Don't save cassette when it hasn't been modified

tests/integration/test_disksaver.py

@@ -0,0 +1,43 @@
+'''Basic tests about save behavior'''
+# coding=utf-8
+
+# External imports
+import os
+import urllib2
+
+# Internal imports
+import vcr
+
+def test_disk_saver_nowrite(tmpdir):
+    '''Ensure that when you close a cassette without changing it it doesn't rewrite the file'''
+    fname = str(tmpdir.join('synopsis.yaml'))
+    with vcr.use_cassette(fname) as cass:
+        urllib2.urlopen('http://www.iana.org/domains/reserved').read()
+        assert cass.play_count == 0
+    last_mod = os.path.getmtime(fname)
+
+    with vcr.use_cassette(fname) as cass:
+        urllib2.urlopen('http://www.iana.org/domains/reserved').read()
+        assert cass.play_count == 1
+        assert cass.dirty == False
+    last_mod2 = os.path.getmtime(fname)
+
+    assert last_mod == last_mod2
+
+def test_disk_saver_write(tmpdir):
+    '''Ensure that when you close a cassette with changing it it does rewrite the file'''
+    fname = str(tmpdir.join('synopsis.yaml'))
+    with vcr.use_cassette(fname) as cass:
+        urllib2.urlopen('http://www.iana.org/domains/reserved').read()
+        assert cass.play_count == 0
+    last_mod = os.path.getmtime(fname)
+
+    with vcr.use_cassette(fname) as cass:
+        urllib2.urlopen('http://www.iana.org/domains/reserved').read()
+        urllib2.urlopen('http://httpbin.org/').read()
+        assert cass.play_count == 1
+        assert cass.dirty
+    last_mod2 = os.path.getmtime(fname)
+
+    assert last_mod != last_mod2
+