diff --git a/.github/workflows/test-cells-conda.yml b/.github/workflows/test-cells-conda.yml
index ea00a4a..5eae81e 100644
--- a/.github/workflows/test-cells-conda.yml
+++ b/.github/workflows/test-cells-conda.yml
@@ -2,6 +2,9 @@ name: test-cells-conda
 
 on:
   workflow_dispatch:
+  push:
+    branches:
+      - develop
   pull_request:
     branches:
       - "**"
diff --git a/.github/workflows/test-cells-ubuntu.yml b/.github/workflows/test-cells-ubuntu.yml
index 4728de9..d1c1ded 100644
--- a/.github/workflows/test-cells-ubuntu.yml
+++ b/.github/workflows/test-cells-ubuntu.yml
@@ -2,6 +2,9 @@ name: test-cells-ubuntu
 
 on:
   workflow_dispatch:
+  push:
+    branches:
+      - develop
   pull_request:
     branches:
       - "**"
diff --git a/.github/workflows/test-shapes-pip.yml b/.github/workflows/test-shapes-pip.yml
index bfb13b9..244450f 100644
--- a/.github/workflows/test-shapes-pip.yml
+++ b/.github/workflows/test-shapes-pip.yml
@@ -2,6 +2,9 @@ name: test-shapes-pip
 
 on:
   workflow_dispatch:
+  push:
+    branches:
+      - develop
   pull_request:
     branches:
       - "**"
diff --git a/.github/workflows/test-style.yml b/.github/workflows/test-style.yml
index 47d8455..8648201 100644
--- a/.github/workflows/test-style.yml
+++ b/.github/workflows/test-style.yml
@@ -2,6 +2,9 @@ name: test-style
 
 on:
   workflow_dispatch:
+  push:
+    branches:
+      - develop
   pull_request:
     branches:
       - "**"
diff --git a/.github/workflows/test-unit.yml b/.github/workflows/test-unit.yml
new file mode 100644
index 0000000..ff571da
--- /dev/null
+++ b/.github/workflows/test-unit.yml
@@ -0,0 +1,35 @@
+name: test-unit
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - develop
+  pull_request:
+    branches:
+      - "**"
+
+concurrency:
+  group: test-unit-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test-unit:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Setup Python
+        uses: actions/setup-python@v6
+        with:
+          python-version: "3.12"
+
+      - name: Install cppwg
+        run: |
+          python3 -m pip install --upgrade pip
+          python3 -m pip install .[dev]
+
+      - name: Run unit tests
+        run: python3 -m pytest tests/
diff --git a/README.md b/README.md
index 6069764..0473380 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,4 @@
+![unit](https://github.com/Chaste/cppwg/actions/workflows/test-unit.yml/badge.svg?branch=develop)
 ![pip](https://github.com/Chaste/cppwg/actions/workflows/test-shapes-pip.yml/badge.svg?branch=develop)
 ![ubuntu](https://github.com/Chaste/cppwg/actions/workflows/test-cells-ubuntu.yml/badge.svg?branch=develop)
 ![conda](https://github.com/Chaste/cppwg/actions/workflows/test-cells-conda.yml/badge.svg?branch=develop)
@@ -51,6 +52,7 @@ options:
                         --castxml_cflags="-Wno-deprecated".
   -i, --includes [INCLUDES ...]
                         List of paths to include directories.
+  --overwrite           Force rewrite of all wrapper files, even if unchanged.
   -q, --quiet           Disable informational messages.
   -l, --logfile [LOGFILE]
                         Output log messages to a file.
@@ -157,6 +159,9 @@ r = Rectangle(4, 5)
 ## Tips
 
