Bump the actions group with 2 updates

Bumps the actions group with 2 updates: [actions/checkout](https://github.com/actions/checkout) and [actions/setup-python](https://github.com/actions/setup-python).


Updates `actions/checkout` from 4 to 7
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v4...v7)

Updates `actions/setup-python` from 5 to 7
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](https://github.com/actions/setup-python/compare/v5...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: actions
- dependency-name: actions/setup-python
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: actions
...

Signed-off-by: dependabot[bot] <support@github.com>

.dockerignore

@@ -0,0 +1,4 @@
+.git
+.ruff_cache
+.pytest_cache
+__pycache__

.github/FUNDING.yml

@@ -0,0 +1,7 @@
+github: kevinveenbirkenbach
+
+patreon: kevinveenbirkenbach
+
+buy_me_a_coffee: kevinveenbirkenbach
+
+custom: https://s.veen.world/paypaldonate

.github/dependabot.yml

@@ -0,0 +1,21 @@
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+    groups:
+      actions:
+        patterns:
+          - "*"
+
+  - package-ecosystem: docker
+    directories:
+      - "/tests/e2e"
+    schedule:
+      interval: weekly
+
+  - package-ecosystem: pip
+    directory: /
+    schedule:
+      interval: weekly

.github/workflows/ci.yml

@@ -0,0 +1,80 @@
+name: CI
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  test-and-lint:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v7
+
+      - name: Set up Python
+        uses: actions/setup-python@v7
+        with:
+          python-version: "3.12"
+          cache: "pip"
+
+      - name: Install package and tooling
+        shell: bash
+        run: |
+          set -euo pipefail
+          python -m pip install --upgrade pip
+          python -m pip install -e .
+          python -m pip install ruff
+
+      - name: Ruff (lint)
+        shell: bash
+        run: |
+          set -euo pipefail
+          ruff check .
+
+      - name: Ruff (format check)
+        shell: bash
+        run: |
+          set -euo pipefail
+          ruff format --check .
+
+      - name: Unit tests
+        shell: bash
+        run: |
+          set -euo pipefail
+          make test-unit
+
+      - name: Integration tests
+        shell: bash
+        run: |
+          set -euo pipefail
+          make test-integration
+
+  docs:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v7
+
+      - name: Markdown and mermaid lint
+        shell: bash
+        run: |
+          set -euo pipefail
+          make lint-docs
+
+  e2e:
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v7
+
+      - name: End-to-end tests in a container
+        shell: bash
+        run: |
+          set -euo pipefail
+          make test-e2e

.github/workflows/codeql.yml

@@ -0,0 +1,43 @@
+name: CodeQL
+
+on:
+  push:
+  pull_request:
+  schedule:
+    - cron: "27 4 * * 1"
+
+jobs:
+  analyze:
+    name: Check security
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+
+    permissions:
+      security-events: write
+      packages: read
+      contents: read
+
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - language: actions
+            build-mode: none
+          - language: python
+            build-mode: none
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v7
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v4
+        with:
+          languages: ${{ matrix.language }}
+          build-mode: ${{ matrix.build-mode }}
+          queries: security-extended,security-and-quality
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v4
+        with:
+          category: "/language:${{ matrix.language }}"

.gitignore

@@ -0,0 +1,8 @@
+__pycache__/
+*.py[cod]
+*.egg-info/
+build/
+dist/
+.pytest_cache/
+.ruff_cache/
+.mypy_cache/

.markdownlint-cli2.jsonc

@@ -0,0 +1,13 @@
+{
+  "config": {
+    "default": true,
+    "MD013": false,
+    "MD033": false,
+    "MD041": false
+  },
+  "ignores": [
+    "node_modules",
+    ".agents",
+    ".claude"
+  ]
+}

CHANGELOG.md

@@ -0,0 +1,6 @@
+# Changelog
+
+## [1.0.0] - 2026-08-14
+
+Official Release🥳
+

LICENSE

@@ -1,661 +0,0 @@
-                    GNU AFFERO GENERAL PUBLIC LICENSE
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-<https://www.gnu.org/licenses/>.

MIRRORS

@@ -0,0 +1,4 @@
+git@github.com:kevinveenbirkenbach/swap-forge.git
+ssh://git@git.veen.world:2201/kevinveenbirkenbach/swap-forge.git
+ssh://git@code.infinito.nexus:2201/kevinveenbirkenbach/swap-forge.git
+https://pypi.org/project/swap-forge/

