summaryrefslogtreecommitdiffstats
path: root/python/mock-1.0.0/html/patch.html
blob: e7164d147dac485bee2c3339c1c15aecb199264d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">


<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    
    <title>Patch Decorators &mdash; Mock 1.0.0 documentation</title>
    
    <link rel="stylesheet" href="_static/nature.css" type="text/css" />
    <link rel="stylesheet" href="_static/pygments.css" type="text/css" />
    
    <script type="text/javascript">
      var DOCUMENTATION_OPTIONS = {
        URL_ROOT:    '',
        VERSION:     '1.0.0',
        COLLAPSE_INDEX: false,
        FILE_SUFFIX: '.html',
        HAS_SOURCE:  true
      };
    </script>
    <script type="text/javascript" src="_static/jquery.js"></script>
    <script type="text/javascript" src="_static/underscore.js"></script>
    <script type="text/javascript" src="_static/doctools.js"></script>
    <link rel="top" title="Mock 1.0.0 documentation" href="index.html" />
    <link rel="next" title="Helpers" href="helpers.html" />
    <link rel="prev" title="The Mock Class" href="mock.html" /> 
  </head>
  <body>
    <div class="related">
      <h3>Navigation</h3>
      <ul>
        <li class="right" style="margin-right: 10px">
          <a href="genindex.html" title="General Index"
             accesskey="I">index</a></li>
        <li class="right" >
          <a href="helpers.html" title="Helpers"
             accesskey="N">next</a> |</li>
        <li class="right" >
          <a href="mock.html" title="The Mock Class"
             accesskey="P">previous</a> |</li>
        <li><a href="index.html">Mock 1.0.0 documentation</a> &raquo;</li> 
      </ul>
    </div>  

    <div class="document">
      <div class="documentwrapper">
        <div class="bodywrapper">
          <div class="body">
            
  <div class="section" id="patch-decorators">
<h1>Patch Decorators<a class="headerlink" href="#patch-decorators" title="Permalink to this headline">¶</a></h1>
<p>The patch decorators are used for patching objects only within the scope of
the function they decorate. They automatically handle the unpatching for you,
even if exceptions are raised. All of these functions can also be used in with
statements or as class decorators.</p>
<div class="section" id="patch">
<h2>patch<a class="headerlink" href="#patch" title="Permalink to this headline">¶</a></h2>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last"><cite>patch</cite> is straightforward to use. The key is to do the patching in the
right namespace. See the section <a class="reference internal" href="#id1">where to patch</a>.</p>
</div>
<dl class="function">
<dt id="mock.patch">
<tt class="descname">patch</tt><big>(</big><em>target</em>, <em>new=DEFAULT</em>, <em>spec=None</em>, <em>create=False</em>, <em>spec_set=None</em>, <em>autospec=None</em>, <em>new_callable=None</em>, <em>**kwargs</em><big>)</big><a class="headerlink" href="#mock.patch" title="Permalink to this definition">¶</a></dt>
<dd><p><cite>patch</cite> acts as a function decorator, class decorator or a context
manager. Inside the body of the function or with statement, the <cite>target</cite>
is patched with a <cite>new</cite> object. When the function/with statement exits
the patch is undone.</p>
<p>If <cite>new</cite> is omitted, then the target is replaced with a
<a class="reference internal" href="magicmock.html#mock.MagicMock" title="mock.MagicMock"><tt class="xref py py-class docutils literal"><span class="pre">MagicMock</span></tt></a>. If <cite>patch</cite> is used as a decorator and <cite>new</cite> is
omitted, the created mock is passed in as an extra argument to the
decorated function. If <cite>patch</cite> is used as a context manager the created
mock is returned by the context manager.</p>
<p><cite>target</cite> should be a string in the form <cite>&#8216;package.module.ClassName&#8217;</cite>. The
<cite>target</cite> is imported and the specified object replaced with the <cite>new</cite>
object, so the <cite>target</cite> must be importable from the environment you are
calling <cite>patch</cite> from. The target is imported when the decorated function
is executed, not at decoration time.</p>
<p>The <cite>spec</cite> and <cite>spec_set</cite> keyword arguments are passed to the <cite>MagicMock</cite>
if patch is creating one for you.</p>
<p>In addition you can pass <cite>spec=True</cite> or <cite>spec_set=True</cite>, which causes
patch to pass in the object being mocked as the spec/spec_set object.</p>
<p><cite>new_callable</cite> allows you to specify a different class, or callable object,
that will be called to create the <cite>new</cite> object. By default <cite>MagicMock</cite> is
used.</p>
<p>A more powerful form of <cite>spec</cite> is <cite>autospec</cite>. If you set <cite>autospec=True</cite>
then the mock with be created with a spec from the object being replaced.
All attributes of the mock will also have the spec of the corresponding
attribute of the object being replaced. Methods and functions being mocked
will have their arguments checked and will raise a <cite>TypeError</cite> if they are
called with the wrong signature. For mocks
replacing a class, their return value (the &#8216;instance&#8217;) will have the same
spec as the class. See the <a class="reference internal" href="helpers.html#mock.create_autospec" title="mock.create_autospec"><tt class="xref py py-func docutils literal"><span class="pre">create_autospec()</span></tt></a> function and
<a class="reference internal" href="helpers.html#auto-speccing"><em>Autospeccing</em></a>.</p>
<p>Instead of <cite>autospec=True</cite> you can pass <cite>autospec=some_object</cite> to use an
arbitrary object as the spec instead of the one being replaced.</p>
<p>By default <cite>patch</cite> will fail to replace attributes that don&#8217;t exist. If
you pass in <cite>create=True</cite>, and the attribute doesn&#8217;t exist, patch will
create the attribute for you when the patched function is called, and
delete it again afterwards. This is useful for writing tests against
attributes that your production code creates at runtime. It is off by by
default because it can be dangerous. With it switched on you can write
passing tests against APIs that don&#8217;t actually exist!</p>
<p>Patch can be used as a <cite>TestCase</cite> class decorator. It works by
decorating each test method in the class. This reduces the boilerplate
code when your test methods share a common patchings set. <cite>patch</cite> finds
tests by looking for method names that start with <cite>patch.TEST_PREFIX</cite>.
By default this is <cite>test</cite>, which matches the way <cite>unittest</cite> finds tests.
You can specify an alternative prefix by setting <cite>patch.TEST_PREFIX</cite>.</p>
<p>Patch can be used as a context manager, with the with statement. Here the
patching applies to the indented block after the with statement. If you
use &#8220;as&#8221; then the patched object will be bound to the name after the
&#8220;as&#8221;; very useful if <cite>patch</cite> is creating a mock object for you.</p>
<p><cite>patch</cite> takes arbitrary keyword arguments. These will be passed to
the <cite>Mock</cite> (or <cite>new_callable</cite>) on construction.</p>
<p><cite>patch.dict(...)</cite>, <cite>patch.multiple(...)</cite> and <cite>patch.object(...)</cite> are
available for alternate use-cases.</p>
</dd></dl>

