Add some Windows-only tests

Tests/test_imagewin.py

@@ -1,6 +1,7 @@
-from helper import unittest, PillowTestCase
+from helper import unittest, PillowTestCase, hopper
 
 from PIL import ImageWin
+import sys
 
 
 class TestImageWin(PillowTestCase):
@@ -32,6 +33,92 @@ class TestImageWin(PillowTestCase):
         self.assertEqual(wnd2, 50)
 
 
+@unittest.skipUnless(sys.platform.startswith('win32'), "Windows only")
+class TestImageWinDib(PillowTestCase):
+
+    def test_dib_image(self):
+        # Arrange
+        im = hopper()
+
+        # Act
+        dib = ImageWin.Dib(im)
+
+        # Assert
+        self.assertEqual(dib.size, im.size)
+
+    def test_dib_mode_string(self):
+        # Arrange
+        mode = "RGBA"
+        size = (128, 128)
+
+        # Act
+        dib = ImageWin.Dib(mode, size)
+
+        # Assert
+        self.assertEqual(dib.size, (128, 128))
+
+    def test_dib_paste(self):
+        # Arrange
+        im = hopper()
+
+        mode = "RGBA"
+        size = (128, 128)
+        dib = ImageWin.Dib(mode, size)
+
+        # Act
+        dib.paste(im)
+
+        # Assert
+        self.assertEqual(dib.size, (128, 128))
+
+    def test_dib_paste_bbox(self):
+        # Arrange
+        im = hopper()
+        bbox = (0, 0, 10, 10)
+
+        mode = "RGBA"
+        size = (128, 128)
+        dib = ImageWin.Dib(mode, size)
+
+        # Act
+        dib.paste(im, bbox)
+
+        # Assert
+        self.assertEqual(dib.size, (128, 128))
+
+    def test_dib_frombytes_tobytes_roundtrip(self):
+        # Arrange
+        # Make two different DIB images
+        im = hopper()
+        dib1 = ImageWin.Dib(im)
+
+        mode = "RGB"
+        size = (128, 128)
+        dib2 = ImageWin.Dib(mode, size)
+
+        # Confirm they're different
+        self.assertNotEqual(dib1.tobytes(), dib2.tobytes())
+
+        # Act
+        # Make one the same as the using tobytes()/frombytes()
+        buffer = dib1.tobytes()
+        dib2.frombytes(buffer)
+
+        # Assert
+        # Confirm they're the same
+        self.assertEqual(dib1.tobytes(), dib2.tobytes())
+
+    def test_dib_fromstring_tostring_deprecated(self):
+        # Arrange
+        im = hopper()
+        dib = ImageWin.Dib(im)
+        buffer = dib.tobytes()
+
+        # Act/Assert
+        self.assert_warning(DeprecationWarning, lambda: dib.tostring())
+        self.assert_warning(DeprecationWarning, lambda: dib.fromstring(buffer))
+
+
 if __name__ == '__main__':
     unittest.main()