Makefile

@@ -0,0 +1,50 @@
+SHELL := /usr/bin/env bash
+
+.PHONY: help lint lint-docs format test test-unit test-integration test-e2e clean
+
+PY ?= python3
+E2E_IMAGE ?= swap-forge-e2e
+MD_LINT_IMAGE ?= davidanson/markdownlint-cli2:latest
+MERMAID_IMAGE ?= minlag/mermaid-cli:latest
+
+export PYTHONPATH := $(CURDIR)/src
+
+help:
+	@echo "Targets:"
+	@echo "  make lint             - ruff check + ruff format --check"
+	@echo "  make lint-docs        - markdownlint + mermaid diagram validation"
+	@echo "  make format           - apply ruff format"
+	@echo "  make test             - unit + integration tests"
+	@echo "  make test-unit        - unit tests only"
+	@echo "  make test-integration - integration tests only"
+	@echo "  make test-e2e         - install and exercise the CLI in a container"
+	@echo "  make clean            - remove caches"
+
+lint:
+	ruff check .
+	ruff format --check .
+
+# The repository is mounted read-only: mermaid-cli writes its SVGs next to the
+# output file, which must never land in the working tree.
+lint-docs:
+	docker run --rm -v "$(CURDIR)":/workdir $(MD_LINT_IMAGE) "**/*.md"
+	docker run --rm -v "$(CURDIR)":/data:ro -w /tmp $(MERMAID_IMAGE) -i /data/README.md -o /tmp/out.md
+
+format:
+	ruff format .
+
+test: test-unit test-integration
+
+test-unit:
+	$(PY) -m unittest discover -s tests/unit -t . -p "test_*.py"
+
+test-integration:
+	$(PY) -m unittest discover -s tests/integration -t . -p "test_*.py"
+
+test-e2e:
+	docker build -f tests/e2e/Dockerfile -t $(E2E_IMAGE) .
+	docker run --rm $(E2E_IMAGE)
+
+clean:
+	rm -rf .pytest_cache .ruff_cache .mypy_cache
+	find . -type d -name "__pycache__" -print0 | xargs -0 -r rm -rf

README.md

@@ -1,2 +1,139 @@
-# create-linux-swapfile
+# SwapForge (swap-forge) 🔄
-Creates a linux swapfile
+
+[![GitHub Sponsors](https://img.shields.io/badge/Sponsor-GitHub%20Sponsors-blue?logo=github)](https://github.com/sponsors/kevinveenbirkenbach) [![Patreon](https://img.shields.io/badge/Support-Patreon-orange?logo=patreon)](https://www.patreon.com/c/kevinveenbirkenbach) [![Buy Me a Coffee](https://img.shields.io/badge/Buy%20me%20a%20Coffee-Funding-yellow?logo=buymeacoffee)](https://buymeacoffee.com/kevinveenbirkenbach) [![PayPal](https://img.shields.io/badge/Donate-PayPal-blue?logo=paypal)](https://s.veen.world/paypaldonate)
+
+[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](LICENSE) [![GitHub stars](https://img.shields.io/github/stars/kevinveenbirkenbach/swap-forge.svg?style=social)](https://github.com/kevinveenbirkenbach/swap-forge/stargazers)
+
+SwapForge is a small Python CLI for creating and managing Linux swapfiles. Whether you need to boost system performance or add swap space to your setup, SwapForge automates the process quickly and reliably — and it knows the difference between btrfs and everything else.
+
+---
+
+## 🧭 How it works
+
+```mermaid
+flowchart TD
+    A["swap-forge SIZE"] --> B["parse SIZE into MiB"]
+    B --> B2{"parsable?"}
+    B2 -- no --> X["Invalid size format - exit 1"]
+    B2 -- yes --> C["findmnt -no FSTYPE /"]
+    C --> D{"root filesystem is btrfs?"}
+    D -- yes --> E["target: /var/swap/swapfile"]
+    D -- no --> F["target: /swapfile"]
+    E --> G["read the size of the existing swapfile"]
+    F --> G
+    G --> H{"same size already?"}
+    H -- yes --> Y["Skipping - exit 0"]
+    H -- no --> I{"a swapfile is already there?"}
+    I -- yes --> J["swapoff, delete it, drop its fstab line"]
+    I -- no --> K
+    J --> K{"root filesystem is btrfs?"}
+    K -- yes --> L["chattr +C, turn compression off, allocate with dd"]
+    K -- no --> M["allocate with fallocate"]
+    L --> N["chmod 600"]
+    M --> N
+    N --> O["mkswap"]
+    O --> P["swapon"]
+    P --> Q["append the entry to /etc/fstab"]
+```
+
+The fstab entry is written **after** activation succeeds, so a failed run never leaves a half-written fstab behind.
+
+---
+
+## 🛠 Features
+
+- **Automated Swapfile Creation:** Easily create a swapfile with a specified size.
+- **Btrfs Aware:** Disables copy-on-write and compression on the swap directory and allocates with `dd`; other filesystems use `fallocate`.
+- **FSTAB Integration:** Automatically updates `/etc/fstab` to ensure the swapfile is mounted at boot.
+- **Safety Checks:** Skips creation when a swapfile of the correct size already exists, and recreates it when the size differs.
+- **Simple CLI Interface:** Run the command with a single argument.
+
+---
+
+## 📥 Installation
+
+```bash
+pip install swap-forge
+```
+
+pip is the single supported installation path.
+
+The package installs **two** identical commands: `swap-forge` (primary) and `swafo` (kept for older documentation and scripts).
+
+---
+
+## 🔧 Requirements
+
+- **Python 3.10+** 🐍
+- **root privileges** — the tool writes `/etc/fstab` and activates swap
+- Always required on `PATH`: `findmnt`, `swapoff`, `chmod`, `mkswap`, `swapon`
+- On a **btrfs** root additionally: `chattr`, `btrfs`, `dd`
+- On any **other** root filesystem additionally: `fallocate`
+
+If a required command is missing, the tool exits with code `127` and a one‑line error instead of a traceback.
+
+---
+
+## 🚀 Usage
+
+Run SwapForge by specifying the desired swapfile size. For example, to create a 2G swapfile:
+
+```bash
+sudo swap-forge 2G
+```
+
+Accepted sizes are whole numbers with an optional unit: `2048`, `2048M`, `2048MB`, `64G`, `64GB`. Without a unit the value is read as MiB.
+
+The swapfile location follows the root filesystem:
+
+| Root filesystem | Swapfile |
+| --- | --- |
+| `btrfs` | `/var/swap/swapfile` |
+| anything else | `/swapfile` |
+
+SwapForge compares the existing swapfile against the requested size, skips when they match, and otherwise removes the old one — including its `/etc/fstab` line — before creating the new one.
+
+### Exit codes
+
+| Code | Meaning |
+| --- | --- |
+| `0` | Swapfile is in place, either created or already correct. |
+| `1` | Invalid size argument, or one of the swap commands failed. |
+| `2` | Invalid command line arguments. |
+| `127` | A required command is not installed. |
+
+---
+
+## 🧪 Development
+
+```bash
+make lint              # ruff check + ruff format --check
+make format            # apply ruff format
+make test              # unit + integration tests
+make test-unit
+make test-integration
+make test-e2e          # install the package in a container and exercise the CLI
+```
+
+Tests run against the working tree — the `Makefile` puts `src/` on `PYTHONPATH`, so no install is needed. Every command execution is mocked and `fstab` handling is exercised against a temporary file, so the suite never touches real swap.
+
+---
+
+## 🧑‍💻 Author
+
+Developed by **Kevin Veen-Birkenbach**
+
+- 📧 [kevin@veen.world](mailto:kevin@veen.world)
+- 🌐 [https://www.veen.world](https://www.veen.world)
+
+---
+
+## 📜 License
+
+This project is licensed under the **MIT License**.
+
+---
+
+## 🤝 Contributions
+
+Contributions are welcome! Feel free to fork the repository, submit pull requests, or open issues if you have suggestions or encounter any problems. Let's make Linux swap management easier together! 😊