 - Use `examples/shapes` or `examples/cells` as a starting point.
+- By default, cppwg only rewrites wrapper files whose content has changed, leaving
+  unchanged files untouched so build systems skip recompiling them. Pass
+  `--overwrite` to force a full rewrite of all wrapper files.
 - To pass extra flags to the castxml clang frontend (e.g. to silence a
   diagnostic), use `--castxml_cflags`. Values starting with `-` must use `=`,
   e.g. `--castxml_cflags="-Wno-deprecated"`.
diff --git a/cppwg/__main__.py b/cppwg/__main__.py
index e2a9a49..439fa8f 100644
--- a/cppwg/__main__.py
+++ b/cppwg/__main__.py
@@ -77,6 +77,13 @@ def parse_args() -> argparse.Namespace:
         help="List of paths to include directories.",
     )
 
+    parser.add_argument(
+        "--overwrite",
+        action="store_true",
+        help="Force rewrite of all wrapper files, even if unchanged. By default, "
+        "unchanged wrapper files are left untouched to speed up rebuilds.",
+    )
+
     parser.add_argument(
         "-q",
         "--quiet",
@@ -143,6 +150,7 @@ def generate(args: argparse.Namespace) -> None:
         castxml_binary=args.castxml_binary,
         castxml_cflags=castxml_cflags or None,
         castxml_compiler=args.castxml_compiler,
+        overwrite=args.overwrite,
     )
 
     generator.generate()
diff --git a/cppwg/generators.py b/cppwg/generators.py
index 5b9b23d..af267e6 100644
--- a/cppwg/generators.py
+++ b/cppwg/generators.py
@@ -49,6 +49,8 @@ class CppWrapperGenerator:
         The namespace containing C++ declarations parsed from the source tree
     package_info : PackageInfo
         A data structure containing the information parsed from package_info_path
+    overwrite : bool
+        Force rewrite of all wrapper files, even if unchanged; defaults to False
     """
 
     def __init__(
@@ -60,9 +62,13 @@ def __init__(
         package_info_path: Optional[str] = None,
         castxml_cflags: Optional[str] = None,
         castxml_compiler: Optional[str] = None,
+        overwrite: bool = False,
     ):
         logger = logging.getLogger()
 
+        # Whether to force rewriting wrapper files that are unchanged
+        self.overwrite: bool = overwrite
+
         logger.info(f"cppwg version {cppwg_version}")
 
         # Check that castxml_binary exists and is executable
@@ -254,6 +260,7 @@ def write_header_collection(self) -> None:
             self.package_info,
             self.wrapper_root,
             self.header_collection_filepath,
+            self.overwrite,
         )
         header_collection_writer.write()
 
@@ -262,7 +269,10 @@ def write_wrappers(self) -> None:
         Write the wrapper code for the package.
         """
         package_writer = CppPackageWrapperWriter(
-            self.package_info, wrapper_templates.template_collection, self.wrapper_root
+            self.package_info,
+            wrapper_templates.template_collection,
+            self.wrapper_root,
+            self.overwrite,
         )
         package_writer.write()
 
diff --git a/cppwg/utils/utils.py b/cppwg/utils/utils.py
index 1a6e379..a5b0e13 100644
--- a/cppwg/utils/utils.py
+++ b/cppwg/utils/utils.py
@@ -1,6 +1,7 @@
 """Utility functions for the cppwg package."""
 
 import ast
+import os
 import re
 from numbers import Number
 from typing import Any, List, Tuple
@@ -8,6 +9,38 @@
 from cppwg.utils.constants import CPPWG_ALL_STRING, CPPWG_TRUE_STRINGS
 
