append(True), "d", needs_root=False)
+    )
+    cli.main(["--type", "lock"])
+    assert len(prompts) == 1
+    assert executed == [True]
+
+
+def test_lim_error_exits_with_code_1(monkeypatch):
+    def failing():
+        raise LimError("boom")
+
+    monkeypatch.setitem(cli.COMMANDS, "lock", Command(failing, "d", needs_root=False))
+    with pytest.raises(SystemExit) as excinfo:
+        cli.main(["--type", "lock", "--auto-confirm"])
+    assert excinfo.value.code == 1
+
+
+def test_unknown_type_is_rejected_by_argparse():
+    with pytest.raises(SystemExit) as excinfo:
+        cli.main(["--type", "does-not-exist"])
+    assert excinfo.value.code == 2
+
+
+def test_all_registered_commands_have_descriptions():
+    for name, command in cli.COMMANDS.items():
+        assert command.description, name
+        assert callable(command.func), name

tests/unit/test_device.py

@@ -0,0 +1,84 @@
+import pytest
+
+from lim import device
+from lim.device import Device
+from lim.errors import LimError
+
+
+class TestPartitionNaming:
+    def test_letter_suffix_devices_append_number(self):
+        assert Device("sda").partition(1) == "/dev/sda1"
+        assert Device("sdb").partition(2) == "/dev/sdb2"
+
+    def test_digit_suffix_devices_get_p_infix(self):
+        assert Device("mmcblk0").partition(1) == "/dev/mmcblk0p1"
+        assert Device("nvme0n1").partition(2) == "/dev/nvme0n1p2"
+
+
+class TestOptimalBlocksize:
+    def test_uses_64_times_physical_block_size(self, tmp_path):
+        queue = tmp_path / "sda" / "queue"
+        queue.mkdir(parents=True)
+        (queue / "physical_block_size").write_text("512\n")
+        assert device.optimal_blocksize("sda", tmp_path) == str(64 * 512)
+
+    def test_falls_back_to_4k_when_missing(self, tmp_path):
+        assert device.optimal_blocksize("sda", tmp_path) == "4K"
+
+    def test_falls_back_to_4k_on_garbage(self, tmp_path):
+        queue = tmp_path / "sda" / "queue"
+        queue.mkdir(parents=True)
+        (queue / "physical_block_size").write_text("not-a-number")
+        assert device.optimal_blocksize("sda", tmp_path) == "4K"
+
+
+class TestOverwriteDevice:
+    @pytest.fixture
+    def sda(self, monkeypatch):
+        monkeypatch.setattr(Device, "optimal_blocksize", property(lambda self: "4K"))
+        return Device("sda")
+
+    def test_full_overwrite(self, sda, fake_runner, answers):
+        answers("y")
+        device.overwrite_device(sda)
+        dd_calls = fake_runner.find("dd", "if=/dev/zero", "of=/dev/sda")
+        assert len(dd_calls) == 1
+        assert not any("count=" in part for part in dd_calls[0])
+
+    @pytest.mark.parametrize("answer", ["", "N"])
+    def test_skip(self, sda, fake_runner, answers, answer):
+        answers(answer)
+        device.overwrite_device(sda)
+        assert fake_runner.find("dd") == []
+
+    def test_block_count(self, sda, fake_runner, answers):
+        answers("34")
+        device.overwrite_device(sda)
+        assert len(fake_runner.find("dd", "count=34", "bs=4K")) == 1
+
+    def test_invalid_input_raises(self, sda, fake_runner, answers):
+        answers("nonsense")
+        with pytest.raises(LimError):
+            device.overwrite_device(sda)
+
+
+class TestSelectDevice:
+    def test_valid_device(self, fake_runner, answers, monkeypatch):
+        answers("sda")
+        monkeypatch.setattr(device, "is_block_device", lambda path: path == "/dev/sda")
+        assert device.select_device() == Device("sda")
+
+    def test_invalid_device_raises(self, fake_runner, answers, monkeypatch):
+        answers("nope")
+        monkeypatch.setattr(device, "is_block_device", lambda path: False)
+        with pytest.raises(LimError):
+            device.select_device()
+
+
+def test_is_mounted(fake_runner):
+    fake_runner.outputs["mount"] = (
+        "/dev/sda1 on /boot type vfat (rw)\n/dev/mapper/x on /media/x type btrfs (rw)"
+    )
+    assert device.is_mounted("/dev/sda1")
+    assert device.is_mounted("/media/x")
+    assert not device.is_mounted("/dev/sdb")