create-linux-swapfile.sh

@@ -1,14 +0,0 @@
-#!/bin/bash
-FSTAB_SWAP_ENTRY="/swapfile none swap defaults 0 0"
-SWAP_FILE="/swapfile"
-FSTAB_FILE="/etc/fstab"
-if grep -q "$FSTAB_SWAP_ENTRY" "$FSTAB_FILE"; then
-	echo "Skipping creation of swap partion because entry allready exists in \"$FSTAB_FILE\"!"
-else
-	echo "Creating swap partition..." &&
-	sudo fallocate -l "$1" "$SWAP_FILE" &&
-	sudo chmod 600 "$SWAP_FILE" &&
-	sudo mkswap "$SWAP_FILE" &&
-	sudo swapon "$SWAP_FILE" &&
-	sudo sh -c "echo \"$FSTAB_SWAP_ENTRY\">>\"$FSTAB_FILE\"" || exit 1
-fi

pyproject.toml

@@ -0,0 +1,36 @@
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[project]
+name = "swap-forge"
+version = "1.0.0"
+description = "Create, resize and register a Linux swapfile, btrfs aware."
+readme = "README.md"
+requires-python = ">=3.10"
+license = { text = "MIT" }
+authors = [{ name = "Kevin Veen-Birkenbach", email = "kevin@veen.world" }]
+keywords = ["swap", "swapfile", "btrfs", "linux", "cli"]
+dependencies = []
+
+[project.urls]
+Homepage = "https://www.veen.world/"
+Repository = "https://github.com/kevinveenbirkenbach/swap-forge"
+
+[project.scripts]
+swap-forge = "swap_forge.cli:main"
+swafo = "swap_forge.cli:main"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/swap_forge"]
+core-metadata-version = "2.4"
+
+[tool.hatch.build.targets.sdist]
+core-metadata-version = "2.4"
+
+[tool.ruff]
+line-length = 88
+
+[tool.ruff.lint]
+select = ["E", "F", "I", "B", "UP"]
+ignore = ["E501"]

