Add fit_least_squares unit test for a pure IOD orbit

adam_core/orbit_determination/__init__.py

@@ -1,3 +1,3 @@
 # flake8: noqa: F401
+from .differential_correction import OrbitDeterminationObservations, fit_least_squares
 from .fitted_orbits import FittedOrbitMembers, FittedOrbits
-from .differential_correction import fit_least_squares, OrbitDeterminationObservations

adam_core/orbit_determination/tests/test_differential_correction.py

@@ -0,0 +1,49 @@
+import os
+from importlib.resources import files
+
+import pytest
+
+from ...propagator.pyoorb import PYOORB
+from ..differential_correction import OrbitDeterminationObservations, fit_least_squares
+from ..fitted_orbits import FittedOrbitMembers, FittedOrbits
+
+
+@pytest.fixture
+def pure_iod_orbit():
+    orbit = FittedOrbits.from_parquet(
+        files("adam_core.orbit_determination.tests.data").joinpath(
+            "pure_iod_orbit.parquet"
+        )
+    )
+    orbit_members = FittedOrbitMembers.from_parquet(
+        files("adam_core.orbit_determination.tests.data").joinpath(
+            "pure_iod_orbit_members.parquet"
+        )
+    )
+    observations = OrbitDeterminationObservations.from_parquet(
+        files("adam_core.orbit_determination.tests.data").joinpath(
+            "pure_iod_orbit_observations.parquet"
+        )
+    )
+    return orbit, orbit_members, observations
+
+
+@pytest.mark.skipif(
+    os.environ.get("OORB_DATA") is None, reason="OORB_DATA environment variable not set"
+)
+def test_fit_least_squares_pure_iod_orbit(pure_iod_orbit):
+    # Test that fit_least_squares can fit and improve a pure orbit from an IOD
+    # process using least squares
+
+    orbit, orbit_members, observations = pure_iod_orbit
+    propagator = PYOORB()
+
+    fitted_orbit, fitted_orbit_members = fit_least_squares(
+        orbit, observations, propagator
+    )
+
+    assert len(fitted_orbit) == 1
+    assert len(fitted_orbit_members) == len(orbit_members) == len(observations)
+    assert fitted_orbit.reduced_chi2[0].as_py() < (orbit.reduced_chi2[0].as_py() / 1e4)
+    assert fitted_orbit.status_code[0].as_py() > 0
+    assert fitted_orbit.iterations[0].as_py() <= 50