tests/unit/test_fsutil.py

@@ -0,0 +1,35 @@
+import pytest
+
+from lim import fsutil
+from lim.errors import LimError
+
+
+def test_replace_in_file_replaces_all_occurrences(tmp_path):
+    target = tmp_path / "conf"
+    target.write_text("MODULES=()\nHOOKS=(base)\nMODULES=()\n")
+    fsutil.replace_in_file("MODULES=()", "MODULES=(x)", target)
+    assert target.read_text() == "MODULES=(x)\nHOOKS=(base)\nMODULES=(x)\n"
+
+
+def test_replace_in_file_fails_when_search_missing(tmp_path):
+    target = tmp_path / "conf"
+    target.write_text("nothing here\n")
+    with pytest.raises(LimError):
+        fsutil.replace_in_file("MODULES=()", "MODULES=(x)", target)
+    assert target.read_text() == "nothing here\n"
+
+
+def test_ensure_line_appends_once(tmp_path):
+    target = tmp_path / "fstab"
+    target.write_text("existing entry\n")
+    assert fsutil.ensure_line_in_file("new entry", target) is True
+    assert fsutil.ensure_line_in_file("new entry", target) is False
+    assert target.read_text() == "existing entry\nnew entry\n"
+
+
+def test_ensure_line_creates_file_and_handles_missing_newline(tmp_path):
+    target = tmp_path / "crypttab"
+    assert fsutil.ensure_line_in_file("first", target) is True
+    target.write_text("no newline at end")
+    assert fsutil.ensure_line_in_file("second", target) is True
+    assert target.read_text() == "no newline at end\nsecond\n"

tests/unit/test_image_session.py

@@ -0,0 +1,62 @@
+from lim.device import Device
+from lim.image.session import ImageSession
+
+
+def test_partition_paths_for_sd_card():
+    session = ImageSession(Device("mmcblk0"))
+    assert session.boot_partition_path == "/dev/mmcblk0p1"
+    assert session.root_partition_path == "/dev/mmcblk0p2"
+    assert session.root_mapper_path == "/dev/mmcblk0p2"
+
+
+def test_decrypt_root_on_luks_partition(fake_runner):
+    fake_runner.outputs["-s TYPE"] = "crypto_LUKS"
+    fake_runner.outputs["-s UUID"] = "uuid-1"
+    session = ImageSession(Device("sda"))
+    session.decrypt_root()
+    assert session.root_mapper_name == "linux-image-manager-uuid-1"
+    assert session.root_mapper_path == "/dev/mapper/linux-image-manager-uuid-1"
+    assert len(fake_runner.find("cryptsetup", "luksOpen", "/dev/sda2")) == 1
+
+
+def test_decrypt_root_skips_plain_partition(fake_runner):
+    fake_runner.outputs["-s TYPE"] = "ext4"
+    session = ImageSession(Device("sda"))
+    session.decrypt_root()
+    assert session.root_mapper_name is None
+    assert session.root_mapper_path == "/dev/sda2"
+    assert fake_runner.find("cryptsetup") == []
+
+
+def test_destructor_unmounts_everything_despite_failures(tmp_path, fake_runner):
+    session = ImageSession(Device("sda"))
+    session.working_folder = tmp_path
+    session.boot_mount_path = tmp_path / "boot"
+    session.root_mount_path = tmp_path / "root"
+    fake_runner.failures.add("umount")  # every umount fails; cleanup must go on
+
+    session.destructor()
+
+    umounted = [cmd[-1] for cmd in fake_runner.find("umount")]
+    root = str(session.root_mount_path)
+    # chroot binds first (deepest path first), then the partitions
+    assert umounted == [
+        f"{root}/dev/pts",
+        f"{root}/dev",
+        f"{root}/proc",
+        f"{root}/sys",
+        f"{root}/boot",
+        root,
+        str(session.boot_mount_path),
+    ]
+    removed = [cmd[-1] for cmd in fake_runner.find("rmdir")]
+    assert removed == [root, str(session.boot_mount_path), str(tmp_path)]
+
+
+def test_destructor_closes_luks_mapper(tmp_path, fake_runner):
+    fake_runner.outputs["-s TYPE"] = "crypto_LUKS"
+    fake_runner.outputs["-s UUID"] = "uuid-1"
+    session = ImageSession(Device("sda"))
+    session.decrypt_root()
+    session.destructor()
+    assert len(fake_runner.find("luksClose", "linux-image-manager-uuid-1")) == 1

