1 files changed, 86 insertions, 0 deletions
diff --git a/config/tests/unit-mozunit.py b/config/tests/unit-mozunit.py
new file mode 100644
index 000000000..69798f4ba
--- /dev/null
+++ b/config/tests/unit-mozunit.py
@@ -0,0 +1,86 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import sys
+import os
+from mozunit import main, MockedOpen
+import unittest
+from tempfile import mkstemp
+
+class TestMozUnit(unittest.TestCase):
+    def test_mocked_open(self):
+        # Create a temporary file on the file system.
+        (fd, path) = mkstemp()
+        with os.fdopen(fd, 'w') as file:
+            file.write('foobar');
+
+        self.assertFalse(os.path.exists('file1'))
+        self.assertFalse(os.path.exists('file2'))
+
+        with MockedOpen({'file1': 'content1',
+                         'file2': 'content2'}):
+            self.assertTrue(os.path.exists('file1'))
+            self.assertTrue(os.path.exists('file2'))
+            self.assertFalse(os.path.exists('foo/file1'))
+
+            # Check the contents of the files given at MockedOpen creation.
+            self.assertEqual(open('file1', 'r').read(), 'content1')
+            self.assertEqual(open('file2', 'r').read(), 'content2')
+
+            # Check that overwriting these files alters their content.
+            with open('file1', 'w') as file:
+                file.write('foo')
+            self.assertTrue(os.path.exists('file1'))
+            self.assertEqual(open('file1', 'r').read(), 'foo')
+
+            # ... but not until the file is closed.
+            file = open('file2', 'w')
+            file.write('bar')
+            self.assertEqual(open('file2', 'r').read(), 'content2')
+            file.close()
+            self.assertEqual(open('file2', 'r').read(), 'bar')
+
+            # Check that appending to a file does append
+            with open('file1', 'a') as file:
+                file.write('bar')
+            self.assertEqual(open('file1', 'r').read(), 'foobar')
+
+            self.assertFalse(os.path.exists('file3'))
+
+            # Opening a non-existing file ought to fail.
+            self.assertRaises(IOError, open, 'file3', 'r')
+            self.assertFalse(os.path.exists('file3'))
+
+            # Check that writing a new file does create the file.
+            with open('file3', 'w') as file:
+                file.write('baz')
+            self.assertEqual(open('file3', 'r').read(), 'baz')
+            self.assertTrue(os.path.exists('file3'))
+
+            # Check the content of the file created outside MockedOpen.
+            self.assertEqual(open(path, 'r').read(), 'foobar')
+
+            # Check that overwriting a file existing on the file system
+            # does modify its content.
+            with open(path, 'w') as file:
+                file.write('bazqux')
+            self.assertEqual(open(path, 'r').read(), 'bazqux')
+
+        with MockedOpen():
+            # Check that appending to a file existing on the file system
+            # does modify its content.
+            with open(path, 'a') as file:
+                file.write('bazqux')
+            self.assertEqual(open(path, 'r').read(), 'foobarbazqux')
+
+        # Check that the file was not actually modified on the file system.
+        self.assertEqual(open(path, 'r').read(), 'foobar')
+        os.remove(path)
+
+        # Check that the file created inside MockedOpen wasn't actually
+        # created.
+        self.assertRaises(IOError, open, 'file3', 'r')
+
+if __name__ == "__main__":
+    main()