Simplify tests

* Make them directly executable again
* Move common stuff (md5, parameters) to helper
* Never import *
* General clean up

test/helper.py

@@ -1,22 +1,27 @@
 import errno
 import io
+import hashlib
 import json
 import os.path
 import re
 import types
 
 import youtube_dl.extractor
-from youtube_dl import YoutubeDL, YoutubeDLHandler
-from youtube_dl.utils import (
-    compat_cookiejar,
-    compat_urllib_request,
-)
+from youtube_dl import YoutubeDL
 
-youtube_dl._setup_opener(timeout=10)
 
-PARAMETERS_FILE = os.path.join(os.path.dirname(os.path.abspath(__file__)), "parameters.json")
-with io.open(PARAMETERS_FILE, encoding='utf-8') as pf:
-    parameters = json.load(pf)
+def global_setup():
+    youtube_dl._setup_opener(timeout=10)
+
+
+def get_params(override=None):
+    PARAMETERS_FILE = os.path.join(os.path.dirname(os.path.abspath(__file__)),
+                                   "parameters.json")
+    with io.open(PARAMETERS_FILE, encoding='utf-8') as pf:
+        parameters = json.load(pf)
+    if override:
+        parameters.update(override)
+    return parameters
 
 
 def try_rm(filename):
@@ -32,7 +37,7 @@ class FakeYDL(YoutubeDL):
     def __init__(self):
         # Different instances of the downloader can't share the same dictionary
         # some test set the "sublang" parameter, which would break the md5 checks.
-        params = dict(parameters)
+        params = get_params()
         super(FakeYDL, self).__init__(params)
         self.result = []
         
@@ -62,3 +67,6 @@ def get_testcases():
         for t in getattr(ie, '_TESTS', []):
             t['name'] = type(ie).__name__[:-len('IE')]
             yield t
+
+
+md5 = lambda s: hashlib.md5(s.encode('utf-8')).hexdigest()