 
+def write_file_if_changed(filepath: str, content: str, overwrite: bool = False) -> bool:
+    """
+    Write content to filepath unless an identical file already exists.
+
+    Skipping unchanged files leaves their modification time intact so that
+    downstream build systems (e.g. make) do not needlessly recompile them.
+
+    Parameters
+    ----------
+    filepath : str
+        The path of the file to write.
+    content : str
+        The content to write to the file.
+    overwrite : bool
+        If True, always write the file even if its content is unchanged.
+
+    Returns
+    -------
+    bool
+        True if the file was written, False if it was skipped as unchanged.
+    """
+    if not overwrite and os.path.isfile(filepath):
+        with open(filepath, "r") as in_file:
+            if in_file.read() == content:
+                return False
+
+    with open(filepath, "w") as out_file:
+        out_file.write(content)
+
+    return True
+
+
 def convert_to_bool(value: Any) -> bool:
     """
     Convert value to a boolean.
diff --git a/cppwg/writers/class_writer.py b/cppwg/writers/class_writer.py
index e344665..8604169 100644
--- a/cppwg/writers/class_writer.py
+++ b/cppwg/writers/class_writer.py
@@ -12,6 +12,7 @@
     CPPWG_EXT,
     CPPWG_HEADER_COLLECTION_FILENAME,
 )
+from cppwg.utils.utils import write_file_if_changed
 from cppwg.writers.base_writer import CppBaseWrapperWriter
 from cppwg.writers.constructor_writer import CppConstructorWrapperWriter
 from cppwg.writers.method_writer import CppMethodWrapperWriter
@@ -29,6 +30,8 @@ class CppClassWrapperWriter(CppBaseWrapperWriter):
         String templates with placeholders for generating wrapper code
     module_classes : Dict[pygccxml.declarations.class_t, str]
         A dictionary of decls and names for all classes in the module
+    overwrite : bool
+        Force rewrite of the class wrapper files, even if unchanged
     has_shared_ptr : bool
         Whether the class uses shared pointers
     hpp_string : str
@@ -42,6 +45,7 @@ def __init__(
         class_info: "CppClassInfo",  # noqa: F821
         wrapper_templates: Dict[str, str],
         module_classes: Dict["class_t", str],  # noqa: F821
+        overwrite: bool = False,
     ) -> None:
         logger = logging.getLogger()
 
@@ -55,6 +59,8 @@ def __init__(
 
         self.module_classes = module_classes
 
+        self.overwrite = overwrite
+
         self.has_shared_ptr: bool = True
 
         self.hpp_string: str = ""
@@ -389,8 +395,5 @@ def write_files(self, work_dir: str, class_py_name: str) -> None:
         hpp_filepath = os.path.join(work_dir, f"{class_py_name}.{CPPWG_EXT}.hpp")
         cpp_filepath = os.path.join(work_dir, f"{class_py_name}.{CPPWG_EXT}.cpp")
 
-        with open(hpp_filepath, "w") as hpp_file:
-            hpp_file.write(self.hpp_string)
-
-        with open(cpp_filepath, "w") as cpp_file:
-            cpp_file.write(self.cpp_string)
+        write_file_if_changed(hpp_filepath, self.hpp_string, self.overwrite)
+        write_file_if_changed(cpp_filepath, self.cpp_string, self.overwrite)
diff --git a/cppwg/writers/header_collection_writer.py b/cppwg/writers/header_collection_writer.py
index 61bb278..50efea5 100644
--- a/cppwg/writers/header_collection_writer.py
+++ b/cppwg/writers/header_collection_writer.py
@@ -6,6 +6,7 @@
 from cppwg.info.class_info import CppClassInfo
 from cppwg.info.free_function_info import CppFreeFunctionInfo
 from cppwg.info.package_info import PackageInfo
+from cppwg.utils.utils import write_file_if_changed
 
 
 class CppHeaderCollectionWriter:
@@ -25,6 +26,8 @@ class CppHeaderCollectionWriter:
             The output directory for the generated wrapper code
         hpp_collection_file : str
             The path to save the header collection file to
+        overwrite : bool
+            Force rewrite of the header collection file, even if unchanged
         hpp_collection : str
             The output string that gets written to the header collection file
         class_dict : Dict[str, CppClassInfo]
@@ -38,10 +41,12 @@ def __init__(
         package_info: PackageInfo,
         wrapper_root: str,
         hpp_collection_file: str,
+        overwrite: bool = False,
     ):
         self.package_info: PackageInfo = package_info
         self.wrapper_root: str = wrapper_root
         self.hpp_collection_file: str = hpp_collection_file
+        self.overwrite: bool = overwrite
         self.hpp_collection: str = ""
 