src/swap_forge/__main__.py

@@ -0,0 +1,6 @@
+import sys
+
+from swap_forge.cli import main
+
+if __name__ == "__main__":
+    sys.exit(main())

src/swap_forge/cli.py

@@ -0,0 +1,74 @@
+import argparse
+import sys
+from subprocess import CalledProcessError
+
+from swap_forge.core import (
+    EXIT_COMMAND_FAILED,
+    EXIT_MISSING_BINARY,
+    MissingBinaryError,
+    create_swap,
+    detect_root_fs,
+    get_swap_size,
+    parse_size_to_mib,
+    remove_swap,
+    swap_path_for,
+)
+
+
+def build_parser():
+    """Return the argument parser for the swap-forge command."""
+    parser = argparse.ArgumentParser(description="SwapForge Python edition")
+    parser.add_argument("size", help="Swapfile size (e.g. 2048M or 64G)")
+    return parser
+
+
+def main(argv=None):
+    """Create or resize the system swapfile.
+
+    Args:
+        argv: Argument list, defaults to sys.argv[1:].
+
+    Returns:
+        Process exit code.
+    """
+    args = build_parser().parse_args(argv)
+
+    try:
+        new_size = parse_size_to_mib(args.size)
+    except ValueError as error:
+        print(f"Error: {error}", file=sys.stderr)
+        return 1
+
+    try:
+        fs = detect_root_fs()
+        path = swap_path_for(fs)
+        old_size = get_swap_size(path)
+
+        if old_size == new_size and old_size > 0:
+            print(
+                f"Swapfile {path} already exists with correct size "
+                f"({old_size} MiB). Skipping."
+            )
+            return 0
+
+        if old_size > 0:
+            print(
+                f"Existing swapfile {path} has size {old_size} MiB, "
+                f"expected {new_size} MiB. Recreating..."
+            )
+            remove_swap(path)
+
+        create_swap(path, new_size, fs)
+    except MissingBinaryError as error:
+        print(f"Error: {error}", file=sys.stderr)
+        return EXIT_MISSING_BINARY
+    except CalledProcessError as error:
+        command = error.cmd[0] if isinstance(error.cmd, list | tuple) else error.cmd
+        print(
+            f"Error: '{command}' failed with exit code {error.returncode}",
+            file=sys.stderr,
+        )
+        return EXIT_COMMAND_FAILED
+
+    print("Done.")
+    return 0

src/swap_forge/core.py

@@ -0,0 +1,160 @@
+import re
+import subprocess
+from pathlib import Path
+
+FSTAB_FILE = Path("/etc/fstab")
+BTRFS_SWAP_DIR = Path("/var/swap")
+BTRFS_SWAP_PATH = BTRFS_SWAP_DIR / "swapfile"
+DEFAULT_SWAP_PATH = Path("/swapfile")
+
+SIZE_PATTERN = re.compile(r"^(\d+)([gGmM]?[bB]?)?$")
+MIB_PER_GIB = 1024
+
+REQUIRED_BINARIES = ("findmnt", "swapoff", "chmod", "mkswap", "swapon")
+BTRFS_BINARIES = ("chattr", "btrfs", "dd")
+NON_BTRFS_BINARIES = ("fallocate",)
+EXIT_MISSING_BINARY = 127
+EXIT_COMMAND_FAILED = 1
+
+
+class MissingBinaryError(RuntimeError):
+    """A required external command is not installed.
+
+    Args:
+        binary: Name of the missing executable.
+    """
+
+    def __init__(self, binary):
+        super().__init__(f"required command '{binary}' is not installed")
+        self.binary = binary
+
+
+def run(cmd, check=True, capture=False):
+    """Run a command and return the completed process.
+
+    Args:
+        cmd: Command argument list.
+        check: Raise CalledProcessError when the command fails.
+        capture: Capture stdout and stderr as text.
+    """
+    try:
+        if capture:
+            return subprocess.run(cmd, check=check, capture_output=True, text=True)
+        return subprocess.run(cmd, check=check)
+    except FileNotFoundError as error:
+        raise MissingBinaryError(cmd[0]) from error
+
+
+def detect_root_fs():
+    """Return the filesystem type mounted at /."""
+    return run(["findmnt", "-no", "FSTYPE", "/"], capture=True).stdout.strip()
+
+
+def parse_size_to_mib(size):
+    """Convert a size such as '64G' or '2048M' into MiB.
+
+    Args:
+        size: Size string with an optional G/M unit, defaulting to MiB.
+    """
+    match = SIZE_PATTERN.match(size.strip())
+    if not match:
+        raise ValueError(f"Invalid size format: {size}")
+
+    number, unit = match.groups()
+    unit = (unit or "M").lower()
+
+    if unit in ("g", "gb"):
+        return int(number) * MIB_PER_GIB
+    if unit in ("m", "mb"):
+        return int(number)
+    raise ValueError(f"Unsupported unit: {unit}")
+
+
+def get_swap_size(path):
+    """Return the size of the swapfile in MiB, or 0 when it does not exist.
+
+    Args:
+        path: Path of the swapfile.
+    """
+    if not path.exists():
+        return 0
+    return path.stat().st_size // (1024 * 1024)
+
+
+def swap_fstab_line(path):
+    """Return the fstab line registering the given swapfile."""
+    return f"{path} none swap sw 0 0"
+
+
+def remove_swap(path, fstab=FSTAB_FILE):
+    """Disable the swapfile and drop it plus its fstab entry.
+
+    Args:
+        path: Path of the swapfile.
+        fstab: Path of the fstab file to clean up.
+    """
+    run(["swapoff", str(path)], check=False)
+    if path.exists():
+        path.unlink()
+
+    if not fstab.exists():
+        return
+
+    kept = [
+        line
+        for line in fstab.read_text().splitlines()
+        if not re.search(rf"^{re.escape(str(path))}\s+none\s+swap", line)
+    ]
+    fstab.write_text("\n".join(kept) + "\n")
+
+
+def create_swap(path, size_mib, fs, fstab=FSTAB_FILE):
+    """Create, activate and register a swapfile.
+
+    Args:
+        path: Path of the swapfile.
+        size_mib: Desired size in MiB.
+        fs: Filesystem type of the root mount.
+        fstab: Path of the fstab file to append to.
+    """
+    if fs == "btrfs":
+        print(f"Creating {size_mib} MiB swapfile on btrfs at {path}")
+        path.parent.mkdir(parents=True, exist_ok=True)
+        run(["chattr", "+C", str(path.parent)], check=False)
+        run(
+            [
+                "btrfs",
+                "property",
+                "set",
+                "-ts",
+                str(path.parent),
+                "compression",
+                "none",
+            ],
+            check=False,
+        )
+        run(
+            [
+                "dd",
+                "if=/dev/zero",
+                f"of={path}",
+                "bs=1M",
+                f"count={size_mib}",
+                "status=progress",
+            ]
+        )
+    else:
+        print(f"Creating {size_mib} MiB swapfile on {fs} at {path}")
+        run(["fallocate", "-l", f"{size_mib}M", str(path)])
+
+    run(["chmod", "600", str(path)])
+    run(["mkswap", str(path)])
+    run(["swapon", str(path)])
+
+    with fstab.open("a") as handle:
+        handle.write(swap_fstab_line(path) + "\n")
+
+
+def swap_path_for(fs):
+    """Return the swapfile path matching the given root filesystem type."""
+    return BTRFS_SWAP_PATH if fs == "btrfs" else DEFAULT_SWAP_PATH

tests/e2e/Dockerfile

@@ -0,0 +1,12 @@
+FROM python:3.12-slim
+
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends util-linux e2fsprogs btrfs-progs \
+ && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /src
+COPY . /src
+
+RUN pip install --no-cache-dir .
+
+CMD ["sh", "/src/tests/e2e/run.sh"]

