Compare vector results with ROOT's.

Author: jpivarski

.github/workflows/ci.yml

@@ -75,11 +75,11 @@ jobs:
   #   steps:
   #   - uses: actions/checkout@v2
 
-  #   - name: Get Conda
-  #     uses: conda-incubator/setup-miniconda@v2
-  #     with:
-  #       environment-file: environment.yml
-  #       activate-environment: vector
+    - name: Get Conda
+      uses: conda-incubator/setup-miniconda@v2
+      with:
+        environment-file: environment.yml
+        activate-environment: vector
 
   #   - name: Run tests
   #     shell: "bash -l {0}"

tests/root/test_PxPyPzEVector.py

@@ -0,0 +1,64 @@
+# Copyright (c) 2019-2021, Jonas Eschle, Jim Pivarski, Eduardo Rodrigues, and Henry Schreiner.
+#
+# Distributed under the 3-clause BSD license, see accompanying file LICENSE
+# or https://github.com/scikit-hep/vector for details.
+
+import pytest
+
+import vector
+
+# If ROOT is not available, skip these tests.
+ROOT = pytest.importorskip("ROOT")
+
+# ROOT.Math.PxPyPzEVector constructor arguments to get all the weird cases.
+constructor = [
+    (0, 0, 0, 0),
+    (0, 0, 0, 10),
+    (0, 0, 0, -10),
+    (1, 2, 3, 0),
+    (1, 2, 3, 10),
+    (1, 2, 3, -10),
+    (1, 2, 3, 2.5),
+    (1, 2, 3, -2.5),
+]
+
+# Coordinate conversion methods to apply to the VectorObject4D.
+coordinates = [
+    "to_xyzt",
+    "to_xythetat",
+    "to_xyetat",
+    "to_rhophizt",
+    "to_rhophithetat",
+    "to_rhophietat",
+    "to_xyztau",
+    "to_xythetatau",
+    "to_xyetatau",
+    "to_rhophiztau",
+    "to_rhophithetatau",
+    "to_rhophietatau",
+]
+
+
+# Run a test that compares ROOT's 'M2()' with vector's 'tau2' for all cases.
+@pytest.mark.parametrize("constructor", constructor)
+@pytest.mark.parametrize("coordinates", coordinates)
+def test_M2(constructor, coordinates):
+    assert ROOT.Math.PxPyPzEVector(*constructor).M2() == pytest.approx(
+        getattr(
+            vector.obj(**dict(zip(["x", "y", "z", "t"], constructor))), coordinates
+        )().tau2
+    )
+
+
+# Run a test that compares ROOT's 'M()' with vector's 'tau' for all cases.
+@pytest.mark.parametrize("constructor", constructor)
+@pytest.mark.parametrize("coordinates", coordinates)
+def test_M(constructor, coordinates):
+    assert ROOT.Math.PxPyPzEVector(*constructor).M() == pytest.approx(
+        getattr(
+            vector.obj(**dict(zip(["x", "y", "z", "t"], constructor))), coordinates
+        )().tau
+    )
+
+
+# etc.