         # For convenience, collect all class and free function info into dicts keyed by name
@@ -150,5 +155,6 @@ def write(self) -> None:
         self.hpp_collection += f"\n#endif // {self.package_info.name}_HEADERS_HPP_\n"
 
         # Write the header collection string to file
-        with open(self.hpp_collection_file, "w") as hpp_file:
-            hpp_file.write(self.hpp_collection)
+        write_file_if_changed(
+            self.hpp_collection_file, self.hpp_collection, self.overwrite
+        )
diff --git a/cppwg/writers/module_writer.py b/cppwg/writers/module_writer.py
index 269a9c8..c817217 100644
--- a/cppwg/writers/module_writer.py
+++ b/cppwg/writers/module_writer.py
@@ -5,6 +5,7 @@
 from typing import Dict
 
 from cppwg.utils.constants import CPPWG_EXT, CPPWG_HEADER_COLLECTION_FILENAME
+from cppwg.utils.utils import write_file_if_changed
 from cppwg.writers.class_writer import CppClassWrapperWriter
 from cppwg.writers.free_function_writer import CppFreeFunctionWrapperWriter
 
@@ -26,6 +27,8 @@ class CppModuleWrapperWriter:
         String templates with placeholders for generating wrapper code
     wrapper_root : str
         The output directory for the generated wrapper code
+    overwrite : bool
+        Force rewrite of all wrapper files, even if unchanged
 
     classes : Dict[pygccxml.declarations.class_t, str]
         A dictionary of decls and names for all classes to be wrapped in the module
@@ -36,10 +39,12 @@ def __init__(
         module_info: "ModuleInfo",  # noqa: F821
         wrapper_templates: Dict[str, str],
         wrapper_root: str,
+        overwrite: bool = False,
     ):
         self.module_info: "ModuleInfo" = module_info  # noqa: F821
         self.wrapper_templates: Dict[str, str] = wrapper_templates
         self.wrapper_root: str = wrapper_root
+        self.overwrite: bool = overwrite
 
         # For convenience, store a dictionary of decl->name pairs for all
         # classes to be wrapped in the module
@@ -146,8 +151,7 @@ def write_module_wrapper(self) -> None:
             module_dir, f"{full_module_name}.main.{CPPWG_EXT}.cpp"
         )
 
-        with open(module_cpp_file, "w") as out_file:
-            out_file.write(cpp_string)
+        write_file_if_changed(module_cpp_file, cpp_string, self.overwrite)
 
     def write_class_wrappers(self) -> None:
         """Write wrappers for classes in the module."""
@@ -165,6 +169,7 @@ def write_class_wrappers(self) -> None:
                 class_info,
                 self.wrapper_templates,
                 self.classes,
+                self.overwrite,
             )
 
             # Write the class wrappers into /path/to/wrapper_root/modulename/
diff --git a/cppwg/writers/package_writer.py b/cppwg/writers/package_writer.py
index 229a9cc..d31ad53 100644
--- a/cppwg/writers/package_writer.py
+++ b/cppwg/writers/package_writer.py
@@ -17,6 +17,8 @@ class CppPackageWrapperWriter:
         String templates with placeholders for generating wrapper code
     wrapper_root : str
         The output directory for the generated wrapper code
+    overwrite : bool
+        Force rewrite of all wrapper files, even if unchanged
     """
 
     def __init__(
@@ -24,10 +26,12 @@ def __init__(
         package_info: "PackageInfo",  # noqa: F821
         wrapper_templates: Dict[str, str],
         wrapper_root: str,
+        overwrite: bool = False,
     ):
         self.package_info = package_info
         self.wrapper_templates = wrapper_templates
         self.wrapper_root = wrapper_root
+        self.overwrite = overwrite
 
