Adds tests for extract_attribute and replace_attribute

tests/test_changes.py

@@ -1,5 +1,6 @@
 from unittest2 import TestCase
-from changes.cli import increment, write_new_changelog
+from changes.cli import (extract_attribute, increment, replace_attribute,
+                         write_new_changelog)
 import os
 
 
@@ -9,6 +10,34 @@ def setUp(self):
         self.tmp_file = 'test_app/__init__.py'
         if not os.path.exists('test_app'):
             os.mkdir('test_app')
+        self.initial_init_content = [
+            '"""A test app"""',
+            '',
+            "__version__ = '0.0.1'",
+            "__url__ = 'https://github.com/michaeljoseph/testapp'",
+            "__author__ = 'Michael Joseph'",
+            "__email__ = 'michaeljoseph@gmail.com'"
+        ]
+        with open(self.tmp_file, 'w') as init_file:
+            init_file.write('\n'.join(self.initial_init_content))
+
+    def test_extract_attribute(self):
+        self.assertEquals(
+            '0.0.1',
+            extract_attribute('test_app', '__version__')
+        )
+
+    def test_replace_attribute(self):
+        replace_attribute('test_app', '__version__', '1.0.0', dry_run=False)
+
+        expected_content = list(self.initial_init_content)
+        expected_content[2] = "__version__ = '1.0.0'"
+        self.assertEquals(
+            '\n'.join(expected_content),
+            ''.join(
+                open(self.tmp_file).readlines()
+            )
+        )
 
     def test_increment(self):
         self.assertEquals(
@@ -26,7 +55,7 @@ def test_increment(self):
             increment('1.0.0', patch=True)
         )
 
-    def test_prepend_file(self):
+    def test_write_new_changelog(self):
         content = [
             'This is the heading\n\n',
             'This is the first line\n',
@@ -41,7 +70,7 @@ def test_prepend_file(self):
             ''.join(content),
             ''.join(
                 open(self.tmp_file).readlines()
-            )            
+            )
         )
 
         with open(self.tmp_file, 'w') as existing_file: