Improve pytest configuration to allow specific tests as CLI args

The previous test configuration made it difficult to run a single test
with the pytest CLI. There were two major issues:

- The Tests directory was not a package. It now includes a __init__.py
  file and imports from other tests modules are done with relative
  imports.

- setup.cfg always specified the Tests directory. So even if a specific
  test were specified as a CLI arg, this configuration would also always
  include all tests. This configuration has been removed to allow
  specifying a single test on the command line.

Contributors can now run specific tests with a single command such as:

  $ tox -e py37 -- Tests/test_file_pdf.py::TestFilePdf.test_rgb

This makes it easy and faster to iterate on a single test failure and is
very familiar to those that have previously used tox and pytest.

When running tox or pytest with no arguments, they still discover and
runs all tests in the Tests directory.

Tests/bench_cffi_access.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 # Not running this test by default. No DOS against Travis CI.
 

Tests/bench_get.py

@@ -1,4 +1,4 @@
-import helper
+from . import helper
 import timeit
 
 import sys

Tests/check_fli_overflow.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 from PIL import Image
 
 TEST_FILE = "Tests/images/fli_overflow.fli"

Tests/check_imaging_leaks.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python
 
 from __future__ import division
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 import sys
 from PIL import Image
 

Tests/check_j2k_leaks.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 import sys
 from PIL import Image
 from io import BytesIO

Tests/check_j2k_overflow.py

@@ -1,5 +1,5 @@
 from PIL import Image
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 
 class TestJ2kEncodeOverflow(PillowTestCase):

Tests/check_jpeg_leaks.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 from io import BytesIO
 import sys
 

Tests/check_large_memory.py

@@ -1,6 +1,6 @@
 import sys
 
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 # This test is not run automatically.
 #

Tests/check_large_memory_numpy.py

@@ -1,6 +1,6 @@
 import sys
 
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 # This test is not run automatically.
 #

Tests/check_libtiff_segfault.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 from PIL import Image
 
 TEST_FILE = "Tests/images/libtiff_segfault.tif"

Tests/check_png_dos.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 from PIL import Image, PngImagePlugin, ImageFile
 from io import BytesIO
 import zlib

Tests/test_000_sanity.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 import PIL
 import PIL.Image

Tests/test_binary.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import _binary
 

Tests/test_bmp_reference.py

@@ -1,5 +1,5 @@
 from __future__ import print_function
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import Image
 import os

Tests/test_box_blur.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import Image, ImageFilter
 

Tests/test_color_lut.py

@@ -3,7 +3,7 @@
 from array import array
 
 from PIL import Image, ImageFilter
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 try:
     import numpy

Tests/test_core_resources.py

@@ -2,7 +2,7 @@
 
 import sys
 
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 from PIL import Image
 
 

Tests/test_decompression_bomb.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import Image
 

Tests/test_features.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import features
 

Tests/test_file_blp.py

@@ -1,6 +1,6 @@
 from PIL import Image
 
-from helper import PillowTestCase, unittest
+from .helper import PillowTestCase, unittest
 
 
 class TestFileBlp(PillowTestCase):

Tests/test_file_bmp.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import Image, BmpImagePlugin
 import io

Tests/test_file_bufrstub.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import BufrStubImagePlugin, Image
 

Tests/test_file_container.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import Image
 from PIL import ContainerIO

Tests/test_file_cur.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import Image, CurImagePlugin
 

Tests/test_file_dcx.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import Image, DcxImagePlugin
 

Tests/test_file_dds.py

@@ -1,6 +1,6 @@
 from io import BytesIO
 
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 from PIL import Image, DdsImagePlugin
 
 TEST_FILE_DXT1 = "Tests/images/dxt1-rgb-4bbp-noalpha_MipMaps-1.dds"

Tests/test_file_eps.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import Image, EpsImagePlugin
 import io

Tests/test_file_fitsstub.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import FitsStubImagePlugin, Image
 

Tests/test_file_fli.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import Image, FliImagePlugin
 