tests/unit/test_image_setup.py

@@ -0,0 +1,143 @@
+import pytest
+
+from lim.errors import LimError
+from lim.image import choosers, raspberry, transfer
+from lim.image.plan import ImagePlan
+from lim.image.session import install_packages
+
+
+@pytest.fixture
+def plan():
+    return ImagePlan()
+
+
+class TestDistributionChoosers:
+    def test_arch_rpi4_uses_aarch64_and_high_memory_cost(self, plan, answers):
+        answers("4")
+        choosers.choose_arch(plan)
+        assert plan.image_name == "ArchLinuxARM-rpi-aarch64-latest.tar.gz"
+        assert plan.luks_memory_cost == "256000"
+        assert plan.raspberry_pi_version == "4"
+        assert plan.download_url == (
+            "http://os.archlinuxarm.org/os/ArchLinuxARM-rpi-aarch64-latest.tar.gz"
+        )
+
+    def test_arch_rpi1_uses_armv7_and_low_memory_cost(self, plan, answers):
+        answers("1")
+        choosers.choose_arch(plan)
+        assert plan.image_name == "ArchLinuxARM-rpi-armv7-latest.tar.gz"
+        assert plan.luks_memory_cost == "64000"
+
+    def test_arch_unknown_version_raises(self, plan, answers):
+        answers("99")
+        with pytest.raises(LimError):
+            choosers.choose_arch(plan)
+
+    def test_manjaro_gnome_25(self, plan, answers):
+        answers("gnome", "25")
+        choosers.choose_manjaro(plan)
+        assert plan.image_name == "manjaro-gnome-25.0.10-251013-linux612.iso"
+        assert plan.base_download_url == "https://download.manjaro.org/gnome/25.0.10/"
+        assert plan.image_checksum is None
+
+    def test_manjaro_raspberrypi_release_sets_rpi_version(self, plan, answers):
+        answers("gnome", "raspberrypi")
+        choosers.choose_manjaro(plan)
+        assert plan.raspberry_pi_version == "4"
+        assert plan.luks_memory_cost == "256000"
+        assert plan.image_name == "Manjaro-ARM-gnome-rpi4-23.02.img.xz"
+
+    def test_manjaro_unknown_flavour_raises(self, plan, answers):
+        answers("kde")
+        with pytest.raises(LimError):
+            choosers.choose_manjaro(plan)
+
+    def test_retropie_rpi3_shares_rpi2_image(self, plan, answers):
+        answers("3")
+        choosers.choose_retropie(plan)
+        assert plan.image_name == "retropie-buster-4.8-rpi2_3_zero2w.img.gz"
+        assert plan.image_checksum == "224e64d8820fc64046ba3850f481c87e"
+
+    def test_unknown_distribution_raises(self, plan, answers):
+        answers("gentoo")
+        with pytest.raises(LimError):
+            choosers.choose_linux_image(plan)
+
+
+class TestPartitionInput:
+    def test_contains_boot_size_and_writes_table(self):
+        script = transfer.arch_partition_input("+500M")
+        assert script.startswith("o\n")
+        assert "\n+500M\n" in script
+        assert script.endswith("w\n")
+
+
+class TestDecompressCommand:
+    @pytest.mark.parametrize(
+        ("name", "expected"),
+        [
+            ("image.zip", ["unzip", "-p"]),
+            ("image.img.gz", ["gunzip", "-c"]),
+            ("image.iso", ["pv"]),
+            ("image.img.xz", ["unxz", "-c"]),
+        ],
+    )
+    def test_known_formats(self, tmp_path, name, expected):
+        path = tmp_path / name
+        command = transfer.decompress_command(path)
+        assert command[: len(expected)] == expected
+        assert command[-1] == str(path)
+
+    def test_unknown_format_raises(self, tmp_path):
+        with pytest.raises(LimError):
+            transfer.decompress_command(tmp_path / "image.rar")
+
+
+class TestInstallPackages:
+    def test_pacman_for_arch(self, tmp_path, fake_runner):
+        install_packages("arch", tmp_path, "btrfs-progs")
+        chroot_calls = [
+            input_text
+            for kind, cmd, input_text in fake_runner.calls
+            if kind == "run" and cmd[0] == "chroot"
+        ]
+        assert chroot_calls == ["pacman --noconfirm -S --needed btrfs-progs"]
+
+    def test_apt_for_retropie(self, tmp_path, fake_runner):
+        install_packages("retropie", tmp_path, "btrfs-progs")
+        chroot_calls = [
+            input_text
+            for kind, cmd, input_text in fake_runner.calls
+            if kind == "run" and cmd[0] == "chroot"
+        ]
+        assert chroot_calls == ["yes | apt install btrfs-progs"]
+
+    def test_unsupported_distribution_raises(self, tmp_path, fake_runner):
+        with pytest.raises(LimError):
+            install_packages("gentoo", tmp_path, "btrfs-progs")
+
+
+class TestConfigureHelpers:
+    def test_configure_sudoers(self, tmp_path):
+        raspberry.configure_sudoers(tmp_path, "administrator")
+        sudoers = tmp_path / "etc/sudoers.d/administrator"
+        assert sudoers.read_text() == "administrator ALL=(ALL:ALL) ALL\n"
+        assert (sudoers.stat().st_mode & 0o777) == 0o440
+
+    def test_configure_ssh_key(self, tmp_path):
+        public_key = tmp_path / "id_rsa.pub"
+        public_key.write_text("ssh-rsa AAAA test@host\n")
+        ssh_folder = tmp_path / "root/home/user/.ssh"
+        authorized_keys = ssh_folder / "authorized_keys"
+        raspberry.configure_ssh_key(str(public_key), ssh_folder, authorized_keys)
+        assert authorized_keys.read_text() == "ssh-rsa AAAA test@host\n"
+        assert (ssh_folder.stat().st_mode & 0o777) == 0o700
+        assert (authorized_keys.stat().st_mode & 0o777) == 0o600
+
+    def test_configure_ssh_key_missing_source_raises(self, tmp_path):
+        with pytest.raises(LimError):
+            raspberry.configure_ssh_key(
+                str(tmp_path / "missing.pub"),
+                tmp_path / ".ssh",
+                tmp_path / ".ssh/authorized_keys",
+            )