tests/e2e/run.sh

@@ -0,0 +1,103 @@
+#!/bin/sh
+# An unprivileged container cannot activate swap, so the run is expected to fail
+# at mkswap or swapon - which of the two depends on the host's /proc/swaps.
+# Everything before it - findmnt, fallocate, chmod - runs for real.
+set -eu
+
+fail() {
+    echo "FAIL: $1" >&2
+    exit 1
+}
+
+SWAPFORGE="$(command -v swap-forge)" || fail "swap-forge is not on PATH after install"
+echo "ok: swap-forge installed at ${SWAPFORGE}"
+
+command -v swafo >/dev/null || fail "the swafo alias is not on PATH after install"
+echo "ok: swafo alias installed"
+
+case "${SWAPFORGE}" in
+    /usr/local/bin/*) ;;
+    *) fail "swap-forge resolved to ${SWAPFORGE}, outside the install prefix" ;;
+esac
+echo "ok: resolved from the installed package, not the source tree"
+
+for binary in findmnt swapoff chmod mkswap swapon fallocate chattr btrfs dd; do
+    command -v "${binary}" >/dev/null || fail "${binary} is missing from the image"
+done
+echo "ok: every declared binary is present"
+
+swap-forge --help | grep -q "Swapfile size" || fail "--help does not describe the tool"
+echo "ok: --help"
+
+set +e
+swap-forge >/dev/null 2>&1
+status=$?
+set -e
+[ "${status}" -eq 2 ] || fail "a missing size exited ${status}, expected 2"
+echo "ok: a missing size exits 2"
+
+set +e
+output="$(swap-forge 64T 2>&1)"
+status=$?
+set -e
+[ "${status}" -eq 1 ] || fail "an invalid size exited ${status}, expected 1"
+echo "${output}" | grep -q "Invalid size format" || fail "invalid size message wrong"
+if echo "${output}" | grep -q "Traceback"; then
+    fail "an invalid size produced a traceback"
+fi
+echo "ok: an invalid size exits 1 without a traceback"
+
+printf 'UUID=deadbeef / ext4 defaults 0 1\n' >/etc/fstab
+cp /etc/fstab /tmp/fstab.before
+
+set +e
+output="$(swap-forge 8M 2>&1)"
+status=$?
+set -e
+[ "${status}" -eq 1 ] || fail "the blocked activation exited ${status}, expected 1"
+echo "${output}" | grep -q "Creating 8 MiB swapfile" || fail "the creation banner is missing"
+echo "${output}" | grep -qE "'(mkswap|swapon)' failed with exit code" || fail "the blocked activation was not reported cleanly"
+if echo "${output}" | grep -q "Traceback"; then
+    fail "the blocked activation produced a traceback"
+fi
+echo "ok: real fallocate and chmod ran; the blocked activation exits 1 cleanly"
+
+[ -f /swapfile ] || fail "/swapfile was not created"
+size="$(stat -c %s /swapfile)"
+[ "${size}" -eq 8388608 ] || fail "/swapfile is ${size} bytes, expected 8388608"
+echo "ok: /swapfile exists with exactly the requested size"
+
+cmp -s /etc/fstab /tmp/fstab.before || fail "/etc/fstab changed although activation failed"
+echo "ok: /etc/fstab is untouched when activation fails"
+
+set +e
+output="$(swap-forge 8M 2>&1)"
+status=$?
+set -e
+[ "${status}" -eq 0 ] || fail "the idempotent rerun exited ${status}, expected 0"
+echo "${output}" | grep -q "already exists with correct size (8 MiB). Skipping." \
+    || fail "an existing swapfile of the right size was not detected"
+echo "ok: a rerun with the same size is a no-op - the idempotency the role relies on"
+
+set +e
+output="$(swap-forge 12M 2>&1)"
+status=$?
+set -e
+echo "${output}" | grep -q "has size 8 MiB, expected 12 MiB. Recreating..." \
+    || fail "a size change did not trigger a recreation"
+size="$(stat -c %s /swapfile)"
+[ "${size}" -eq 12582912 ] || fail "/swapfile is ${size} bytes after resize, expected 12582912"
+echo "ok: a different size really removes and recreates the swapfile"
+
+cmp -s /etc/fstab /tmp/fstab.before || fail "/etc/fstab changed during the resize cycle"
+echo "ok: /etc/fstab survived the resize cycle byte for byte"
+
+set +e
+output="$(env PATH=/nonexistent-bin "${SWAPFORGE}" 8M 2>&1)"
+status=$?
+set -e
+[ "${status}" -eq 127 ] || fail "missing findmnt exited ${status}, expected 127"
+echo "${output}" | grep -q "required command 'findmnt' is not installed" || fail "missing findmnt message wrong"
+echo "ok: missing findmnt exits 127 with a clean message"
+
+echo "ALL E2E CHECKS PASSED"

tests/integration/test_cli.py

@@ -0,0 +1,62 @@
+import os
+import subprocess
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parents[2]
+SRC_DIR = REPO_ROOT / "src"
+
+
+def run_cli(*args, path=None):
+    """Run 'python -m swap_forge' with the working tree on PYTHONPATH.
+
+    Args:
+        args: Command line arguments for the CLI.
+        path: Replacement PATH, used to hide the findmnt binary.
+    """
+    env = dict(os.environ)
+    env["PYTHONPATH"] = str(SRC_DIR)
+    if path is not None:
+        env["PATH"] = str(path)
+    return subprocess.run(
+        [sys.executable, "-m", "swap_forge", *args],
+        capture_output=True,
+        text=True,
+        env=env,
+        check=False,
+    )
+
+
+class TestCli(unittest.TestCase):
+    def test_help_exits_zero(self):
+        result = run_cli("--help")
+
+        self.assertEqual(result.returncode, 0, result.stderr)
+        self.assertIn("Swapfile size", result.stdout)
+
+    def test_missing_size_is_rejected(self):
+        result = run_cli()
+
+        self.assertEqual(result.returncode, 2)
+        self.assertIn("size", result.stderr)
+
+    def test_missing_findmnt_fails_cleanly(self):
+        with tempfile.TemporaryDirectory() as empty:
+            result = run_cli("2048M", path=empty)
+
+        self.assertEqual(result.returncode, 127)
+        self.assertIn("required command 'findmnt' is not installed", result.stderr)
+        self.assertNotIn("Traceback", result.stderr)
+
+    def test_invalid_size_fails_without_a_traceback(self):
+        result = run_cli("64T")
+
+        self.assertEqual(result.returncode, 1)
+        self.assertIn("Invalid size format", result.stderr)
+        self.assertNotIn("Traceback", result.stderr)
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/unit/test_cli.py