Tests/test_file_fpx.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 try:
     from PIL import FpxImagePlugin

Tests/test_file_ftex.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 from PIL import Image
 
 

Tests/test_file_gbr.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import Image, GbrImagePlugin
 

Tests/test_file_gd.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import GdImageFile
 

Tests/test_file_gif.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper, netpbm_available
+from .helper import unittest, PillowTestCase, hopper, netpbm_available
 
 from PIL import Image, ImagePalette, GifImagePlugin
 

Tests/test_file_gimpgradient.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import GimpGradientFile
 

Tests/test_file_gimppalette.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL.GimpPaletteFile import GimpPaletteFile
 

Tests/test_file_gribstub.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import GribStubImagePlugin, Image
 

Tests/test_file_hdf5stub.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import Hdf5StubImagePlugin, Image
 

Tests/test_file_icns.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import Image, IcnsImagePlugin
 

Tests/test_file_ico.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 import io
 from PIL import Image, IcoImagePlugin

Tests/test_file_im.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import Image, ImImagePlugin
 

Tests/test_file_iptc.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import Image, IptcImagePlugin
 

Tests/test_file_jpeg.py

@@ -1,5 +1,5 @@
-from helper import unittest, PillowTestCase, hopper
-from helper import djpeg_available, cjpeg_available
+from .helper import unittest, PillowTestCase, hopper
+from .helper import djpeg_available, cjpeg_available
 
 from io import BytesIO
 import os

Tests/test_file_jpeg2k.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import Image, Jpeg2KImagePlugin
 from io import BytesIO

Tests/test_file_libtiff.py

@@ -1,5 +1,5 @@
 from __future__ import print_function
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 from PIL import features
 from PIL._util import py3
 

Tests/test_file_libtiff_small.py

@@ -1,8 +1,8 @@
-from helper import unittest
+from .helper import unittest
 
 from PIL import Image
 
-from test_file_libtiff import LibTiffTestCase
+from .test_file_libtiff import LibTiffTestCase
 
 
 class TestFileLibTiffSmall(LibTiffTestCase):

Tests/test_file_mcidas.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import Image, McIdasImagePlugin
 

Tests/test_file_mic.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import Image, ImagePalette, features
 

Tests/test_file_mpo.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 from io import BytesIO
 from PIL import Image
 

Tests/test_file_msp.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import Image, MspImagePlugin
 

Tests/test_file_palm.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper, imagemagick_available
+from .helper import unittest, PillowTestCase, hopper, imagemagick_available
 
 import os.path
 

Tests/test_file_pcd.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 from PIL import Image
 
 

Tests/test_file_pcx.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import Image, ImageFile, PcxImagePlugin
 

Tests/test_file_pdf.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 from PIL import Image, PdfParser
 import io
 import os

Tests/test_file_pixar.py

@@ -1,4 +1,4 @@
-from helper import hopper, unittest, PillowTestCase
+from .helper import hopper, unittest, PillowTestCase
 
 from PIL import Image, PixarImagePlugin
 

Tests/test_file_png.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, PillowLeakTestCase, hopper
+from .helper import unittest, PillowTestCase, PillowLeakTestCase, hopper
 from PIL import Image, ImageFile, PngImagePlugin
 from PIL._util import py3
 

Tests/test_file_ppm.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import Image
 

Tests/test_file_psd.py

@@ -1,4 +1,4 @@
-from helper import hopper, unittest, PillowTestCase
+from .helper import hopper, unittest, PillowTestCase
 
 from PIL import Image, PsdImagePlugin
 

Tests/test_file_sgi.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import Image, SgiImagePlugin
 

Tests/test_file_spider.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import Image
 from PIL import ImageSequence

Tests/test_file_sun.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase, hopper
+from .helper import unittest, PillowTestCase, hopper
 
 from PIL import Image, SunImagePlugin
 

Tests/test_file_tar.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from .helper import unittest, PillowTestCase
 
 from PIL import Image, TarIO