tests/unit/test_luks.py

@@ -0,0 +1,59 @@
+import pytest
+
+from lim import luks
+from lim.errors import LimError
+
+LUKS_DUMP = """\
+LUKS header information
+Version:        2
+UUID:           1234-abcd-5678
+"""
+
+
+def test_luks_uuid_parsed_from_dump(fake_runner):
+    fake_runner.outputs["luksDump"] = LUKS_DUMP
+    assert luks.luks_uuid("/dev/sda1") == "1234-abcd-5678"
+
+
+def test_luks_uuid_missing_raises(fake_runner):
+    fake_runner.outputs["luksDump"] = "no uuid here"
+    with pytest.raises(LimError):
+        luks.luks_uuid("/dev/sda1")
+
+
+def test_update_fstab_is_idempotent(tmp_path):
+    fstab = tmp_path / "fstab"
+    fstab.write_text("# existing\n")
+    luks.update_fstab("/dev/mapper/x", "/media/x", fstab_path=fstab)
+    luks.update_fstab("/dev/mapper/x", "/media/x", fstab_path=fstab)
+    lines = fstab.read_text().splitlines()
+    assert lines.count("/dev/mapper/x /media/x btrfs   defaults   0       2") == 1
+
+
+def test_create_luks_key_and_update_crypttab(tmp_path, fake_runner):
+    fake_runner.outputs["luksDump"] = LUKS_DUMP
+    key_dir = tmp_path / "luks-keys"
+    crypttab = tmp_path / "crypttab"
+
+    luks.create_luks_key_and_update_crypttab(
+        "encrypteddrive-sda",
+        "/dev/sda1",
+        key_directory=key_dir,
+        crypttab_path=crypttab,
+    )
+
+    keyfile = key_dir / "encrypteddrive-sda.keyfile"
+    assert len(fake_runner.find("dd", "if=/dev/urandom", f"of={keyfile}")) == 1
+    assert len(fake_runner.find("cryptsetup", "luksAddKey", "/dev/sda1")) == 1
+    assert len(fake_runner.find("cryptsetup", "luksOpen", f"--key-file={keyfile}")) == 1
+    expected_entry = f"encrypteddrive-sda UUID=1234-abcd-5678 {keyfile} luks"
+    assert expected_entry in crypttab.read_text().splitlines()
+
+    # A second run must not duplicate the crypttab entry.
+    luks.create_luks_key_and_update_crypttab(
+        "encrypteddrive-sda",
+        "/dev/sda1",
+        key_directory=key_dir,
+        crypttab_path=crypttab,
+    )
+    assert crypttab.read_text().splitlines().count(expected_entry) == 1

