fix(observers): Correct Offset namedtuple name. (#3)

If we lie about the the name of the namedtuple, it isn't pickleable.

Also, the start of a test-suite

.github/workflows/test.yaml

@@ -0,0 +1,30 @@
+name: ch_ephem-tests
+on:
+  pull_request:
+    branches:
+    - master
+  push:
+    branches:
+    - master
+
+jobs:
+  run-tests:
+
+    strategy:
+      matrix:
+        python-version: ["3.9", "3.12"]
+
+    runs-on: ubuntu-latest
+    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 pip dependencies
+      run: pip install -e .[test]
+
+    - name: Run tests
+      run: pytest -v .

ch_ephem/observers.py

@@ -58,7 +58,7 @@
 _observers = None
 
 # tangent-space offset representation.
-_offset = namedtuple("Offset", ["x", "y", "z"])
+Offset = namedtuple("Offset", ["x", "y", "z"])
 
 
 class Observer(CaputObserver):
@@ -94,7 +94,7 @@ def __init__(
         super().__init__(lon, lat, alt, lsd_start, sf_wrapper)
         self.rotation = rot
         self.roll = roll
-        self.offset = _offset(*offset)
+        self.offset = Offset(*offset)
 
 
 def all() -> dict[str, Observer]:

tests/test_observers.py

@@ -0,0 +1,31 @@
+"""Test ch_ephem.observers"""
+
+import pickle
+
+from ch_ephem import observers
+
+
+def test_pickle_observers():
+    """Observers should be picklable."""
+
+    # These are all small powers of two to
+    # avoid floating-point shennanigans
+    test = observers.Observer(lat=1, lon=2, alt=4, rot=8, roll=16, offset=(32, 64, 128))
+
+    pickled = pickle.dumps(test)
+    assert pickled is not None
+
+    result = pickle.loads(pickled)
+
+    assert result.latitude == 1
+    assert result.longitude == 2
+    assert result.altitude == 4
+    assert result.rotation == 8
+    assert result.roll == 16
+    assert result.offset.x == 32
+    assert result.offset.y == 64
+    assert result.offset.z == 128
+
+    repickled = pickle.dumps(result)
+
+    assert pickled == repickled