Add test suite for filecmp.py, after some discussion on bug #680494.

Right now the test cases create a files and a directory in the temp.
directory.  Raymond suggested checking files in to the test/ directory,
simplifying the setup/teardown methods; is that worth doing?

Lib/test/test_filecmp.py

@@ -0,0 +1,128 @@
+
+import os, filecmp, shutil, tempfile
+import unittest
+from test import test_support
+
+class FileCompareTestCase(unittest.TestCase):
+    def setUp(self):
+        self.name = test_support.TESTFN
+        self.name_same = test_support.TESTFN + '-same'
+        self.name_diff = test_support.TESTFN + '-diff'
+        data = 'Contents of file go here.\n'
+        for name in [self.name, self.name_same, self.name_diff]:
+            output = open(name, 'w')
+            output.write(data)
+            output.close()
+
+        output = open(self.name_diff, 'a+')
+        output.write('An extra line.\n')
+        output.close()
+        self.dir = tempfile.gettempdir()
+
+    def tearDown(self):
+        os.unlink(self.name)
+        os.unlink(self.name_same)
+        os.unlink(self.name_diff)
+
+    def test_matching(self):
+        self.failUnless(filecmp.cmp(self.name, self.name_same),
+                        "Comparing file to itself fails")
+        self.failUnless(filecmp.cmp(self.name, self.name_same, shallow=False),
+                        "Comparing file to itself fails")
+        self.failUnless(filecmp.cmp(self.name, self.name, shallow=False),
+                        "Comparing file to identical file fails")
+        self.failUnless(filecmp.cmp(self.name, self.name),
+                        "Comparing file to identical file fails")
+
+    def test_different(self):
+        self.failIf(filecmp.cmp(self.name, self.name_diff),
+                    "Mismatched files compare as equal")
+        self.failIf(filecmp.cmp(self.name, self.dir),
+                    "File and directory compare as equal")
+
+class DirCompareTestCase(unittest.TestCase):
+    def setUp(self):
+        tmpdir = tempfile.gettempdir()
+        self.dir = os.path.join(tmpdir, 'dir')
+        self.dir_same = os.path.join(tmpdir, 'dir-same')
+        self.dir_diff = os.path.join(tmpdir, 'dir-diff')
+        data = 'Contents of file go here.\n'
+        for dir in [self.dir, self.dir_same, self.dir_diff]:
+            os.mkdir(dir)
+            output = open(os.path.join(dir, 'file'), 'w')
+            output.write(data)
+            output.close()
+
+        output = open(os.path.join(self.dir_diff, 'file2'), 'w')
+        output.write('An extra file.\n')
+        output.close()
+
+    def tearDown(self):
+        shutil.rmtree(self.dir)
+        shutil.rmtree(self.dir_same)
+        shutil.rmtree(self.dir_diff)
+
+    def test_cmpfiles(self):
+        self.failUnless(filecmp.cmpfiles(self.dir, self.dir, ['file']) ==
+                        (['file'], [], []),
+                        "Comparing directory to itself fails")
+        self.failUnless(filecmp.cmpfiles(self.dir, self.dir_same, ['file']) ==
+                        (['file'], [], []),
+                        "Comparing directory to same fails")
+
+        # Try it with shallow=False
+        self.failUnless(filecmp.cmpfiles(self.dir, self.dir, ['file'],
+                                         shallow=False) ==
+                        (['file'], [], []),
+                        "Comparing directory to itself fails")
+        self.failUnless(filecmp.cmpfiles(self.dir, self.dir_same, ['file'],
+                                         shallow=False),
+                        "Comparing directory to same fails")
+
+        # Add different file2
+        output = open(os.path.join(self.dir, 'file2'), 'w')
+        output.write('Different contents.\n')
+        output.close()
+
+        self.failIf(filecmp.cmpfiles(self.dir, self.dir_same,
+                                     ['file', 'file2']) ==
+                    (['file'], ['file2'], []),
+                    "Comparing mismatched directories fails")
+
+
+    def test_dircmp(self):
+        # Check attributes for comparison of two identical directories
+        d = filecmp.dircmp(self.dir, self.dir_same)
+        self.failUnless(d.left_list == d.right_list == ['file'])
+        self.failUnless(d.common == ['file'])
+        self.failUnless(d.left_only == d.right_only == [])
+        self.failUnless(d.same_files == ['file'])
+        self.failUnless(d.diff_files == [])
+
+        # Check attributes for comparison of two different directories
+        d = filecmp.dircmp(self.dir, self.dir_diff)
+        self.failUnless(d.left_list == ['file'])
+        self.failUnless(d.right_list == ['file', 'file2'])
+        self.failUnless(d.common == ['file'])
+        self.failUnless(d.left_only == [])
+        self.failUnless(d.right_only == ['file2'])
+        self.failUnless(d.same_files == ['file'])
+        self.failUnless(d.diff_files == [])
+
+        # Add different file2
+        output = open(os.path.join(self.dir, 'file2'), 'w')
+        output.write('Different contents.\n')
+        output.close()
+        d = filecmp.dircmp(self.dir, self.dir_diff)
+        self.failUnless(d.same_files == ['file'])
+        self.failUnless(d.diff_files == ['file2'])
+
+
+def test_main():
+    suite = unittest.TestSuite()
+    for cls in FileCompareTestCase, DirCompareTestCase:
+        suite.addTest(unittest.makeSuite(cls))
+    test_support.run_suite(suite)
+
+if __name__ == "__main__":
+    test_main()