@@ -0,0 +1,63 @@
+import unittest
+from pathlib import Path
+from subprocess import CalledProcessError
+from unittest import mock
+
+from swap_forge.cli import main
+
+
+class TestMain(unittest.TestCase):
+    def _run(self, argv, fs="ext4", old_size=0):
+        with (
+            mock.patch("swap_forge.cli.detect_root_fs", return_value=fs),
+            mock.patch("swap_forge.cli.swap_path_for", return_value=Path("/swapfile")),
+            mock.patch("swap_forge.cli.get_swap_size", return_value=old_size),
+            mock.patch("swap_forge.cli.remove_swap") as remove,
+            mock.patch("swap_forge.cli.create_swap") as create,
+        ):
+            exit_code = main(argv)
+        return exit_code, remove, create
+
+    def test_creates_a_missing_swapfile(self):
+        exit_code, remove, create = self._run(["2048M"])
+
+        remove.assert_not_called()
+        create.assert_called_once_with(Path("/swapfile"), 2048, "ext4")
+        self.assertEqual(exit_code, 0)
+
+    def test_matching_size_is_left_alone(self):
+        exit_code, remove, create = self._run(["2048M"], old_size=2048)
+
+        remove.assert_not_called()
+        create.assert_not_called()
+        self.assertEqual(exit_code, 0)
+
+    def test_wrong_size_is_recreated(self):
+        exit_code, remove, create = self._run(["4G"], old_size=2048)
+
+        remove.assert_called_once_with(Path("/swapfile"))
+        create.assert_called_once_with(Path("/swapfile"), 4096, "ext4")
+        self.assertEqual(exit_code, 0)
+
+    def test_failing_command_reports_cleanly(self):
+        with (
+            mock.patch("swap_forge.cli.detect_root_fs", return_value="ext4"),
+            mock.patch("swap_forge.cli.swap_path_for", return_value=Path("/swapfile")),
+            mock.patch("swap_forge.cli.get_swap_size", return_value=0),
+            mock.patch("swap_forge.cli.create_swap") as create,
+        ):
+            create.side_effect = CalledProcessError(255, ["swapon", "/swapfile"])
+            exit_code = main(["2048M"])
+
+        self.assertEqual(exit_code, 1)
+
+    def test_invalid_size_exits_non_zero(self):
+        with mock.patch("swap_forge.cli.detect_root_fs") as detect:
+            exit_code = main(["64T"])
+
+        detect.assert_not_called()
+        self.assertEqual(exit_code, 1)
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/unit/test_core.py