     def write(self) -> None:
         """
@@ -38,5 +42,6 @@ def write(self) -> None:
                 module_info,
                 self.wrapper_templates,
                 self.wrapper_root,
+                self.overwrite,
             )
             module_writer.write()
diff --git a/examples/cells/conda/variants/python3.8.yaml b/examples/cells/conda/variants/python3.8.yaml
deleted file mode 100644
index b34e9cc..0000000
--- a/examples/cells/conda/variants/python3.8.yaml
+++ /dev/null
@@ -1,2 +0,0 @@
-python:
-  - 3.8.*
diff --git a/examples/cells/conda/variants/python3.9.yaml b/examples/cells/conda/variants/python3.9.yaml
deleted file mode 100644
index f305cf2..0000000
--- a/examples/cells/conda/variants/python3.9.yaml
+++ /dev/null
@@ -1,2 +0,0 @@
-python:
-  - 3.9.*
diff --git a/examples/cells/pyproject.toml b/examples/cells/pyproject.toml
index 3b7db8c..2ef295d 100644
--- a/examples/cells/pyproject.toml
+++ b/examples/cells/pyproject.toml
@@ -6,7 +6,7 @@ build-backend = "scikit_build_core.build"
 name = "pycells"
 version = "0.0.1"
 license = { text = "BSD-3-Clause License" }
-requires-python = ">=3.8"
+requires-python = ">=3.10"
 
 [tool.scikit-build]
 cmake.build-type = "Release"
diff --git a/pyproject.toml b/pyproject.toml
index b874398..c9b75be 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,8 +1,66 @@
 [build-system]
-requires = ["setuptools", "wheel"]
+requires = ["setuptools>=61.0"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "cppwg"
+version = "0.3.4"
+description = "An automatic Python wrapper generator for C++ code"
+readme = "README.md"
+requires-python = ">=3.10"
+license = {text = "BSD-3-Clause"}
+keywords = ["C++", "Python", "pybind11"]
+authors = [
+    {name = "Chaste Developers", email = "chaste-users@maillist.ox.ac.uk"},
+]
+classifiers = [
+    "Development Status :: 4 - Beta",
+    "Environment :: Console",
+    "Intended Audience :: Developers",
+    "Operating System :: MacOS :: MacOS X",
+    "Operating System :: Microsoft :: Windows",
+    "Operating System :: POSIX",
+    "Programming Language :: Python :: 3.10",
+    "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
+    "Programming Language :: Python :: Implementation :: CPython",
+    "Topic :: Software Development",
+]
+dependencies = [
+    "pyyaml>=6.0",
+    "pygccxml>=2.2",
+]
+
+[project.optional-dependencies]
+dev = [
+    "black",
+    "flake8",
+    "flake8-bugbear",
+    "flake8-docstrings",
+    "isort",
+    "pytest",
+]
+docs = [
+    "sphinx",
+    "sphinx-rtd-theme",
+    "numpydoc",
+]
+
+[project.scripts]
+cppwg = "cppwg.__main__:main"
+
+[project.urls]
+"Source Code" = "https://github.com/Chaste/cppwg/"
+
+[tool.setuptools]
+zip-safe = false
+
+[tool.setuptools.packages.find]
+include = ["cppwg*"]
 
