missing test

tests/field/test_magnetic_axis_helpers.py

@@ -0,0 +1,26 @@
+#!/usr/bin/env python3
+import unittest
+import numpy as np
+from simsopt.field.biotsavart import BiotSavart
+from simsopt.field.coil import coils_via_symmetries
+from simsopt.field.magnetic_axis_helpers import compute_on_axis_iota
+from simsopt.configs.zoo import get_ncsx_data, get_hsx_data, get_giuliani_data
+
+
+class MagneticAxisHelpers(unittest.TestCase):
+
+    def test_magnetic_axis_iota(self):
+        """
+        Verify that the rotational transform can be computed on axis
+        """
+        for (get_data, target_iota) in zip([get_hsx_data, get_ncsx_data, get_giuliani_data], [1.0418687161633922, 0.39549339846119463, 0.42297724084249616]):
+            self.subtest_magnetic_axis_iota(get_data, target_iota)
+
+    def subtest_magnetic_axis_iota(self, get_data, target_iota):
+        curves, currents, ma = get_data()
+        coils = coils_via_symmetries(curves, currents, ma.nfp, True)
+        iota = compute_on_axis_iota(ma, BiotSavart(coils))
+        np.testing.assert_allclose(iota, target_iota, rtol=1e-10, atol=1e-10)
+
+if __name__ == "__main__":
+    unittest.main()