@@ -0,0 +1,173 @@
+import tempfile
+import unittest
+from pathlib import Path
+from unittest import mock
+
+from swap_forge.core import (
+    BTRFS_BINARIES,
+    BTRFS_SWAP_PATH,
+    DEFAULT_SWAP_PATH,
+    NON_BTRFS_BINARIES,
+    REQUIRED_BINARIES,
+    MissingBinaryError,
+    create_swap,
+    get_swap_size,
+    parse_size_to_mib,
+    remove_swap,
+    run,
+    swap_fstab_line,
+    swap_path_for,
+)
+
+
+class TestRequiredBinaries(unittest.TestCase):
+    def test_declares_every_external_command_the_package_calls(self):
+        declared = (
+            set(REQUIRED_BINARIES) | set(BTRFS_BINARIES) | set(NON_BTRFS_BINARIES)
+        )
+
+        self.assertEqual(
+            declared,
+            {
+                "findmnt",
+                "swapoff",
+                "chmod",
+                "mkswap",
+                "swapon",
+                "chattr",
+                "btrfs",
+                "dd",
+                "fallocate",
+            },
+        )
+
+    def test_filesystem_specific_binaries_are_not_declared_as_always_required(self):
+        self.assertFalse(set(REQUIRED_BINARIES) & set(BTRFS_BINARIES))
+        self.assertFalse(set(REQUIRED_BINARIES) & set(NON_BTRFS_BINARIES))
+
+    def test_missing_binary_is_reported_with_its_name(self):
+        with mock.patch("swap_forge.core.subprocess.run") as subprocess_run:
+            subprocess_run.side_effect = FileNotFoundError
+
+            with self.assertRaises(MissingBinaryError) as caught:
+                run(["mkswap", "/swapfile"])
+
+        self.assertEqual(caught.exception.binary, "mkswap")
+
+
+class TestParseSizeToMib(unittest.TestCase):
+    def test_gibibytes(self):
+        for value in ("64G", "64g", "64GB", " 64G "):
+            with self.subTest(value=value):
+                self.assertEqual(parse_size_to_mib(value), 65536)
+
+    def test_mebibytes(self):
+        for value in ("2048M", "2048m", "2048MB"):
+            with self.subTest(value=value):
+                self.assertEqual(parse_size_to_mib(value), 2048)
+
+    def test_bare_number_is_mebibytes(self):
+        self.assertEqual(parse_size_to_mib("512"), 512)
+
+    def test_invalid_format(self):
+        for value in ("", "abc", "64T", "-5G", "6.5G"):
+            with self.subTest(value=value), self.assertRaises(ValueError):
+                parse_size_to_mib(value)
+
+    def test_unsupported_unit(self):
+        with self.assertRaises(ValueError):
+            parse_size_to_mib("64b")
+
+
+class TestSwapPathFor(unittest.TestCase):
+    def test_btrfs_uses_the_dedicated_subvolume_path(self):
+        self.assertEqual(swap_path_for("btrfs"), BTRFS_SWAP_PATH)
+
+    def test_other_filesystems_use_the_root_swapfile(self):
+        self.assertEqual(swap_path_for("ext4"), DEFAULT_SWAP_PATH)
+
+
+class TestGetSwapSize(unittest.TestCase):
+    def test_missing_file_is_zero(self):
+        self.assertEqual(get_swap_size(Path("/nonexistent/swapfile")), 0)
+
+    def test_reports_size_in_mebibytes(self):
+        with tempfile.TemporaryDirectory() as base:
+            path = Path(base) / "swapfile"
+            path.write_bytes(b"\0" * (3 * 1024 * 1024))
+
+            self.assertEqual(get_swap_size(path), 3)
+
+
+class TestSwapFstabLine(unittest.TestCase):
+    def test_line_shape(self):
+        self.assertEqual(
+            swap_fstab_line(Path("/swapfile")), "/swapfile none swap sw 0 0"
+        )
+
+
+class TestRemoveSwap(unittest.TestCase):
+    def test_drops_file_and_fstab_entry(self):
+        with tempfile.TemporaryDirectory() as base:
+            swapfile = Path(base) / "swapfile"
+            swapfile.write_bytes(b"\0")
+            fstab = Path(base) / "fstab"
+            fstab.write_text(
+                f"UUID=abc / ext4 defaults 0 1\n{swapfile} none swap sw 0 0\n"
+            )
+
+            with mock.patch("swap_forge.core.run"):
+                remove_swap(swapfile, fstab=fstab)
+
+            self.assertFalse(swapfile.exists())
+            self.assertEqual(fstab.read_text(), "UUID=abc / ext4 defaults 0 1\n")
+
+    def test_keeps_unrelated_fstab_entries(self):
+        with tempfile.TemporaryDirectory() as base:
+            swapfile = Path(base) / "swapfile"
+            fstab = Path(base) / "fstab"
+            fstab.write_text("/other none swap sw 0 0\n")
+
+            with mock.patch("swap_forge.core.run"):
+                remove_swap(swapfile, fstab=fstab)
+
+            self.assertEqual(fstab.read_text(), "/other none swap sw 0 0\n")
+
+    def test_missing_fstab_is_tolerated(self):
+        with tempfile.TemporaryDirectory() as base:
+            with mock.patch("swap_forge.core.run"):
+                remove_swap(Path(base) / "swapfile", fstab=Path(base) / "fstab")
+
+
+class TestCreateSwap(unittest.TestCase):
+    def test_non_btrfs_uses_fallocate_and_appends_to_fstab(self):
+        with tempfile.TemporaryDirectory() as base:
+            swapfile = Path(base) / "swapfile"
+            fstab = Path(base) / "fstab"
+            fstab.write_text("")
+
+            with mock.patch("swap_forge.core.run") as run:
+                create_swap(swapfile, 2048, "ext4", fstab=fstab)
+
+            commands = [call.args[0][0] for call in run.call_args_list]
+            self.assertEqual(commands, ["fallocate", "chmod", "mkswap", "swapon"])
+            self.assertEqual(fstab.read_text(), f"{swapfile} none swap sw 0 0\n")
+
+    def test_btrfs_disables_copy_on_write_and_uses_dd(self):
+        with tempfile.TemporaryDirectory() as base:
+            swapfile = Path(base) / "swap" / "swapfile"
+            fstab = Path(base) / "fstab"
+            fstab.write_text("")
+
+            with mock.patch("swap_forge.core.run") as run:
+                create_swap(swapfile, 1024, "btrfs", fstab=fstab)
+
+            commands = [call.args[0][0] for call in run.call_args_list]
+            self.assertEqual(
+                commands, ["chattr", "btrfs", "dd", "chmod", "mkswap", "swapon"]
+            )
+            self.assertTrue(swapfile.parent.is_dir())
+
+
+if __name__ == "__main__":
+    unittest.main()