diff --git a/skimage/_shared/_interpolation_test.pyx b/skimage/_shared/_interpolation_test.pyx
new file mode 100644
index 00000000..1c243926
--- /dev/null
+++ b/skimage/_shared/_interpolation_test.pyx
@@ -0,0 +1,5 @@
+from interpolation cimport coord_map as _coord_map
+
+def coord_map(Py_ssize_t dim, long coord, mode):
+    cdef char mode_c = ord(mode[0].upper())
+    return _coord_map(dim, coord, mode_c)
\ No newline at end of file
diff --git a/skimage/_shared/setup.py b/skimage/_shared/setup.py
index 4c36b97e..6a6baeda 100644
--- a/skimage/_shared/setup.py
+++ b/skimage/_shared/setup.py
@@ -15,11 +15,12 @@ def configuration(parent_package='', top_path=None):
 
     cython(['geometry.pyx'], working_path=base_path)
     cython(['transform.pyx'], working_path=base_path)
+    cython(['_interpolation_test.pyx'], working_path=base_path)
 
     config.add_extension('geometry', sources=['geometry.c'])
     config.add_extension('transform', sources=['transform.c'],
                          include_dirs=[get_numpy_include_dirs()])
-
+    config.add_extension('_interpolation_test', sources=['_interpolation_test.c'])
     return config
 
 
diff --git a/skimage/_shared/tests/test_interpolation.py b/skimage/_shared/tests/test_interpolation.py
new file mode 100644
index 00000000..98bafb5b
--- /dev/null
+++ b/skimage/_shared/tests/test_interpolation.py
@@ -0,0 +1,19 @@
+from skimage._shared._interpolation_test import coord_map
+from numpy.testing import assert_array_equal
+
+def test_coord_map():
+
+    reflect = [coord_map(4, n, 'R') for n in range(-6, 6)]
+    expected_reflect = [2, 3, 3, 2, 1, 0, 0, 1, 2, 3, 3, 2]
+    assert_array_equal(reflect, expected_reflect)
+
+    wrap = [coord_map(4, n, 'W') for n in range(-6, 6)]
+    expected_wrap = [2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1]
+    assert_array_equal(wrap, expected_wrap)
+
+    nearest = [coord_map(4, n, 'N') for n in range(-6, 6)]
+    expected_neareset = [0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 3, 3]
+    assert_array_equal(nearest, expected_neareset)
+
+    other = [coord_map(4, n, 'undefined') for n in range(-6, 6)]
+    assert_array_equal(other, list(range(-6, 6)))
\ No newline at end of file