Add a simply unit test with a GH workflow

Author: tovrstra

.github/requirements-old.txt

@@ -0,0 +1,6 @@
+# Ensure changes to these dependencies are reflected in pyproject.toml
+attrs==24.2.0
+cattrs==24.1.1
+numpy==2.3.1
+scipy==1.16.0
+matplotlib==3.10.3

.github/workflows/pytest.yaml

@@ -0,0 +1,34 @@
+name: pytest
+on:
+  push:
+    branches:
+      # Run tests for change on the main branch ...
+      - main
+    tags-ignore:
+      # ... but not for tags (avoids duplicate work).
+      - '**'
+  pull_request:
+    branches:
+      # Run tests for PRs targeting the main branch.
+      - main
+
+jobs:
+  tests:
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        python-version: ["3.13", "3.14"]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install oldest versions of supported dependencies
+        if: ${{ matrix.python-version == '3.13'}}
+        run: pip install -r .github/requirements-old.txt
+      - name: Install package with test dependencies
+        run: pip install -e .[tests]
+      - name: Run pytest
+        run: pytest -vv

pyproject.toml

@@ -24,6 +24,7 @@ classifiers = [
     "Topic :: Scientific/Engineering :: Physics",
 ]
 dependencies = [
+    # Ensure changes to these dependencies are reflected in .github/requirements-old.txt
     "attrs>=24.2.0",
     "cattrs>=24.1.1",
     "numpy>=2.3.1",
@@ -32,6 +33,11 @@ dependencies = [
 ]
 dynamic = ["version"]
 
+[project.optional-dependencies]
+tests = [
+    "pytest",
+]
+
 [project.urls]
 Documentation = "https://github.com/molmod/soapboxslide/"
 Issues = "https://github.com/molmod/soapboxslide/issues"

soapboxslide.py

@@ -692,9 +692,9 @@ def to_file(self, path_npz):
         data = attrs.asdict(self)
         data["end_state"] = self.end_state.value
         data = {key: value for key, value in data.items() if value is not None}
-        np.savez_compressed(path_npz, **data, allow_pickle=False)
+        np.savez_compressed(str(path_npz), **data, allow_pickle=False)
 
     @classmethod
     def from_file(cls, path_npz):
-        data = np.load(path_npz)
+        data = np.load(str(path_npz))
         return cls(**data)

test_soapboxslide.py

@@ -0,0 +1,68 @@
+# Soap Box Slide is a computational take on soapbox racing.
+# © 2025 Toon Verstraelen
+#
+# This file is part of Soap Box Slide.
+#
+# Soap Box Slide is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 3
+# of the License, or (at your option) any later version.
+#
+# Soap Box Slide is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <http://www.gnu.org/licenses/>
+#
+# --
+"""Unit tests for Soap Box Slide."""
+
+import attrs
+import numpy as np
+
+from soapboxslide import EndState, Trajectory
+
+
+def test_npz_trajectory(tmpdir):
+    traj = Trajectory(
+        time=[0, 1, 2],
+        mass=[1, 1.2],
+        gamma=[0.3, 0.0],
+        pos=[
+            [[0, 0, 0], [1, 0, 0]],
+            [[0, 1, 0], [1, 1, 0]],
+            [[0, 2, 0], [1, 2, 0]],
+        ],
+        vel=[
+            [[0, 0, 0], [0, 0, 0]],
+            [[1, 0, 0], [1, 0, 0]],
+            [[1, 1, 0], [1, 1, 0]],
+        ],
+        grad=[
+            [[0.5, 0.1], [1.2, 0.3]],
+            [[0.6, 0.2], [1.3, 0.4]],
+            [[0.7, 0.3], [1.4, 0.5]],
+        ],
+        hess=[
+            [[0, 0, 0], [0, 0, 0]],
+            [[1, 0, 0], [1, 0, 0]],
+            [[1, 1, 0], [1, 1, 0]],
+        ],
+        spring_idx=[[0, 1]],
+        spring_par=[[100, 0.5, 1.2]],
+        end_state=EndState.STOP,
+        stop_time=30.0,
+        stop_pos=[[10, 0, 0], [10, 1, 0]],
+        stop_vel=[[0, 0, 0], [0, 0, 0]],
+    )
+    path = tmpdir.join("trajectory.npz")
+    traj.to_file(path)
+    print(path)
+    loaded_traj = Trajectory.from_file(path)
+
+    for attr in attrs.fields(Trajectory):
+        val_orig = getattr(traj, attr.name)
+        val_loaded = getattr(loaded_traj, attr.name)
+        assert np.array_equal(val_orig, val_loaded)