<p><cite>patch</cite> as function decorator, creating the mock for you and passing it into
the decorated function:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="nd">@patch</span><span class="p">(</span><span class="s">&#39;__main__.SomeClass&#39;</span><span class="p">)</span>
<span class="gp">... </span><span class="k">def</span> <span class="nf">function</span><span class="p">(</span><span class="n">normal_argument</span><span class="p">,</span> <span class="n">mock_class</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">print</span> <span class="n">mock_class</span> <span class="ow">is</span> <span class="n">SomeClass</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">function</span><span class="p">(</span><span class="bp">None</span><span class="p">)</span>
<span class="go">True</span>
</pre></div>
</div>
<p>Patching a class replaces the class with a <cite>MagicMock</cite> <em>instance</em>. If the
class is instantiated in the code under test then it will be the
<a class="reference internal" href="mock.html#mock.Mock.return_value" title="mock.Mock.return_value"><tt class="xref py py-attr docutils literal"><span class="pre">return_value</span></tt></a> of the mock that will be used.</p>
<p>If the class is instantiated multiple times you could use
<a class="reference internal" href="mock.html#mock.Mock.side_effect" title="mock.Mock.side_effect"><tt class="xref py py-attr docutils literal"><span class="pre">side_effect</span></tt></a> to return a new mock each time. Alternatively you
can set the <cite>return_value</cite> to be anything you want.</p>
<p>To configure return values on methods of <em>instances</em> on the patched class
you must do this on the <cite>return_value</cite>. For example:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">class</span> <span class="nc">Class</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">def</span> <span class="nf">method</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="gp">... </span>        <span class="k">pass</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">with</span> <span class="n">patch</span><span class="p">(</span><span class="s">&#39;__main__.Class&#39;</span><span class="p">)</span> <span class="k">as</span> <span class="n">MockClass</span><span class="p">:</span>
<span class="gp">... </span>    <span class="n">instance</span> <span class="o">=</span> <span class="n">MockClass</span><span class="o">.</span><span class="n">return_value</span>
<span class="gp">... </span>    <span class="n">instance</span><span class="o">.</span><span class="n">method</span><span class="o">.</span><span class="n">return_value</span> <span class="o">=</span> <span class="s">&#39;foo&#39;</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="n">Class</span><span class="p">()</span> <span class="ow">is</span> <span class="n">instance</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="n">Class</span><span class="p">()</span><span class="o">.</span><span class="n">method</span><span class="p">()</span> <span class="o">==</span> <span class="s">&#39;foo&#39;</span>
<span class="gp">...</span>
</pre></div>
</div>
<p>If you use <cite>spec</cite> or <cite>spec_set</cite> and <cite>patch</cite> is replacing a <em>class</em>, then the
return value of the created mock will have the same spec.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">Original</span> <span class="o">=</span> <span class="n">Class</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">patcher</span> <span class="o">=</span> <span class="n">patch</span><span class="p">(</span><span class="s">&#39;__main__.Class&#39;</span><span class="p">,</span> <span class="n">spec</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">MockClass</span> <span class="o">=</span> <span class="n">patcher</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">instance</span> <span class="o">=</span> <span class="n">MockClass</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">assert</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">instance</span><span class="p">,</span> <span class="n">Original</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">patcher</span><span class="o">.</span><span class="n">stop</span><span class="p">()</span>
</pre></div>
</div>
<p>The <cite>new_callable</cite> argument is useful where you want to use an alternative
class to the default <a class="reference internal" href="magicmock.html#mock.MagicMock" title="mock.MagicMock"><tt class="xref py py-class docutils literal"><span class="pre">MagicMock</span></tt></a> for the created mock. For example, if
you wanted a <a class="reference internal" href="mock.html#mock.NonCallableMock" title="mock.NonCallableMock"><tt class="xref py py-class docutils literal"><span class="pre">NonCallableMock</span></tt></a> to be used:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">thing</span> <span class="o">=</span> <span class="nb">object</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">with</span> <span class="n">patch</span><span class="p">(</span><span class="s">&#39;__main__.thing&#39;</span><span class="p">,</span> <span class="n">new_callable</span><span class="o">=</span><span class="n">NonCallableMock</span><span class="p">)</span> <span class="k">as</span> <span class="n">mock_thing</span><span class="p">:</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="n">thing</span> <span class="ow">is</span> <span class="n">mock_thing</span>
<span class="gp">... </span>    <span class="n">thing</span><span class="p">()</span>
<span class="gp">...</span>
<span class="gt">Traceback (most recent call last):</span>
  <span class="c">...</span>
<span class="gr">TypeError</span>: <span class="n">&#39;NonCallableMock&#39; object is not callable</span>
</pre></div>
</div>
<p>Another use case might be to replace an object with a <cite>StringIO</cite> instance:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">StringIO</span> <span class="kn">import</span> <span class="n">StringIO</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">def</span> <span class="nf">foo</span><span class="p">():</span>
<span class="gp">... </span>    <span class="k">print</span> <span class="s">&#39;Something&#39;</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nd">@patch</span><span class="p">(</span><span class="s">&#39;sys.stdout&#39;</span><span class="p">,</span> <span class="n">new_callable</span><span class="o">=</span><span class="n">StringIO</span><span class="p">)</span>
<span class="gp">... </span><span class="k">def</span> <span class="nf">test</span><span class="p">(</span><span class="n">mock_stdout</span><span class="p">):</span>
<span class="gp">... </span>    <span class="n">foo</span><span class="p">()</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="n">mock_stdout</span><span class="o">.</span><span class="n">getvalue</span><span class="p">()</span> <span class="o">==</span> <span class="s">&#39;Something</span><span class="se">\n</span><span class="s">&#39;</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">test</span><span class="p">()</span>
</pre></div>
</div>
<p>When <cite>patch</cite> is creating a mock for you, it is common that the first thing
you need to do is to configure the mock. Some of that configuration can be done
in the call to patch. Any arbitrary keywords you pass into the call will be
used to set attributes on the created mock:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">patcher</span> <span class="o">=</span> <span class="n">patch</span><span class="p">(</span><span class="s">&#39;__main__.thing&#39;</span><span class="p">,</span> <span class="n">first</span><span class="o">=</span><span class="s">&#39;one&#39;</span><span class="p">,</span> <span class="n">second</span><span class="o">=</span><span class="s">&#39;two&#39;</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">mock_thing</span> <span class="o">=</span> <span class="n">patcher</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">mock_thing</span><span class="o">.</span><span class="n">first</span>
<span class="go">&#39;one&#39;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">mock_thing</span><span class="o">.</span><span class="n">second</span>
<span class="go">&#39;two&#39;</span>
</pre></div>
</div>
<p>As well as attributes on the created mock attributes, like the
<a class="reference internal" href="mock.html#mock.Mock.return_value" title="mock.Mock.return_value"><tt class="xref py py-attr docutils literal"><span class="pre">return_value</span></tt></a> and <a class="reference internal" href="mock.html#mock.Mock.side_effect" title="mock.Mock.side_effect"><tt class="xref py py-attr docutils literal"><span class="pre">side_effect</span></tt></a>, of child mocks can
also be configured. These aren&#8217;t syntactically valid to pass in directly as
keyword arguments, but a dictionary with these as keys can still be expanded
into a <cite>patch</cite> call using <cite>**</cite>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">config</span> <span class="o">=</span> <span class="p">{</span><span class="s">&#39;method.return_value&#39;</span><span class="p">:</span> <span class="mi">3</span><span class="p">,</span> <span class="s">&#39;other.side_effect&#39;</span><span class="p">:</span> <span class="ne">KeyError</span><span class="p">}</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">patcher</span> <span class="o">=</span> <span class="n">patch</span><span class="p">(</span><span class="s">&#39;__main__.thing&#39;</span><span class="p">,</span> <span class="o">**</span><span class="n">config</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">mock_thing</span> <span class="o">=</span> <span class="n">patcher</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">mock_thing</span><span class="o">.</span><span class="n">method</span><span class="p">()</span>
<span class="go">3</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">mock_thing</span><span class="o">.</span><span class="n">other</span><span class="p">()</span>
<span class="gt">Traceback (most recent call last):</span>
  <span class="c">...</span>
<span class="gr">KeyError</span>
</pre></div>
</div>
</div>
<div class="section" id="patch-object">
<h2>patch.object<a class="headerlink" href="#patch-object" title="Permalink to this headline">¶</a></h2>
<dl class="function">
<dt id="mock.patch.object">
<tt class="descclassname">patch.</tt><tt class="descname">object</tt><big>(</big><em>target</em>, <em>attribute</em>, <em>new=DEFAULT</em>, <em>spec=None</em>, <em>create=False</em>, <em>spec_set=None</em>, <em>autospec=None</em>, <em>new_callable=None</em>, <em>**kwargs</em><big>)</big><a class="headerlink" href="#mock.patch.object" title="Permalink to this definition">¶</a></dt>
<dd><p>patch the named member (<cite>attribute</cite>) on an object (<cite>target</cite>) with a mock
object.</p>
<p><cite>patch.object</cite> can be used as a decorator, class decorator or a context
manager. Arguments <cite>new</cite>, <cite>spec</cite>, <cite>create</cite>, <cite>spec_set</cite>, <cite>autospec</cite> and
<cite>new_callable</cite> have the same meaning as for <cite>patch</cite>. Like <cite>patch</cite>,
<cite>patch.object</cite> takes arbitrary keyword arguments for configuring the mock
object it creates.</p>
<p>When used as a class decorator <cite>patch.object</cite> honours <cite>patch.TEST_PREFIX</cite>
for choosing which methods to wrap.</p>
</dd></dl>

