Added migration script for old cassettes

tests/fixtures/migration/new_cassette.json

@@ -0,0 +1,31 @@
+[
+    {
+        "request": {
+            "body": null, 
+            "method": "GET", 
+            "headers": {
+                "Accept-Encoding": "gzip, deflate, compress", 
+                "Accept": "*/*", 
+                "User-Agent": "python-requests/2.2.1 CPython/2.6.1 Darwin/10.8.0"
+            }, 
+            "uri" : "http://httpbin.org:80/ip"
+        }, 
+        "response": {
+            "status": {
+                "message": "OK", 
+                "code": 200
+            }, 
+            "headers": [
+                "Access-Control-Allow-Origin: *\r\n", 
+                "Content-Type: application/json\r\n", 
+                "Date: Mon, 21 Apr 2014 23:13:40 GMT\r\n", 
+                "Server: gunicorn/0.17.4\r\n", 
+                "Content-Length: 32\r\n", 
+                "Connection: keep-alive\r\n"
+            ], 
+            "body": {
+                "string": "{\n  \"origin\": \"217.122.164.194\"\n}"
+            }
+        }
+    }
+]

tests/fixtures/migration/new_cassette.yaml

@@ -0,0 +1,15 @@
+- request: !!python/object:vcr.request.Request
+    body: null
+    headers: !!python/object/apply:__builtin__.frozenset
+    - - !!python/tuple [Accept-Encoding, 'gzip, deflate, compress']
+      - !!python/tuple [User-Agent, python-requests/2.2.1 CPython/2.6.1 Darwin/10.8.0]
+      - !!python/tuple [Accept, '*/*']
+    method: GET
+    uri: http://httpbin.org:80/ip
+  response:
+    body: {string: !!python/unicode "{\n  \"origin\": \"217.122.164.194\"\n}"}
+    headers: [!!python/unicode "Access-Control-Allow-Origin: *\r\n", !!python/unicode "Content-Type:
+        application/json\r\n", !!python/unicode "Date: Mon, 21 Apr 2014 23:06:09 GMT\r\n",
+      !!python/unicode "Server: gunicorn/0.17.4\r\n", !!python/unicode "Content-Length:
+        32\r\n", !!python/unicode "Connection: keep-alive\r\n"]
+    status: {code: 200, message: OK}

tests/fixtures/migration/not_cassette.txt

@@ -0,0 +1 @@
+This is not a cassette

tests/fixtures/migration/old_cassette.json

@@ -0,0 +1,34 @@
+[
+    {
+        "request": {
+            "body": null, 
+            "protocol": "http", 
+            "method": "GET", 
+            "headers": {
+                "Accept-Encoding": "gzip, deflate, compress", 
+                "Accept": "*/*", 
+                "User-Agent": "python-requests/2.2.1 CPython/2.6.1 Darwin/10.8.0"
+            }, 
+            "host": "httpbin.org", 
+            "path": "/ip", 
+            "port": 80
+        }, 
+        "response": {
+            "status": {
+                "message": "OK", 
+                "code": 200
+            }, 
+            "headers": [
+                "Access-Control-Allow-Origin: *\r\n", 
+                "Content-Type: application/json\r\n", 
+                "Date: Mon, 21 Apr 2014 23:13:40 GMT\r\n", 
+                "Server: gunicorn/0.17.4\r\n", 
+                "Content-Length: 32\r\n", 
+                "Connection: keep-alive\r\n"
+            ], 
+            "body": {
+                "string": "{\n  \"origin\": \"217.122.164.194\"\n}"
+            }
+        }
+    }
+]

tests/fixtures/migration/old_cassette.yaml

@@ -0,0 +1,18 @@
+- request: !!python/object:vcr.request.Request
+    body: null
+    headers: !!python/object/apply:__builtin__.frozenset
+    - - !!python/tuple [Accept-Encoding, 'gzip, deflate, compress']
+      - !!python/tuple [User-Agent, python-requests/2.2.1 CPython/2.6.1 Darwin/10.8.0]
+      - !!python/tuple [Accept, '*/*']
+    host: httpbin.org
+    method: GET
+    path: /ip
+    port: 80
+    protocol: http
+  response:
+    body: {string: !!python/unicode "{\n  \"origin\": \"217.122.164.194\"\n}"}
+    headers: [!!python/unicode "Access-Control-Allow-Origin: *\r\n", !!python/unicode "Content-Type:
+        application/json\r\n", !!python/unicode "Date: Mon, 21 Apr 2014 23:06:09 GMT\r\n",
+      !!python/unicode "Server: gunicorn/0.17.4\r\n", !!python/unicode "Content-Length:
+        32\r\n", !!python/unicode "Connection: keep-alive\r\n"]
+    status: {code: 200, message: OK}

tests/unit/test_migration.py

@@ -0,0 +1,36 @@
+import filecmp
+import json
+import shutil
+
+import vcr.migration
+
+
+def test_try_migrate_with_json(tmpdir):
+    cassette = tmpdir.join('cassette').strpath
+    shutil.copy('tests/fixtures/migration/old_cassette.json', cassette)
+    assert vcr.migration.try_migrate(cassette)
+    with open('tests/fixtures/migration/new_cassette.json', 'r') as f:
+        expected_json = json.load(f)
+    with open(cassette, 'r') as f:
+        actual_json = json.load(f)
+    assert actual_json == expected_json
+
+
+def test_try_migrate_with_yaml(tmpdir):
+    cassette = tmpdir.join('cassette').strpath
+    shutil.copy('tests/fixtures/migration/old_cassette.yaml', cassette)
+    assert vcr.migration.try_migrate(cassette)
+    assert filecmp.cmp(cassette, 'tests/fixtures/migration/new_cassette.yaml')
+
+
+def test_try_migrate_with_invalid_or_new_cassettes(tmpdir):
+    cassette = tmpdir.join('cassette').strpath
+    files = [
+        'tests/fixtures/migration/not_cassette.txt',
+        'tests/fixtures/migration/new_cassette.yaml',
+        'tests/fixtures/migration/new_cassette.json',
+    ]
+    for file_path in files:
+        shutil.copy(file_path, cassette)
+        assert not vcr.migration.try_migrate(cassette)
+        assert filecmp.cmp(cassette, file_path)  # shold not change file