tests/unit/test_packages.py

@@ -0,0 +1,30 @@
+import pytest
+
+from lim import config, packages
+from lim.errors import LimError
+
+
+@pytest.fixture
+def package_dir(tmp_path, monkeypatch):
+    monkeypatch.setattr(config, "PACKAGE_PATH", tmp_path)
+    return tmp_path
+
+
+def test_strips_comments_and_blank_lines(package_dir):
+    (package_dir / "general.txt").write_text(
+        "# header comment\nnano\ntree# inline comment\n\nhtop\n"
+    )
+    assert packages.get_packages("general") == ["nano", "tree", "htop"]
+
+
+def test_multiple_collections_are_concatenated(package_dir):
+    (package_dir / "a.txt").write_text("one\n")
+    subdir = package_dir / "server"
+    subdir.mkdir()
+    (subdir / "luks.txt").write_text("two\nthree\n")
+    assert packages.get_packages("a", "server/luks") == ["one", "two", "three"]
+
+
+def test_missing_collection_raises(package_dir):
+    with pytest.raises(LimError):
+        packages.get_packages("does-not-exist")

tests/unit/test_raspberry.py

@@ -0,0 +1,72 @@
+import pytest
+
+from lim.device import Device
+from lim.image import raspberry
+from lim.image.session import ImageSession
+
+
+@pytest.fixture
+def session(tmp_path):
+    session = ImageSession(Device("mmcblk0"))
+    session.root_mount_path = tmp_path
+    session.boot_partition_uuid = "BOOT-UUID"
+    return session
+
+
+class TestSeedBootUuid:
+    def test_replaces_mmcblk_reference(self, tmp_path, session):
+        fstab = tmp_path / "etc/fstab"
+        fstab.parent.mkdir()
+        fstab.write_text("/dev/mmcblk0p1  /boot  vfat  defaults  0  0\n")
+        raspberry._seed_boot_uuid(session)
+        assert fstab.read_text() == "UUID=BOOT-UUID  /boot  vfat  defaults  0  0\n"
+
+    def test_skips_partuuid_based_images(self, tmp_path, session):
+        fstab = tmp_path / "etc/fstab"
+        fstab.parent.mkdir()
+        content = "PARTUUID=6c586e13-01  /boot  vfat  defaults  0  0\n"
+        fstab.write_text(content)
+        raspberry._seed_boot_uuid(session)  # must not raise
+        assert fstab.read_text() == content
+
+
+class TestEnsureImageMounted:
+    def test_reads_uuids_when_boot_already_mounted(self, fake_runner):
+        session = ImageSession(Device("sda"))
+        fake_runner.outputs["mount"] = "/dev/sda1 on /tmp/x/boot type vfat (rw)"
+        # Distinct per-partition values so a boot/root swap cannot pass.
+        fake_runner.outputs["/dev/sda1 -s UUID"] = "boot-uuid"
+        fake_runner.outputs["/dev/sda2 -s UUID"] = "root-uuid"
+        fake_runner.outputs["-s TYPE"] = "crypto_LUKS"
+
+        raspberry._ensure_image_mounted(session)
+
+        assert session.boot_partition_uuid == "boot-uuid"
+        assert session.root_partition_uuid == "root-uuid"
+        assert session.root_mapper_name == "linux-image-manager-root-uuid"
+        assert session.root_mapper_path == "/dev/mapper/linux-image-manager-root-uuid"
+
+    def test_plain_root_keeps_partition_as_mapper(self, fake_runner):
+        session = ImageSession(Device("sda"))
+        fake_runner.outputs["mount"] = "/dev/sda1 on /tmp/x/boot type vfat (rw)"
+        fake_runner.outputs["-s UUID"] = "uuid-7"
+        fake_runner.outputs["-s TYPE"] = "ext4"
+
+        raspberry._ensure_image_mounted(session)
+
+        assert session.root_mapper_name is None
+        assert session.root_mapper_path == "/dev/sda2"
+
+    def test_mounts_when_nothing_is_mounted(self, fake_runner, tmp_path):
+        session = ImageSession(Device("sda"))
+        session.boot_mount_path = tmp_path / "boot"
+        session.root_mount_path = tmp_path / "root"
+        fake_runner.outputs["-s TYPE"] = "ext4"
+        fake_runner.outputs["/dev/sda1 -s UUID"] = "boot-uuid"
+        fake_runner.outputs["/dev/sda2 -s UUID"] = "root-uuid"
+
+        raspberry._ensure_image_mounted(session)
+
+        assert len(fake_runner.find("mount", "-v")) == 2
+        assert session.boot_partition_uuid == "boot-uuid"
+        assert session.root_partition_uuid == "root-uuid"