<p>You can either call <cite>patch.object</cite> with three arguments or two arguments. The
three argument form takes the object to be patched, the attribute name and the
object to replace the attribute with.</p>
<p>When calling with the two argument form you omit the replacement object, and a
mock is created for you and passed in as an extra argument to the decorated
function:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="nd">@patch.object</span><span class="p">(</span><span class="n">SomeClass</span><span class="p">,</span> <span class="s">&#39;class_method&#39;</span><span class="p">)</span>
<span class="gp">... </span><span class="k">def</span> <span class="nf">test</span><span class="p">(</span><span class="n">mock_method</span><span class="p">):</span>
<span class="gp">... </span>    <span class="n">SomeClass</span><span class="o">.</span><span class="n">class_method</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span>
<span class="gp">... </span>    <span class="n">mock_method</span><span class="o">.</span><span class="n">assert_called_with</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">test</span><span class="p">()</span>
</pre></div>
</div>
<p><cite>spec</cite>, <cite>create</cite> and the other arguments to <cite>patch.object</cite> have the same
meaning as they do for <cite>patch</cite>.</p>
</div>
<div class="section" id="patch-dict">
<h2>patch.dict<a class="headerlink" href="#patch-dict" title="Permalink to this headline">¶</a></h2>
<dl class="function">
<dt id="mock.patch.dict">
<tt class="descclassname">patch.</tt><tt class="descname">dict</tt><big>(</big><em>in_dict</em>, <em>values=()</em>, <em>clear=False</em>, <em>**kwargs</em><big>)</big><a class="headerlink" href="#mock.patch.dict" title="Permalink to this definition">¶</a></dt>
<dd><p>Patch a dictionary, or dictionary like object, and restore the dictionary
to its original state after the test.</p>
<p><cite>in_dict</cite> can be a dictionary or a mapping like container. If it is a
mapping then it must at least support getting, setting and deleting items
plus iterating over keys.</p>
<p><cite>in_dict</cite> can also be a string specifying the name of the dictionary, which
will then be fetched by importing it.</p>
<p><cite>values</cite> can be a dictionary of values to set in the dictionary. <cite>values</cite>
can also be an iterable of <cite>(key, value)</cite> pairs.</p>
<p>If <cite>clear</cite> is True then the dictionary will be cleared before the new
values are set.</p>
<p><cite>patch.dict</cite> can also be called with arbitrary keyword arguments to set
values in the dictionary.</p>
<p><cite>patch.dict</cite> can be used as a context manager, decorator or class
decorator. When used as a class decorator <cite>patch.dict</cite> honours
<cite>patch.TEST_PREFIX</cite> for choosing which methods to wrap.</p>
</dd></dl>

