Add simple test for regridding operator

test/test_operators/test_regridding.py

+# This program 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.
+#
+# This program 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/>.
+#
+# Copyright(C) 2013-2018 Max-Planck-Society
+#
+# NIFTy is being developed at the Max-Planck-Institut fuer Astrophysik
+# and financially supported by the Studienstiftung des deutschen Volkes.
+
+import unittest
+
+from numpy.testing import assert_allclose
+
+import nifty5 as ift
+
+
+class Regridding_Tests(unittest.TestCase):
+    def test_value(self):
+        s = ift.RGSpace(8)
+        Regrid = ift.RegriddingOperator(s, s.shape, 0)
+        f = ift.from_random('normal', Regrid.domain)
+        assert_allclose(f.to_global_data(), Regrid(f).to_global_data())