1 files changed, 87 insertions, 0 deletions
diff --git a/config/tests/unit-mozunit.py b/config/tests/unit-mozunit.py
new file mode 100644
index 0000000000..0c18ec7227
--- /dev/null
+++ b/config/tests/unit-mozunit.py
@@ -0,0 +1,87 @@
+# 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/.
+
+from __future__ import absolute_import
+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()