<p><cite>patch.dict</cite> can be used to add members to a dictionary, or simply let a test
change a dictionary, and ensure the dictionary is restored when the test
ends.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">mock</span> <span class="kn">import</span> <span class="n">patch</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">foo</span> <span class="o">=</span> <span class="p">{}</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">with</span> <span class="n">patch</span><span class="o">.</span><span class="n">dict</span><span class="p">(</span><span class="n">foo</span><span class="p">,</span> <span class="p">{</span><span class="s">&#39;newkey&#39;</span><span class="p">:</span> <span class="s">&#39;newvalue&#39;</span><span class="p">}):</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="n">foo</span> <span class="o">==</span> <span class="p">{</span><span class="s">&#39;newkey&#39;</span><span class="p">:</span> <span class="s">&#39;newvalue&#39;</span><span class="p">}</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">assert</span> <span class="n">foo</span> <span class="o">==</span> <span class="p">{}</span>

<span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">os</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">with</span> <span class="n">patch</span><span class="o">.</span><span class="n">dict</span><span class="p">(</span><span class="s">&#39;os.environ&#39;</span><span class="p">,</span> <span class="p">{</span><span class="s">&#39;newkey&#39;</span><span class="p">:</span> <span class="s">&#39;newvalue&#39;</span><span class="p">}):</span>
<span class="gp">... </span>    <span class="k">print</span> <span class="n">os</span><span class="o">.</span><span class="n">environ</span><span class="p">[</span><span class="s">&#39;newkey&#39;</span><span class="p">]</span>
<span class="gp">...</span>
<span class="go">newvalue</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">assert</span> <span class="s">&#39;newkey&#39;</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">os</span><span class="o">.</span><span class="n">environ</span>
</pre></div>
</div>
<p>Keywords can be used in the <cite>patch.dict</cite> call to set values in the dictionary:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">mymodule</span> <span class="o">=</span> <span class="n">MagicMock</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">mymodule</span><span class="o">.</span><span class="n">function</span><span class="o">.</span><span class="n">return_value</span> <span class="o">=</span> <span class="s">&#39;fish&#39;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">with</span> <span class="n">patch</span><span class="o">.</span><span class="n">dict</span><span class="p">(</span><span class="s">&#39;sys.modules&#39;</span><span class="p">,</span> <span class="n">mymodule</span><span class="o">=</span><span class="n">mymodule</span><span class="p">):</span>
<span class="gp">... </span>    <span class="kn">import</span> <span class="nn">mymodule</span>
<span class="gp">... </span>    <span class="n">mymodule</span><span class="o">.</span><span class="n">function</span><span class="p">(</span><span class="s">&#39;some&#39;</span><span class="p">,</span> <span class="s">&#39;args&#39;</span><span class="p">)</span>
<span class="gp">...</span>
<span class="go">&#39;fish&#39;</span>
</pre></div>
</div>
<p><cite>patch.dict</cite> can be used with dictionary like objects that aren&#8217;t actually
dictionaries. At the very minimum they must support item getting, setting,
deleting and either iteration or membership test. This corresponds to the
magic methods <cite>__getitem__</cite>, <cite>__setitem__</cite>, <cite>__delitem__</cite> and either
<cite>__iter__</cite> or <cite>__contains__</cite>.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">class</span> <span class="nc">Container</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="gp">... </span>        <span class="bp">self</span><span class="o">.</span><span class="n">values</span> <span class="o">=</span> <span class="p">{}</span>
<span class="gp">... </span>    <span class="k">def</span> <span class="nf">__getitem__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">name</span><span class="p">):</span>
<span class="gp">... </span>        <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">values</span><span class="p">[</span><span class="n">name</span><span class="p">]</span>
<span class="gp">... </span>    <span class="k">def</span> <span class="nf">__setitem__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">name</span><span class="p">,</span> <span class="n">value</span><span class="p">):</span>
<span class="gp">... </span>        <span class="bp">self</span><span class="o">.</span><span class="n">values</span><span class="p">[</span><span class="n">name</span><span class="p">]</span> <span class="o">=</span> <span class="n">value</span>
<span class="gp">... </span>    <span class="k">def</span> <span class="nf">__delitem__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">name</span><span class="p">):</span>
<span class="gp">... </span>        <span class="k">del</span> <span class="bp">self</span><span class="o">.</span><span class="n">values</span><span class="p">[</span><span class="n">name</span><span class="p">]</span>
<span class="gp">... </span>    <span class="k">def</span> <span class="nf">__iter__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="gp">... </span>        <span class="k">return</span> <span class="nb">iter</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">values</span><span class="p">)</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">thing</span> <span class="o">=</span> <span class="n">Container</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">thing</span><span class="p">[</span><span class="s">&#39;one&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="mi">1</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">with</span> <span class="n">patch</span><span class="o">.</span><span class="n">dict</span><span class="p">(</span><span class="n">thing</span><span class="p">,</span> <span class="n">one</span><span class="o">=</span><span class="mi">2</span><span class="p">,</span> <span class="n">two</span><span class="o">=</span><span class="mi">3</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="n">thing</span><span class="p">[</span><span class="s">&#39;one&#39;</span><span class="p">]</span> <span class="o">==</span> <span class="mi">2</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="n">thing</span><span class="p">[</span><span class="s">&#39;two&#39;</span><span class="p">]</span> <span class="o">==</span> <span class="mi">3</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">assert</span> <span class="n">thing</span><span class="p">[</span><span class="s">&#39;one&#39;</span><span class="p">]</span> <span class="o">==</span> <span class="mi">1</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">assert</span> <span class="nb">list</span><span class="p">(</span><span class="n">thing</span><span class="p">)</span> <span class="o">==</span> <span class="p">[</span><span class="s">&#39;one&#39;</span><span class="p">]</span>
</pre></div>
</div>
</div>
<div class="section" id="patch-multiple">
<h2>patch.multiple<a class="headerlink" href="#patch-multiple" title="Permalink to this headline">¶</a></h2>
<dl class="function">
<dt id="mock.patch.multiple">
<tt class="descclassname">patch.</tt><tt class="descname">multiple</tt><big>(</big><em>target</em>, <em>spec=None</em>, <em>create=False</em>, <em>spec_set=None</em>, <em>autospec=None</em>, <em>new_callable=None</em>, <em>**kwargs</em><big>)</big><a class="headerlink" href="#mock.patch.multiple" title="Permalink to this definition">¶</a></dt>
<dd><p>Perform multiple patches in a single call. It takes the object to be
patched (either as an object or a string to fetch the object by importing)
and keyword arguments for the patches:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">with</span> <span class="n">patch</span><span class="o">.</span><span class="n">multiple</span><span class="p">(</span><span class="n">settings</span><span class="p">,</span> <span class="n">FIRST_PATCH</span><span class="o">=</span><span class="s">&#39;one&#39;</span><span class="p">,</span> <span class="n">SECOND_PATCH</span><span class="o">=</span><span class="s">&#39;two&#39;</span><span class="p">):</span>
    <span class="o">...</span>
</pre></div>
</div>
<p>Use <a class="reference internal" href="sentinel.html#mock.DEFAULT" title="mock.DEFAULT"><tt class="xref py py-data docutils literal"><span class="pre">DEFAULT</span></tt></a> as the value if you want <cite>patch.multiple</cite> to create
mocks for you. In this case the created mocks are passed into a decorated
function by keyword, and a dictionary is returned when <cite>patch.multiple</cite> is
used as a context manager.</p>
<p><cite>patch.multiple</cite> can be used as a decorator, class decorator or a context
manager. The arguments <cite>spec</cite>, <cite>spec_set</cite>, <cite>create</cite>, <cite>autospec</cite> and
<cite>new_callable</cite> have the same meaning as for <cite>patch</cite>. These arguments will
be applied to <em>all</em> patches done by <cite>patch.multiple</cite>.</p>
<p>When used as a class decorator <cite>patch.multiple</cite> honours <cite>patch.TEST_PREFIX</cite>
for choosing which methods to wrap.</p>
</dd></dl>

<p>If you want <cite>patch.multiple</cite> to create mocks for you, then you can use
<a class="reference internal" href="sentinel.html#mock.DEFAULT" title="mock.DEFAULT"><tt class="xref py py-data docutils literal"><span class="pre">DEFAULT</span></tt></a> as the value. If you use <cite>patch.multiple</cite> as a decorator
then the created mocks are passed into the decorated function by keyword.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">thing</span> <span class="o">=</span> <span class="nb">object</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">other</span> <span class="o">=</span> <span class="nb">object</span><span class="p">()</span>

<span class="gp">&gt;&gt;&gt; </span><span class="nd">@patch.multiple</span><span class="p">(</span><span class="s">&#39;__main__&#39;</span><span class="p">,</span> <span class="n">thing</span><span class="o">=</span><span class="n">DEFAULT</span><span class="p">,</span> <span class="n">other</span><span class="o">=</span><span class="n">DEFAULT</span><span class="p">)</span>
<span class="gp">... </span><span class="k">def</span> <span class="nf">test_function</span><span class="p">(</span><span class="n">thing</span><span class="p">,</span> <span class="n">other</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">thing</span><span class="p">,</span> <span class="n">MagicMock</span><span class="p">)</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">other</span><span class="p">,</span> <span class="n">MagicMock</span><span class="p">)</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">test_function</span><span class="p">()</span>
</pre></div>
</div>
<p><cite>patch.multiple</cite> can be nested with other <cite>patch</cite> decorators, but put arguments
passed by keyword <em>after</em> any of the standard arguments created by <cite>patch</cite>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="nd">@patch</span><span class="p">(</span><span class="s">&#39;sys.exit&#39;</span><span class="p">)</span>
<span class="gp">... </span><span class="nd">@patch.multiple</span><span class="p">(</span><span class="s">&#39;__main__&#39;</span><span class="p">,</span> <span class="n">thing</span><span class="o">=</span><span class="n">DEFAULT</span><span class="p">,</span> <span class="n">other</span><span class="o">=</span><span class="n">DEFAULT</span><span class="p">)</span>
<span class="gp">... </span><span class="k">def</span> <span class="nf">test_function</span><span class="p">(</span><span class="n">mock_exit</span><span class="p">,</span> <span class="n">other</span><span class="p">,</span> <span class="n">thing</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="s">&#39;other&#39;</span> <span class="ow">in</span> <span class="nb">repr</span><span class="p">(</span><span class="n">other</span><span class="p">)</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="s">&#39;thing&#39;</span> <span class="ow">in</span> <span class="nb">repr</span><span class="p">(</span><span class="n">thing</span><span class="p">)</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="s">&#39;exit&#39;</span> <span class="ow">in</span> <span class="nb">repr</span><span class="p">(</span><span class="n">mock_exit</span><span class="p">)</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">test_function</span><span class="p">()</span>
</pre></div>
</div>
<p>If <cite>patch.multiple</cite> is used as a context manager, the value returned by the
context manger is a dictionary where created mocks are keyed by name:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">with</span> <span class="n">patch</span><span class="o">.</span><span class="n">multiple</span><span class="p">(</span><span class="s">&#39;__main__&#39;</span><span class="p">,</span> <span class="n">thing</span><span class="o">=</span><span class="n">DEFAULT</span><span class="p">,</span> <span class="n">other</span><span class="o">=</span><span class="n">DEFAULT</span><span class="p">)</span> <span class="k">as</span> <span class="n">values</span><span class="p">:</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="s">&#39;other&#39;</span> <span class="ow">in</span> <span class="nb">repr</span><span class="p">(</span><span class="n">values</span><span class="p">[</span><span class="s">&#39;other&#39;</span><span class="p">])</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="s">&#39;thing&#39;</span> <span class="ow">in</span> <span class="nb">repr</span><span class="p">(</span><span class="n">values</span><span class="p">[</span><span class="s">&#39;thing&#39;</span><span class="p">])</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="n">values</span><span class="p">[</span><span class="s">&#39;thing&#39;</span><span class="p">]</span> <span class="ow">is</span> <span class="n">thing</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="n">values</span><span class="p">[</span><span class="s">&#39;other&#39;</span><span class="p">]</span> <span class="ow">is</span> <span class="n">other</span>
<span class="gp">...</span>
</pre></div>
</div>
</div>
<div class="section" id="patch-methods-start-and-stop">
<span id="start-and-stop"></span><h2>patch methods: start and stop<a class="headerlink" href="#patch-methods-start-and-stop" title="Permalink to this headline">¶</a></h2>
<p>All the patchers have <cite>start</cite> and <cite>stop</cite> methods. These make it simpler to do
patching in <cite>setUp</cite> methods or where you want to do multiple patches without
nesting decorators or with statements.</p>
<p>To use them call <cite>patch</cite>, <cite>patch.object</cite> or <cite>patch.dict</cite> as normal and keep a
reference to the returned <cite>patcher</cite> object. You can then call <cite>start</cite> to put
the patch in place and <cite>stop</cite> to undo it.</p>
<p>If you are using <cite>patch</cite> to create a mock for you then it will be returned by
