Full test coverage for structural similarity

skimage/measure/tests/test_structural_similarity.py

@@ -1,5 +1,5 @@
 import numpy as np
-from numpy.testing import assert_equal
+from numpy.testing import assert_equal, assert_raises
 
 from skimage.measure import structural_similarity as ssim
 
@@ -24,20 +24,18 @@ def test_ssim_image():
     S1 = ssim(X, Y, win_size=3)
     assert(S1 < 0.3)
 
-## Come up with a better way of testing the gradient
-##
-## def test_ssim_grad():
-##     N = 30
-##     X = np.random.random((N, N)) * 255
-##     Y = np.random.random((N, N)) * 255
 
-##     def func(Y):
-##         return ssim(X, Y, dynamic_range=255)
+def test_ssim_grad():
+    N = 30
+    X = np.random.random((N, N)) * 255
+    Y = np.random.random((N, N)) * 255
 
-##     def grad(Y):
-##         return ssim(X, Y, dynamic_range=255, gradient=True)[1]
+    f = ssim(X, Y, dynamic_range=255)
+    g = ssim(X, Y, dynamic_range=255, gradient=True)
 
-##     assert(np.all(opt.check_grad(func, grad, Y) < 0.05))
+    assert f < 0.05
+    assert g[0] < 0.05
+    assert np.all(g[1] < 0.05)
 
 
 def test_ssim_dtype():
@@ -56,5 +54,15 @@ def test_ssim_dtype():
     assert S2 < 0.1
 
 
+def test_invalid_input():
+    X = np.zeros((3, 3), dtype=np.double)
+    Y = np.zeros((3, 3), dtype=np.int)
+    assert_raises(ValueError, ssim, X, Y)
+
+    Y = np.zeros((4, 4), dtype=np.double)
+    assert_raises(ValueError, ssim, X, Y)
+
+    assert_raises(ValueError, ssim, X, X, win_size=8)
+
 if __name__ == "__main__":
     np.testing.run_module_suite()