tests/unit/test_runner.py

@@ -0,0 +1,92 @@
+"""Tests against the real runner module (no fake) using harmless commands."""
+
+import subprocess
+
+import pytest
+
+from lim import runner, ui
+from lim.errors import LimError
+
+MISSING = "lim-definitely-missing-binary-x"
+
+
+class TestMissingBinaries:
+    def test_run_raises_lim_error(self):
+        with pytest.raises(LimError, match="Command not found"):
+            runner.run([MISSING])
+
+    def test_run_tolerates_when_check_is_false(self):
+        result = runner.run([MISSING], check=False)
+        assert result.returncode == runner.COMMAND_NOT_FOUND
+
+    def test_output_raises_lim_error(self):
+        with pytest.raises(LimError, match="Command not found"):
+            runner.output([MISSING])
+
+    def test_output_tolerates_when_check_is_false(self):
+        assert runner.output([MISSING], check=False) == ""
+
+    def test_succeeds_returns_false(self):
+        assert runner.succeeds([MISSING]) is False
+
+    def test_tolerated_paths_emit_a_warning(self, monkeypatch):
+        warnings = []
+        monkeypatch.setattr(ui, "warning", warnings.append)
+        runner.run([MISSING], check=False)
+        runner.output([MISSING], check=False)
+        runner.succeeds([MISSING])
+        assert len(warnings) == 3
+        assert all("Command not found" in text for text in warnings)
+
+    def test_pipeline_raises_lim_error(self):
+        with pytest.raises(LimError, match="Command not found"):
+            runner.pipeline(["echo", "x"], [MISSING])
+
+    def test_pipeline_raises_when_first_member_is_missing(self):
+        with pytest.raises(LimError, match=f"Command not found: {MISSING}"):
+            runner.pipeline([MISSING], ["cat"])
+
+    def test_pipeline_reaps_started_members(self, monkeypatch):
+        spawned = []
+        original_popen = subprocess.Popen
+
+        def spying_popen(*args, **kwargs):
+            process = original_popen(*args, **kwargs)
+            spawned.append(process)
+            return process
+
+        monkeypatch.setattr(subprocess, "Popen", spying_popen)
+        with pytest.raises(LimError, match="Command not found"):
+            runner.pipeline(["sleep", "60"], [MISSING])
+        assert len(spawned) == 1
+        assert spawned[0].poll() is not None  # killed and reaped, not running
+        assert spawned[0].stdout.closed
+
+    def test_run_prefers_explicit_error_message(self):
+        with pytest.raises(LimError, match="custom message"):
+            runner.run([MISSING], error_msg="custom message")
+
+    def test_output_prefers_explicit_error_message(self):
+        with pytest.raises(LimError, match="custom message"):
+            runner.output([MISSING], error_msg="custom message")
+
+
+class TestHappyPath:
+    def test_run_returns_completed_process(self):
+        assert runner.run(["true"]).returncode == 0
+
+    def test_run_raises_on_nonzero_exit(self):
+        with pytest.raises(LimError, match="Command failed with code 1"):
+            runner.run(["false"])
+
+    def test_output_returns_stripped_stdout(self):
+        assert runner.output(["echo", "hello"]) == "hello"
+
+    def test_succeeds_reflects_exit_code(self):
+        assert runner.succeeds(["true"]) is True
+        assert runner.succeeds(["false"]) is False
+
+    def test_pipeline_runs_and_checks_every_member(self):
+        runner.pipeline(["echo", "x"], ["cat"])  # must not raise
+        with pytest.raises(LimError, match="Pipeline failed"):
+            runner.pipeline(["false"], ["cat"])

