Create new expected_warnings helper and some cleanup

Add new helper function for expected warnings during test

Indentation cleanups and avoid skipping doctests if possible.

TODO.txt

@@ -15,7 +15,7 @@ Version 0.13
 Version 0.12
 ------------
 * Change `label` to mark background as 0, not -1, which is consistent with
-  SciPy's labelling.
+  SciPy's labelling.  Also remove doctest skip in _ccomp.pyx `label`.
 * Remove `skimage.morphology.label` from `skimage.morphology.__init__`--it now
   lives in `skimage.measure.label`.
 * Remove deprecated `reverse_map` parameter of `skimage.transform.warp`

skimage/_shared/_warnings.py

@@ -4,6 +4,7 @@ from contextlib import contextmanager
 import sys
 import warnings
 import inspect
+import re
 
 
 @contextmanager
@@ -61,3 +62,42 @@ def all_warnings():
     with warnings.catch_warnings(record=True) as w:
         warnings.simplefilter("always")
         yield w
+
+
+@contextmanager
+def expected_warnings(matching):
+    """Context for use in testing to catch known warnings matching regexes
+    
+    Parameters
+    ----------
+    matching : list of strings or compiled regexes
+        Regexes for the desired warning to catch
+
+
+    Examples
+    --------
+    >>> from skimage import data, img_as_ubyte, img_as_float
+    >>> with expected_warnings(['precision loss']):
+    ...   d = img_as_ubyte(img_as_float(data.coins()))
+
+    Notes
+    -----
+    Uses `all_warnings` to ensure all warnings are raised.
+    Upon exiting, it checks the recorded warnings for the desired matching
+    string.  Raises a warning if the match was not found or an Unexpected
+    warning is found.
+
+    """
+    with all_warnings() as w:
+        yield w
+        remaining = matching
+        for warn in w:
+            found = False
+            for match in matching:
+                if re.search(match, str(warn.message)) is not None:
+                    found = True
+                    remaining.remove(match)
+            if not found:
+                raise ValueError('Unexpected warning: %s' % str(warn.message))
+        if len(remaining) > 0:
+            raise ValueError('No warning raised matching: "%s"' % remaining[0])

skimage/measure/_ccomp.pyx

@@ -416,12 +416,12 @@ def label(input, neighbors=None, background=None, return_num=False,
      [0 1 0]
      [0 0 1]]
     >>> from skimage.measure import label
-    >>> print(label(x, neighbors=4))  # doctest: +SKIP
+    >>> print(label(x, connectivity=1)) 
     [[0 1 1]
      [2 3 1]
      [2 2 4]]
 
-    >>> print(label(x, neighbors=8))  # doctest: +SKIP
+    >>> print(label(x, connectivity=2))
     [[0 1 1]
      [1 0 1]
      [1 1 0]]

skimage/measure/_regionprops.py

@@ -473,13 +473,13 @@ def regionprops(label_image, intensity_image=None, cache=True):
     >>> from skimage import data, util
     >>> from skimage.morphology import label
     >>> img = util.img_as_ubyte(data.coins()) > 110
-    >>> label_img = label(img)  # doctest: +SKIP
+    >>> label_img = label(img, connectivity=img.ndim)
-    >>> props = regionprops(label_img)  # doctest: +SKIP
+    >>> props = regionprops(label_img)
     >>> # centroid of first labeled object
-    >>> props[0].centroid   # doctest: +SKIP 
+    >>> props[0].centroid
     (22.729879860483141, 81.912285234465827)
     >>> # centroid of first labeled object
-    >>> props[0]['centroid']  # doctest: +SKIP 
+    >>> props[0]['centroid']
     (22.729879860483141, 81.912285234465827)
 
     """

skimage/morphology/tests/test_ccomp.py

@@ -12,9 +12,9 @@ BG = -1
 
 
 def label(*args, **kwargs):
-  """Wrap the label function to avoid deprecation warning"""
+    """Wrap the label function to avoid deprecation warning"""
-  with all_warnings():
+    with all_warnings():
-    return _label(*args, **kwargs)
+        return _label(*args, **kwargs)
 
 
 class TestConnectedComponents:

skimage/novice/__init__.py

@@ -42,7 +42,7 @@ True
 451
 
 Changing `size` resizes the picture.
->>> picture.size = (45, 30)  # doctest: +SKIP
+>>> picture.size = (45, 30)
 
 You can iterate over pixels, which have RGB values between 0 and 255,
 and know their location in the picture.

skimage/segmentation/tests/test_random_walker.py

@@ -81,7 +81,7 @@ def test_2d_cg():
     assert data.shape == labels.shape
     with all_warnings():  # cg mode
         full_prob = random_walker(data, labels, beta=90, mode='cg',
-                              return_full_prob=True)
+                                  return_full_prob=True)
     assert (full_prob[1, 25:45, 40:60] >=
             full_prob[0, 25:45, 40:60]).all()
     assert data.shape == labels.shape
@@ -245,7 +245,7 @@ def test_spacing_1():
 
     # Test with `spacing` kwarg
     # First, anisotropic along Y
-    with all_warnings():  # using cd mode
+    with all_warnings():  # using cg mode
         labels_aniso = random_walker(data_aniso, labels_aniso, mode='cg',
                                      spacing=(1., 2., 1.))
     assert (labels_aniso[13:17, 26:34, 13:17] == 2).all()