the call to <cite>patcher.start</cite>.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">patcher</span> <span class="o">=</span> <span class="n">patch</span><span class="p">(</span><span class="s">&#39;package.module.ClassName&#39;</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">package</span> <span class="kn">import</span> <span class="n">module</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">original</span> <span class="o">=</span> <span class="n">module</span><span class="o">.</span><span class="n">ClassName</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">new_mock</span> <span class="o">=</span> <span class="n">patcher</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">assert</span> <span class="n">module</span><span class="o">.</span><span class="n">ClassName</span> <span class="ow">is</span> <span class="ow">not</span> <span class="n">original</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">assert</span> <span class="n">module</span><span class="o">.</span><span class="n">ClassName</span> <span class="ow">is</span> <span class="n">new_mock</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">patcher</span><span class="o">.</span><span class="n">stop</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">assert</span> <span class="n">module</span><span class="o">.</span><span class="n">ClassName</span> <span class="ow">is</span> <span class="n">original</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">assert</span> <span class="n">module</span><span class="o">.</span><span class="n">ClassName</span> <span class="ow">is</span> <span class="ow">not</span> <span class="n">new_mock</span>
</pre></div>
</div>
<p>A typical use case for this might be for doing multiple patches in the <cite>setUp</cite>
method of a <cite>TestCase</cite>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">class</span> <span class="nc">MyTest</span><span class="p">(</span><span class="n">TestCase</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">def</span> <span class="nf">setUp</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="gp">... </span>        <span class="bp">self</span><span class="o">.</span><span class="n">patcher1</span> <span class="o">=</span> <span class="n">patch</span><span class="p">(</span><span class="s">&#39;package.module.Class1&#39;</span><span class="p">)</span>
<span class="gp">... </span>        <span class="bp">self</span><span class="o">.</span><span class="n">patcher2</span> <span class="o">=</span> <span class="n">patch</span><span class="p">(</span><span class="s">&#39;package.module.Class2&#39;</span><span class="p">)</span>
<span class="gp">... </span>        <span class="bp">self</span><span class="o">.</span><span class="n">MockClass1</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">patcher1</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>
<span class="gp">... </span>        <span class="bp">self</span><span class="o">.</span><span class="n">MockClass2</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">patcher2</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>
<span class="gp">...</span>
<span class="gp">... </span>    <span class="k">def</span> <span class="nf">tearDown</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="gp">... </span>        <span class="bp">self</span><span class="o">.</span><span class="n">patcher1</span><span class="o">.</span><span class="n">stop</span><span class="p">()</span>
<span class="gp">... </span>        <span class="bp">self</span><span class="o">.</span><span class="n">patcher2</span><span class="o">.</span><span class="n">stop</span><span class="p">()</span>
<span class="gp">...</span>
<span class="gp">... </span>    <span class="k">def</span> <span class="nf">test_something</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="gp">... </span>        <span class="k">assert</span> <span class="n">package</span><span class="o">.</span><span class="n">module</span><span class="o">.</span><span class="n">Class1</span> <span class="ow">is</span> <span class="bp">self</span><span class="o">.</span><span class="n">MockClass1</span>
<span class="gp">... </span>        <span class="k">assert</span> <span class="n">package</span><span class="o">.</span><span class="n">module</span><span class="o">.</span><span class="n">Class2</span> <span class="ow">is</span> <span class="bp">self</span><span class="o">.</span><span class="n">MockClass2</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">MyTest</span><span class="p">(</span><span class="s">&#39;test_something&#39;</span><span class="p">)</span><span class="o">.</span><span class="n">run</span><span class="p">()</span>
</pre></div>
</div>
<div class="admonition caution">
<p class="first admonition-title">Caution</p>
<p>If you use this technique you must ensure that the patching is &#8220;undone&#8221; by
calling <cite>stop</cite>. This can be fiddlier than you might think, because if an
exception is raised in the setUp then tearDown is not called. <a class="reference external" href="http://pypi.python.org/pypi/unittest2">unittest2</a> cleanup functions make this
easier.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">class</span> <span class="nc">MyTest</span><span class="p">(</span><span class="n">TestCase</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">def</span> <span class="nf">setUp</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="gp">... </span>        <span class="n">patcher</span> <span class="o">=</span> <span class="n">patch</span><span class="p">(</span><span class="s">&#39;package.module.Class&#39;</span><span class="p">)</span>
<span class="gp">... </span>        <span class="bp">self</span><span class="o">.</span><span class="n">MockClass</span> <span class="o">=</span> <span class="n">patcher</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>
<span class="gp">... </span>        <span class="bp">self</span><span class="o">.</span><span class="n">addCleanup</span><span class="p">(</span><span class="n">patcher</span><span class="o">.</span><span class="n">stop</span><span class="p">)</span>
<span class="gp">...</span>
<span class="gp">... </span>    <span class="k">def</span> <span class="nf">test_something</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="gp">... </span>        <span class="k">assert</span> <span class="n">package</span><span class="o">.</span><span class="n">module</span><span class="o">.</span><span class="n">Class</span> <span class="ow">is</span> <span class="bp">self</span><span class="o">.</span><span class="n">MockClass</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">MyTest</span><span class="p">(</span><span class="s">&#39;test_something&#39;</span><span class="p">)</span><span class="o">.</span><span class="n">run</span><span class="p">()</span>
</pre></div>
</div>
<p class="last">As an added bonus you no longer need to keep a reference to the <cite>patcher</cite>
object.</p>
</div>
<p>It is also possible to stop all patches which have been started by using
<cite>patch.stopall</cite>.</p>
<dl class="function">
<dt id="mock.patch.stopall">
<tt class="descclassname">patch.</tt><tt class="descname">stopall</tt><big>(</big><big>)</big><a class="headerlink" href="#mock.patch.stopall" title="Permalink to this definition">¶</a></dt>
<dd><p>Stop all active patches. Only stops patches started with <cite>start</cite>.</p>
</dd></dl>

