Refactor code to import same decorator

Add `requires_img_lib` decorator and use it in test_image and test_dataio.
Update test_image to reduce redundancies.

vispy/testing/__init__.py

@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-from ._testing import (SkipTest, requires_application, requires_pyopengl,  # noqa
+from ._testing import (SkipTest, requires_application, requires_img_lib,  # noqa
                       assert_is, assert_in, assert_not_in, has_backend,  # noqa
-                      glut_skip)  # noqa
+                      glut_skip, requires_pyopengl)  # noqa
 from ._runners import _tester  # noqa

vispy/testing/_testing.py

@@ -160,3 +160,10 @@ def glut_skip():
     if app.backend_name.lower() == 'glut':
         raise SkipTest('GLUT unstable')
     return  # otherwise it's fine
+
+
+def requires_img_lib():
+    """Decorator for tests that require an image library"""
+    from ..util.dataio import _check_img_lib
+    has_img_lib = not all(c is None for c in _check_img_lib())
+    return np.testing.dec.skipif(not has_img_lib, 'imageio or PIL required')

vispy/util/tests/test_dataio.py

@@ -3,17 +3,13 @@
 from nose.tools import assert_equal, assert_raises
 from numpy.testing import assert_allclose, assert_array_equal
 
-from vispy.util.dataio import (write_mesh, read_mesh, _check_img_lib, crate,
-                               imsave, imread)
+from vispy.util.dataio import write_mesh, read_mesh, crate, imsave, imread
 from vispy.util._geom import _fast_cross_3d
 from vispy.util import _TempDir
+from vispy.testing import requires_img_lib
 
 temp_dir = _TempDir()
 
-has_img_lib = not all(c is None for c in _check_img_lib())
-requires_img_lib = np.testing.dec.skipif(not has_img_lib, 'imageio or PIL '
-                                         'required')
-
 
 def test_wavefront():
     """Test wavefront reader"""
@@ -42,7 +38,7 @@ def test_wavefront():
                     rtol=1e-10, atol=1e-10)
 
 
-@requires_img_lib
+@requires_img_lib()
 def test_read_write_image():
     """Test reading and writing of images"""
     fname = op.join(temp_dir, 'out.png')

vispy/util/tests/test_image.py

@@ -1,37 +1,33 @@
 import numpy as np
-from vispy.util import make_png
-from vispy.util.dataio import _check_img_lib, imread
 from numpy.testing import assert_array_equal
+from os import path as op
 
-has_img_lib = not all(c is None for c in _check_img_lib())
-requires_img_lib = np.testing.dec.skipif(not has_img_lib, 'imageio or PIL '
-                                         'required')
+from vispy.util import make_png, _TempDir
+from vispy.util.dataio import imread
+from vispy.testing import requires_img_lib
 
+temp_dir = _TempDir()
 
-@requires_img_lib
+
+@requires_img_lib()
 def test_make_png():
     """ Test to ensure that make_png functions correctly.
     Save random RGBA and RGB arrays onto disk as PNGs using make_png.
     Read them back with an image library and check whether the array
     saved is equal to the array read.
     """
 
-    ## RGBA
     # Create random RGBA array as type ubyte
     rgba_save = np.random.randint(256, size=(100, 100, 4)).astype(np.ubyte)
-    # Save RGBA with make_png
-    with open('rgba.png', 'wb') as f1:
-        f1.write(make_png(rgba_save))
-    # Read back and check
-    rgba_read = imread('rgba.png', 'PNG')
-    assert_array_equal(rgba_save, rgba_read)
-
-    ## RGB
     # Get rid of the alpha for RGB
     rgb_save = rgba_save[:, :, :3]
-    # Save RGB with make_png
-    with open('rgb.png', 'wb') as f2:
-        f2.write(make_png(rgb_save))
-    # Read back and check
-    rgb_read = imread('rgb.png', 'PNG')
-    assert_array_equal(rgb_save, rgb_read)
+    # Output file should be in temp
+    png_out = op.join(temp_dir, 'random.png')
+
+    for rgb_a in (rgba_save, rgb_save):
+        with open(png_out, 'wb') as f:
+            f.write(make_png(rgb_a))  # Save array with make_png
+
+        # Read back with a library and check equality
+        rgb_a_read = imread(png_out, 'PNG')
+        assert_array_equal(rgb_a, rgb_a_read)