tests/unit/test_storage.py

@@ -0,0 +1,70 @@
+import pytest
+
+from lim import device
+from lim.device import Device
+from lim.storage import raid1, single_drive
+from lim.storage.common import StorageTarget
+
+
+@pytest.fixture
+def block_devices(monkeypatch):
+    monkeypatch.setattr(device, "is_block_device", lambda path: True)
+    monkeypatch.setattr(Device, "optimal_blocksize", property(lambda self: "4K"))
+
+
+def test_storage_target_derives_all_paths():
+    target = StorageTarget(Device("sdb"))
+    assert target.mapper_name == "encrypteddrive-sdb"
+    assert target.mapper_path == "/dev/mapper/encrypteddrive-sdb"
+    assert target.mount_path == "/media/encrypteddrive-sdb"
+    assert target.partition_path == "/dev/sdb1"
+
+
+def test_single_drive_setup_command_sequence(
+    fake_runner, answers, block_devices, monkeypatch
+):
+    monkeypatch.setattr("lim.system.real_user", lambda: "kevin")
+    answers("sdb", "N")  # device name, skip overwrite
+
+    single_drive.setup()
+
+    fdisk_calls = [
+        (cmd, input_text)
+        for kind, cmd, input_text in fake_runner.calls
+        if kind == "run" and cmd[0] == "fdisk"
+    ]
+    assert [input_text for _, input_text in fdisk_calls] == [
+        single_drive.CREATE_GPT_TABLE_INPUT,
+        single_drive.CREATE_PARTITION_INPUT,
+    ]
+    assert len(fake_runner.find("cryptsetup", "-y", "luksFormat", "/dev/sdb1")) == 1
+    assert len(fake_runner.find("cryptsetup", "luksOpen", "encrypteddrive-sdb")) == 1
+    assert len(fake_runner.find("mkfs.btrfs", "/dev/mapper/encrypteddrive-sdb")) == 1
+    assert len(fake_runner.find("mount", "/media/encrypteddrive-sdb")) == 1
+    assert len(fake_runner.find("chown", "kevin:kevin")) == 1
+
+
+def test_single_drive_umount(fake_runner, answers, block_devices):
+    answers("sdb")
+    single_drive.umount()
+    assert len(fake_runner.find("umount", "/dev/mapper/encrypteddrive-sdb")) == 1
+    assert len(fake_runner.find("cryptsetup", "luksClose", "encrypteddrive-sdb")) == 1
+
+
+def test_raid1_setup_uses_both_whole_devices(fake_runner, answers, block_devices):
+    answers("sdb", "sdc")
+    raid1.setup()
+    assert len(fake_runner.find("cryptsetup", "luksFormat", "/dev/sdb")) == 1
+    assert len(fake_runner.find("cryptsetup", "luksFormat", "/dev/sdc")) == 1
+    mkfs = fake_runner.find("mkfs.btrfs", "-m raid1", "-d raid1")
+    assert mkfs == [
+        [
+            "mkfs.btrfs",
+            "-m",
+            "raid1",
+            "-d",
+            "raid1",
+            "/dev/mapper/encrypteddrive-sdb",
+            "/dev/mapper/encrypteddrive-sdc",
+        ]
+    ]

