Add test cases for abstract geometric base class

skimage/transform/tests/test_geometric.py

@@ -1,6 +1,8 @@
 import numpy as np
-from numpy.testing import assert_equal, assert_array_almost_equal
+from numpy.testing import (assert_equal, assert_array_almost_equal,
+                           assert_raises)
 from skimage.transform._geometric import _stackcopy
+from skimage.transform._geometric import GeometricTransform
 from skimage.transform import (estimate_transform,
                                SimilarityTransform, AffineTransform,
                                ProjectiveTransform, PolynomialTransform,
@@ -180,6 +182,13 @@ def test_union():
     assert tform.__class__ == ProjectiveTransform
 
 
+def test_geometric_tform():
+    tform = GeometricTransform()
+    assert_raises(NotImplementedError, tform, 0)
+    assert_raises(NotImplementedError, tform.inverse, 0)
+    assert_raises(NotImplementedError, tform.__add__, 0)
+
+
 if __name__ == "__main__":
     from numpy.testing import run_module_suite
     run_module_suite()