</div>
<div class="section" id="test-prefix">
<h2>TEST_PREFIX<a class="headerlink" href="#test-prefix" title="Permalink to this headline">¶</a></h2>
<p>All of the patchers can be used as class decorators. When used in this way
they wrap every test method on the class. The patchers recognise methods that
start with <cite>test</cite> as being test methods. This is the same way that the
<cite>unittest.TestLoader</cite> finds test methods by default.</p>
<p>It is possible that you want to use a different prefix for your tests. You can
inform the patchers of the different prefix by setting <cite>patch.TEST_PREFIX</cite>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">patch</span><span class="o">.</span><span class="n">TEST_PREFIX</span> <span class="o">=</span> <span class="s">&#39;foo&#39;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">value</span> <span class="o">=</span> <span class="mi">3</span>
<span class="go">&gt;&gt;&gt;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nd">@patch</span><span class="p">(</span><span class="s">&#39;__main__.value&#39;</span><span class="p">,</span> <span class="s">&#39;not three&#39;</span><span class="p">)</span>
<span class="gp">... </span><span class="k">class</span> <span class="nc">Thing</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">def</span> <span class="nf">foo_one</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="gp">... </span>        <span class="k">print</span> <span class="n">value</span>
<span class="gp">... </span>    <span class="k">def</span> <span class="nf">foo_two</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="gp">... </span>        <span class="k">print</span> <span class="n">value</span>
<span class="gp">...</span>
<span class="go">&gt;&gt;&gt;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">Thing</span><span class="p">()</span><span class="o">.</span><span class="n">foo_one</span><span class="p">()</span>
<span class="go">not three</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">Thing</span><span class="p">()</span><span class="o">.</span><span class="n">foo_two</span><span class="p">()</span>
<span class="go">not three</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">value</span>
<span class="go">3</span>
</pre></div>
</div>
</div>
<div class="section" id="nesting-patch-decorators">
<h2>Nesting Patch Decorators<a class="headerlink" href="#nesting-patch-decorators" title="Permalink to this headline">¶</a></h2>
<p>If you want to perform multiple patches then you can simply stack up the
decorators.</p>
<p>You can stack up multiple patch decorators using this pattern:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="nd">@patch.object</span><span class="p">(</span><span class="n">SomeClass</span><span class="p">,</span> <span class="s">&#39;class_method&#39;</span><span class="p">)</span>
<span class="gp">... </span><span class="nd">@patch.object</span><span class="p">(</span><span class="n">SomeClass</span><span class="p">,</span> <span class="s">&#39;static_method&#39;</span><span class="p">)</span>
<span class="gp">... </span><span class="k">def</span> <span class="nf">test</span><span class="p">(</span><span class="n">mock1</span><span class="p">,</span> <span class="n">mock2</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="n">SomeClass</span><span class="o">.</span><span class="n">static_method</span> <span class="ow">is</span> <span class="n">mock1</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="n">SomeClass</span><span class="o">.</span><span class="n">class_method</span> <span class="ow">is</span> <span class="n">mock2</span>
<span class="gp">... </span>    <span class="n">SomeClass</span><span class="o">.</span><span class="n">static_method</span><span class="p">(</span><span class="s">&#39;foo&#39;</span><span class="p">)</span>
<span class="gp">... </span>    <span class="n">SomeClass</span><span class="o">.</span><span class="n">class_method</span><span class="p">(</span><span class="s">&#39;bar&#39;</span><span class="p">)</span>
<span class="gp">... </span>    <span class="k">return</span> <span class="n">mock1</span><span class="p">,</span> <span class="n">mock2</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">mock1</span><span class="p">,</span> <span class="n">mock2</span> <span class="o">=</span> <span class="n">test</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">mock1</span><span class="o">.</span><span class="n">assert_called_once_with</span><span class="p">(</span><span class="s">&#39;foo&#39;</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">mock2</span><span class="o">.</span><span class="n">assert_called_once_with</span><span class="p">(</span><span class="s">&#39;bar&#39;</span><span class="p">)</span>
</pre></div>
</div>
<p>Note that the decorators are applied from the bottom upwards. This is the
standard way that Python applies decorators. The order of the created mocks
passed into your test function matches this order.</p>
<p>Like all context-managers patches can be nested using contextlib&#8217;s nested
function; <em>every</em> patching will appear in the tuple after &#8220;as&#8221;:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">contextlib</span> <span class="kn">import</span> <span class="n">nested</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">with</span> <span class="n">nested</span><span class="p">(</span>
<span class="gp">... </span>        <span class="n">patch</span><span class="p">(</span><span class="s">&#39;package.module.ClassName1&#39;</span><span class="p">),</span>
<span class="gp">... </span>        <span class="n">patch</span><span class="p">(</span><span class="s">&#39;package.module.ClassName2&#39;</span><span class="p">)</span>
<span class="gp">... </span>    <span class="p">)</span> <span class="k">as</span> <span class="p">(</span><span class="n">MockClass1</span><span class="p">,</span> <span class="n">MockClass2</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="n">package</span><span class="o">.</span><span class="n">module</span><span class="o">.</span><span class="n">ClassName1</span> <span class="ow">is</span> <span class="n">MockClass1</span>
<span class="gp">... </span>    <span class="k">assert</span> <span class="n">package</span><span class="o">.</span><span class="n">module</span><span class="o">.</span><span class="n">ClassName2</span> <span class="ow">is</span> <span class="n">MockClass2</span>
<span class="gp">...</span>
</pre></div>
</div>
</div>
<div class="section" id="where-to-patch">
<span id="id1"></span><h2>Where to patch<a class="headerlink" href="#where-to-patch" title="Permalink to this headline">¶</a></h2>
<p><cite>patch</cite> works by (temporarily) changing the object that a <em>name</em> points to with
another one. There can be many names pointing to any individual object, so
for patching to work you must ensure that you patch the name used by the system
under test.</p>
<p>The basic principle is that you patch where an object is <em>looked up</em>, which
is not necessarily the same place as where it is defined. A couple of
examples will help to clarify this.</p>
<p>Imagine we have a project that we want to test with the following structure:</p>
<div class="highlight-python"><pre>a.py
    -&gt; Defines SomeClass

