Skip tests if external commands aren't found

Tests/helper.py

@@ -200,4 +200,29 @@ def lena(mode="RGB", cache={}):
     # cache[mode] = im
     return im
 
+
+def command_succeeds(cmd):
+    """
+    Runs the command, which must be a list of strings. Returns True if the
+    command succeeds, or False if an OSError was raised by subprocess.Popen.
+    """
+    import os
+    import subprocess
+    with open(os.devnull, 'w') as f:
+        try:
+            subprocess.Popen(cmd, stdout=f, stderr=subprocess.STDOUT).wait()
+        except OSError:
+            return False
+    return True
+
+def djpeg_available():
+    return command_succeeds(['djpeg', '--help'])
+
+def cjpeg_available():
+    return command_succeeds(['cjpeg', '--help'])
+
+def netpbm_available():
+    return command_succeeds(["ppmquant", "--help"]) and \
+           command_succeeds(["ppmtogif", "--help"])
+
 # End of file

Tests/test_file_gif.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, tearDownModule, lena
+from helper import unittest, PillowTestCase, tearDownModule, lena, netpbm_available
 
 from PIL import Image
 from PIL import GifImagePlugin
@@ -90,6 +90,7 @@ class TestFileGif(PillowTestCase):
         reloaded = roundtrip(im)[1].convert('RGB')
         self.assert_image_equal(im, reloaded)
 
+    @unittest.skipUnless(netpbm_available(), "netpbm not available")
     def test_save_netpbm_bmp_mode(self):
         img = Image.open(file).convert("RGB")
 
@@ -97,6 +98,7 @@ class TestFileGif(PillowTestCase):
         GifImagePlugin._save_netpbm(img, 0, tempfile)
         self.assert_image_similar(img, Image.open(tempfile).convert("RGB"), 0)
 
+    @unittest.skipUnless(netpbm_available(), "netpbm not available")
     def test_save_netpbm_l_mode(self):
         img = Image.open(file).convert("L")
 

Tests/test_file_jpeg.py

@@ -1,4 +1,5 @@
 from helper import unittest, PillowTestCase, tearDownModule, lena, py3
+from helper import djpeg_available, cjpeg_available
 
 import random
 from io import BytesIO
@@ -275,11 +276,13 @@ class TestFileJpeg(PillowTestCase):
                                                           1:standard_chrominance_qtable}),
                                   30)
 
+    @unittest.skipUnless(djpeg_available(), "djpeg not available")
     def test_load_djpeg(self):
         img = Image.open(test_file)
         img.load_djpeg()
         self.assert_image_similar(img, Image.open(test_file), 0)
 
+    @unittest.skipUnless(cjpeg_available(), "cjpeg not available")
     def test_save_cjpeg(self):
         img = Image.open(test_file)
 

Tests/test_shell_injection.py

@@ -1,4 +1,5 @@
 from helper import unittest, PillowTestCase, tearDownModule
+from helper import djpeg_available, cjpeg_available, netpbm_available
 
 import shutil
 
@@ -24,6 +25,7 @@ class TestShellInjection(PillowTestCase):
             # If file can't be opened, shell injection probably occurred
             Image.open(dest_file).load()
 
+    @unittest.skipUnless(djpeg_available(), "djpeg not available")
     def test_load_djpeg_filename(self):
         for filename in test_filenames:
             src_file = self.tempfile(filename)
@@ -32,14 +34,17 @@ class TestShellInjection(PillowTestCase):
             im = Image.open(src_file)
             im.load_djpeg()
 
+    @unittest.skipUnless(cjpeg_available(), "cjpeg not available")
     def test_save_cjpeg_filename(self):
         im = Image.open(test_jpg)
         self.assert_save_filename_check(im, JpegImagePlugin._save_cjpeg)
 
+    @unittest.skipUnless(netpbm_available(), "netpbm not available")
     def test_save_netpbm_filename_bmp_mode(self):
         im = Image.open(test_gif).convert("RGB")
         self.assert_save_filename_check(im, GifImagePlugin._save_netpbm)
 
+    @unittest.skipUnless(netpbm_available(), "netpbm not available")
     def test_save_netpbm_filename_l_mode(self):
         im = Image.open(test_gif).convert("L")
         self.assert_save_filename_check(im, GifImagePlugin._save_netpbm)