 [tool.black]
-target-version = ["py38", "py39", "py310", "py311", "py312"]
+target-version = ["py310", "py311", "py312", "py313"]
 extend-exclude = """
 (
   ^/cppwg/templates/
diff --git a/setup.cfg b/setup.cfg
deleted file mode 100644
index 908756c..0000000
--- a/setup.cfg
+++ /dev/null
@@ -1,51 +0,0 @@
-[metadata]
-name = cppwg
-version = 0.3.4
-author = Chaste Developers
-author_email = chaste-users@maillist.ox.ac.uk
-description = An automatic Python wrapper generator for C++ code
-long_description = file: README.md
-keywords = C++, Python, pybind11
-license = BSD-3-Clause
-classifiers =
-    Development Status :: 4 - Beta
-    Environment :: Console
-    Intended Audience :: Developers
-    Operating System :: MacOS :: MacOS X
-    Operating System :: Microsoft :: Windows
-    Operating System :: POSIX
-    Programming Language :: Python :: 3.8
-    Programming Language :: Python :: 3.9
-    Programming Language :: Python :: 3.10
-    Programming Language :: Python :: 3.11
-    Programming Language :: Python :: 3.12
-    Programming Language :: Python :: Implementation :: CPython
-    Topic :: Software Development
-
-project_urls =
-    Source Code = https://github.com/Chaste/cppwg/
-
-[options]
-zip_safe = False
-packages = find:
-python_requires = >=3.8
-install_requires =
-    pyyaml>=6.0
-    pygccxml>=2.2
-
-[options.entry_points]
-console_scripts =
-    cppwg = cppwg.__main__:main
-
-[options.extras_require]
-dev =
-    black
-    flake8
-    flake8-bugbear
-    flake8-docstrings
-    isort
-
-docs =
-    sphinx
-    sphinx-rtd-theme
-    numpydoc
diff --git a/setup.py b/setup.py
deleted file mode 100644
index 685c789..0000000
--- a/setup.py
+++ /dev/null
@@ -1,5 +0,0 @@
-"""Setup."""
-
-from setuptools import setup
-
-setup()
diff --git a/tests/test_utils.py b/tests/test_utils.py
new file mode 100644
index 0000000..505332c
--- /dev/null
+++ b/tests/test_utils.py
@@ -0,0 +1,63 @@
+"""Unit tests for cppwg.utils.utils."""
+
+import os
+
+from cppwg.utils.utils import write_file_if_changed
+
+
+def test_writes_when_file_missing(tmp_path):
+    """A new file is created and reports that it was written."""
+    filepath = os.path.join(tmp_path, "wrapper.cpp")
+
+    wrote = write_file_if_changed(filepath, "content")
+
+    assert wrote is True
+    assert os.path.isfile(filepath)
+    with open(filepath) as f:
+        assert f.read() == "content"
+
+
+def test_skips_when_content_unchanged(tmp_path):
+    """An identical file is left untouched, preserving its mtime."""
+    filepath = os.path.join(tmp_path, "wrapper.cpp")
+    with open(filepath, "w") as f:
+        f.write("content")
+
+    # Backdate the mtime so any rewrite would be detectable
+    old_time = os.path.getmtime(filepath) - 100
+    os.utime(filepath, (old_time, old_time))
+    old_time_ns = os.stat(filepath).st_mtime_ns
+
+    wrote = write_file_if_changed(filepath, "content")
+
+    assert wrote is False
+    assert os.stat(filepath).st_mtime_ns == old_time_ns
+
+
+def test_rewrites_when_content_changed(tmp_path):
+    """A file with different content is rewritten."""
+    filepath = os.path.join(tmp_path, "wrapper.cpp")
+    with open(filepath, "w") as f:
+        f.write("old content")
+
+    wrote = write_file_if_changed(filepath, "new content")
+
+    assert wrote is True
+    with open(filepath) as f:
+        assert f.read() == "new content"
+
+
+def test_overwrite_forces_rewrite_when_unchanged(tmp_path):
+    """With overwrite=True, an identical file is rewritten anyway."""
+    filepath = os.path.join(tmp_path, "wrapper.cpp")
+    with open(filepath, "w") as f:
+        f.write("content")
+
+    old_time = os.path.getmtime(filepath) - 100
+    os.utime(filepath, (old_time, old_time))
+    old_time_ns = os.stat(filepath).st_mtime_ns
+
+    wrote = write_file_if_changed(filepath, "content", overwrite=True)
+
+    assert wrote is True
+    assert os.stat(filepath).st_mtime_ns != old_time_ns