b.py
    -&gt; from a import SomeClass
    -&gt; some_function instantiates SomeClass</pre>
</div>
<p>Now we want to test <cite>some_function</cite> but we want to mock out <cite>SomeClass</cite> using
<cite>patch</cite>. The problem is that when we import module b, which we will have to
do then it imports <cite>SomeClass</cite> from module a. If we use <cite>patch</cite> to mock out
<cite>a.SomeClass</cite> then it will have no effect on our test; module b already has a
reference to the <em>real</em> <cite>SomeClass</cite> and it looks like our patching had no
effect.</p>
<p>The key is to patch out <cite>SomeClass</cite> where it is used (or where it is looked up
). In this case <cite>some_function</cite> will actually look up <cite>SomeClass</cite> in module b,
where we have imported it. The patching should look like:</p>
<blockquote>
<div><cite>&#64;patch(&#8216;b.SomeClass&#8217;)</cite></div></blockquote>
<p>However, consider the alternative scenario where instead of <cite>from a import
SomeClass</cite> module b does <cite>import a</cite> and <cite>some_function</cite> uses <cite>a.SomeClass</cite>. Both
of these import forms are common. In this case the class we want to patch is
being looked up on the a module and so we have to patch <cite>a.SomeClass</cite> instead:</p>
<blockquote>
<div><cite>&#64;patch(&#8216;a.SomeClass&#8217;)</cite></div></blockquote>
</div>
<div class="section" id="patching-descriptors-and-proxy-objects">
<h2>Patching Descriptors and Proxy Objects<a class="headerlink" href="#patching-descriptors-and-proxy-objects" title="Permalink to this headline">¶</a></h2>
<p>Since version 0.6.0 both <a class="reference internal" href="#patch">patch</a> and <a class="reference internal" href="#patch-object">patch.object</a> have been able to correctly
patch and restore descriptors: class methods, static methods and properties.
You should patch these on the <em>class</em> rather than an instance.</p>
<p>Since version 0.7.0 <a class="reference internal" href="#patch">patch</a> and <a class="reference internal" href="#patch-object">patch.object</a> work correctly with some objects
that proxy attribute access, like the <a class="reference external" href="http://www.voidspace.org.uk/python/weblog/arch_d7_2010_12_04.shtml#e1198">django setttings object</a>.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">In django <cite>import settings</cite> and <cite>from django.conf import settings</cite>
return different objects. If you are using libraries / apps that do both you
may have to patch both. Grrr...</p>
</div>
</div>
</div>


          </div>
        </div>
      </div>
      <div class="sphinxsidebar">
        <div class="sphinxsidebarwrapper">
  <h3><a href="index.html">Table Of Contents</a></h3>
  <ul>
<li><a class="reference internal" href="#">Patch Decorators</a><ul>
<li><a class="reference internal" href="#patch">patch</a></li>
<li><a class="reference internal" href="#patch-object">patch.object</a></li>
<li><a class="reference internal" href="#patch-dict">patch.dict</a></li>
<li><a class="reference internal" href="#patch-multiple">patch.multiple</a></li>
<li><a class="reference internal" href="#patch-methods-start-and-stop">patch methods: start and stop</a></li>
<li><a class="reference internal" href="#test-prefix">TEST_PREFIX</a></li>
<li><a class="reference internal" href="#nesting-patch-decorators">Nesting Patch Decorators</a></li>
<li><a class="reference internal" href="#where-to-patch">Where to patch</a></li>
<li><a class="reference internal" href="#patching-descriptors-and-proxy-objects">Patching Descriptors and Proxy Objects</a></li>
</ul>
</li>
</ul>

  <h4>Previous topic</h4>
  <p class="topless"><a href="mock.html"
                        title="previous chapter">The Mock Class</a></p>
  <h4>Next topic</h4>
  <p class="topless"><a href="helpers.html"
                        title="next chapter">Helpers</a></p>
  <h3>This Page</h3>
  <ul class="this-page-menu">
    <li><a href="_sources/patch.txt"
           rel="nofollow">Show Source</a></li>
  </ul>
<div id="searchbox" style="display: none">
  <h3>Quick search</h3>
    <form class="search" action="search.html" method="get">
      <input type="text" name="q" />
      <input type="submit" value="Go" />
      <input type="hidden" name="check_keywords" value="yes" />
      <input type="hidden" name="area" value="default" />
    </form>
    <p class="searchtip" style="font-size: 90%">
    Enter search terms or a module, class or function name.
    </p>
</div>
<script type="text/javascript">$('#searchbox').show(0);</script>
        </div>
      </div>
      <div class="clearer"></div>
    </div>
    <div class="related">
      <h3>Navigation</h3>
      <ul>
        <li class="right" style="margin-right: 10px">
          <a href="genindex.html" title="General Index"
             >index</a></li>
        <li class="right" >
          <a href="helpers.html" title="Helpers"
             >next</a> |</li>
        <li class="right" >
          <a href="mock.html" title="The Mock Class"
             >previous</a> |</li>
        <li><a href="index.html">Mock 1.0.0 documentation</a> &raquo;</li> 
      </ul>
    </div>
    <div class="footer">
        &copy; Copyright 2007-2012, Michael Foord &amp; the mock team.
      Last updated on Oct 07, 2012.
      Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.1.3.
    </div>
  </body>
</html>