tests/unit/test_sync.py

@@ -0,0 +1,119 @@
+from pathlib import Path
+
+import pytest
+
+from lim import config, system
+from lim.data import sync
+from lim.errors import LimError
+
+
+@pytest.fixture
+def home(tmp_path):
+    home = tmp_path / "home/kevin"
+    (home / ".ssh").mkdir(parents=True)
+    (home / ".ssh/id_rsa").write_text("key")
+    (home / ".gitconfig").write_text("[user]")
+    return home
+
+
+@pytest.fixture
+def data_path(tmp_path):
+    return tmp_path / "decrypted/data"
+
+
+@pytest.fixture
+def backup_folder(tmp_path):
+    return tmp_path / "decrypted/backup/import/20260707000000"
+
+
+def test_import_plan_only_covers_existing_items(home, data_path, backup_folder):
+    operations = sync.build_sync_plan("import", home, data_path, backup_folder)
+    sources = [operation.source for operation in operations]
+    assert sources == [f"{home}/.ssh/", f"{home}/.gitconfig"]
+    for operation in operations:
+        assert operation.destination.startswith(str(data_path))
+
+
+def test_export_swaps_source_and_destination(home, data_path, backup_folder):
+    exported = Path(f"{data_path}{home}/.gitconfig")
+    exported.parent.mkdir(parents=True)
+    exported.write_text("[user]")
+    operations = sync.build_sync_plan("export", home, data_path, backup_folder)
+    assert operations == [
+        sync.SyncOperation(
+            source=str(exported),
+            destination=f"{home}/.gitconfig",
+            backup_dir=str(Path(f"{backup_folder}{home}")),
+            is_directory=False,
+        )
+    ]
+
+
+def test_unknown_mode_raises(home, data_path, backup_folder):
+    with pytest.raises(LimError):
+        sync.build_sync_plan("sideways", home, data_path, backup_folder)
+
+
+def test_rsync_command_uses_delete_only_for_directories():
+    directory_op = sync.SyncOperation("src/", "dst/", "backup", is_directory=True)
+    file_op = sync.SyncOperation("src", "dst", "backup", is_directory=False)
+    assert sync.rsync_command(directory_op) == [
+        "rsync", "-abcEPuvW", "--delete", "--backup-dir=backup", "src/", "dst/"
+    ]
+    assert sync.rsync_command(file_op) == [
+        "rsync", "-abcEPuvW", "--backup-dir=backup", "src", "dst"
+    ]
+
+
+def test_import_syncs_from_real_home(tmp_path, fake_runner, monkeypatch):
+    real_home = tmp_path / "home/kevin"
+    real_home.mkdir(parents=True)
+    (real_home / ".gitconfig").write_text("[user]")
+    monkeypatch.setattr(system, "real_home", lambda: real_home)
+    monkeypatch.setattr(config, "DECRYPTED_PATH", tmp_path / "decrypted")
+    monkeypatch.setattr(config, "DATA_PATH", tmp_path / "decrypted/data")
+    monkeypatch.setattr(config, "BACKUP_PATH", tmp_path / "decrypted/backup")
+    fake_runner.outputs["mount"] = f"encfs on {tmp_path / 'decrypted'} type fuse"
+
+    sync.import_from_system()
+
+    rsync_calls = fake_runner.find("rsync")
+    assert len(rsync_calls) == 1
+    assert rsync_calls[0][-2] == str(real_home / ".gitconfig")
+
+
+def test_export_chowns_real_home_without_sudo(tmp_path, fake_runner, monkeypatch):
+    real_home = tmp_path / "home/kevin"
+    (real_home / ".ssh").mkdir(parents=True)
+    (real_home / ".ssh/id_rsa").write_text("key")
+    monkeypatch.setattr(system, "real_home", lambda: real_home)
+    monkeypatch.setattr(system, "real_user", lambda: "kevin")
+    monkeypatch.setattr(config, "DECRYPTED_PATH", tmp_path / "decrypted")
+    monkeypatch.setattr(config, "DATA_PATH", tmp_path / "decrypted/data")
+    monkeypatch.setattr(config, "BACKUP_PATH", tmp_path / "decrypted/backup")
+    fake_runner.outputs["mount"] = f"encfs on {tmp_path / 'decrypted'} type fuse"
+
+    sync.export_to_system()
+
+    chown_calls = [
+        (cmd, sudo) for cmd, sudo in fake_runner.sudo_log if cmd[0] == "chown"
+    ]
+    assert chown_calls == [
+        (["chown", "-R", "kevin:kevin", str(real_home)], False)
+    ]
+    assert (real_home / ".ssh/id_rsa").stat().st_mode & 0o777 == 0o600
+
+
+def test_execute_sync_plan_creates_folders_and_runs_rsync(
+    tmp_path, fake_runner
+):
+    operation = sync.SyncOperation(
+        source=str(tmp_path / "src.txt"),
+        destination=str(tmp_path / "deep/nested/dst.txt"),
+        backup_dir=str(tmp_path / "backup/deep"),
+        is_directory=False,
+    )
+    sync.execute_sync_plan([operation])
+    assert (tmp_path / "deep/nested").is_dir()
+    assert (tmp_path / "backup/deep").is_dir()
+    assert len(fake_runner.find("rsync", "-abcEPuvW")) == 1

tests/unit/test_verify.py

@@ -0,0 +1,52 @@
+import hashlib
+
+import pytest
+
+from lim.errors import LimError
+from lim.image import verify
+
+CONTENT = b"fake image content"
+
+
+@pytest.fixture
+def image(tmp_path):
+    path = tmp_path / "image.img"
+    path.write_bytes(CONTENT)
+    return path
+
+
+@pytest.mark.parametrize("algorithm", ["md5", "sha1", "sha256", "sha512"])
+def test_matching_checksum_passes(image, algorithm):
+    checksum = hashlib.new(algorithm, CONTENT).hexdigest()
+    verify.verify_checksum(image, checksum)
+
+
+def test_uppercase_checksum_passes(image):
+    checksum = hashlib.sha256(CONTENT).hexdigest().upper()
+    verify.verify_checksum(image, checksum)
+
+
+def test_wrong_checksum_raises(image):
+    checksum = hashlib.sha256(b"other content").hexdigest()
+    with pytest.raises(LimError):
+        verify.verify_checksum(image, checksum)
+
+
+def test_unrecognized_digest_length_raises(image):
+    with pytest.raises(LimError):
+        verify.verify_checksum(image, "abc123")
+
+
+def test_missing_checksum_is_skipped(image):
+    verify.verify_checksum(image, None)  # must not raise
+
+
+def test_resolve_checksum_takes_first_available(fake_runner):
+    fake_runner.success_by_fragment["image.img.sha1"] = False
+    fake_runner.success_by_fragment["image.img.sha512"] = True
+    fake_runner.outputs["-q -O -"] = "deadbeef  image.img"
+    assert verify.resolve_checksum("https://example.org/image.img") == "deadbeef"
+
+
+def test_resolve_checksum_returns_none_without_sources(fake_runner):
+    assert verify.resolve_checksum("https://example.org/image.img") is None