1
<?xml version="1.0" encoding="UTF-8" ?>
2
<!DOCTYPE chapter SYSTEM "chapter.dtd">
7
<year>2011</year><year>2011</year>
8
<holder>Ericsson AB. All Rights Reserved.</holder>
11
The contents of this file are subject to the Erlang Public License,
12
Version 1.1, (the "License"); you may not use this file except in
13
compliance with the License. You should have received a copy of the
14
Erlang Public License along with this software. If not, it can be
15
retrieved online at http://www.erlang.org/.
17
Software distributed under the License is distributed on an "AS IS"
18
basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
19
the License for the specific language governing rights and limitations
24
<title>Common Test Hooks</title>
25
<prepared>Lukas Larsson</prepared>
29
<file>ct_hooks_chapter.xml</file>
32
<marker id="general"></marker>
34
<title>General</title>
35
<warning><p>This feature is in alpha release right now. This means that the
36
interface may change in the future and that there may be bugs. We
37
encourage you to use this feature, but be prepared
38
that there might be bugs and that the interface might change
39
inbetween releases.</p></warning>
41
The <em>Common Test Hook</em> (henceforth called CTH) framework allows
42
extensions of the default behaviour of Common Test by means of hooks
43
before and after all test suite calls. CTHs allow advanced Common Test
44
users to abstract out behaviour which is common to multiple test suites
45
without littering all test suites with library calls. Some example
46
usages are: logging, starting and monitoring external systems,
47
building C files needed by the tests and much more!</p>
49
<p>In brief, Common Test Hooks allows you to:</p>
52
<item>Manipulate the runtime config before each suite
53
configuration call</item>
54
<item>Manipulate the return of all suite configuration calls and in
55
extension the result of the test themselves.</item>
58
<p>The following sections describe how to use CTHs, when they are run
59
and how to manipulate your test results in a CTH</p>
61
<warning><p>When executing within a CTH all timetraps are shutoff. So
62
if your CTH never returns, the entire test run will be stalled!</p>
67
<marker id="installing"></marker>
69
<title>Installing a CTH</title>
70
<p>There are multiple ways to install a CTH in your test run. You can do it
71
for all tests in a run, for specific test suites and for specific groups
72
within a test suite. If you want a CTH to be present in all test suites
73
within your test run there are three different ways to accomplish that.
77
<item>Add <c>-ct_hooks</c> as an argument to
78
<seealso marker="run_test_chapter#ct_run">ct_run</seealso>.
79
To add multiple CTHs using this method append them to each other
80
using the keyword <c>and</c>, i.e.
81
<c>ct_run -ct_hooks cth1 [{debug,true}] and cth2 ...</c>.</item>
82
<item>Add the <c>ct_hooks</c> tag to your
83
<seealso marker="run_test_chapter#test_specifications">
84
Test Specification</seealso></item>
85
<item>Add the <c>ct_hooks</c> tag to your call to
86
<seealso marker="ct#run_test-1">ct:run_test/1</seealso></item>
89
<p>You can also add CTHs within a test suite. This is done by returning
90
<c>{ct_hooks,[CTH]}</c> in the config list from
91
<seealso marker="common_test#Module:suite-0">suite/0</seealso>,
92
<seealso marker="common_test#Module:init_per_suite-1">
93
init_per_suite/1</seealso> or
94
<seealso marker="common_test#Module:init_per_group-2">
95
init_per_group/2</seealso>. <c>CTH</c> in this case can be either
96
only the module name of the CTH or a tuple with the module name and the
97
initial arguments to the CTH. Eg:
98
<c>{ct_hooks,[my_cth_module]}</c> or
99
<c>{ct_hooks,[{my_cth_module,[{debug,true}]}]}</c></p>
102
<title>Overriding CTHs</title>
103
<p>By default each installation of a CTH will cause a new instance of it
104
to be activated. This can cause problems if you want to be able to
105
override CTHs in test specifications while still having them in the
106
suite info function. The
107
<seealso marker="ct_hooks#Module:id-1">id/1</seealso>
108
callback exists to address this problem. By returning the same
109
<c>id</c> in both places, Common Test knows that this CTH
110
has already been installed and will not try to install it again.</p>
117
<title>CTH Scope</title>
118
<p>Once the CTH is installed into a certain test run it will be there until
119
its scope is expired. The scope of a CTH depends on when it is
121
The <seealso marker="ct_hooks#Module:init-2">init/2</seealso> is
122
called at the beginning of the scope and the
123
<seealso marker="ct_hooks#Module:terminate-1">terminate/1
124
</seealso> function is called when the scope ends.</p>
127
<cell><em>CTH Installed in</em></cell>
128
<cell><em>CTH scope begins before</em></cell>
129
<cell><em>CTH scope ends after</em></cell>
132
<cell><seealso marker="run_test_chapter#ct_run">ct_run</seealso></cell>
133
<cell>the first test suite is to be run.</cell>
134
<cell>the last test suite has been run.</cell>
137
<cell><seealso marker="ct#run_test-1">ct:run_test</seealso></cell>
138
<cell>the first test suite is to be run.</cell>
139
<cell>the last test suite has been run.</cell>
142
<cell><seealso marker="run_test_chapter#test_specifications">
143
Test Specification</seealso></cell>
144
<cell>the first test suite is to be run.</cell>
145
<cell>the last test suite has been run.</cell>
148
<cell><seealso marker="common_test#Module:suite-0">suite/0
150
<cell><seealso marker="ct_hooks#Module:pre_init_per_suite-3">
151
pre_init_per_suite/3</seealso> is called.</cell>
152
<cell><seealso marker="ct_hooks#Module:post_end_per_suite-4">
153
post_end_per_suite/4</seealso> has been called for that test suite.</cell>
156
<cell><seealso marker="common_test#Module:init_per_suite-1">
157
init_per_suite/1</seealso></cell>
158
<cell><seealso marker="ct_hooks#Module:post_init_per_suite-4">
159
post_init_per_suite/4</seealso> is called.</cell>
160
<cell><seealso marker="ct_hooks#Module:post_end_per_suite-4">
161
post_end_per_suite/4</seealso> has been called for that test suite.</cell>
164
<cell><seealso marker="common_test#Module:init_per_group-2">
165
init_per_group/2</seealso></cell>
166
<cell><seealso marker="ct_hooks#Module:post_init_per_group-4">
167
post_init_per_group/4</seealso> is called.</cell>
168
<cell><seealso marker="ct_hooks#Module:post_end_per_suite-4">
169
post_end_per_group/4</seealso> has been called for that group.</cell>
171
<tcaption>Scope of a CTH</tcaption>
175
<title>CTH Processes and Tables</title>
176
<p>CTHs are run with the same process scoping as normal test suites
177
i.e. a different process will execute the init_per_suite hooks then the
178
init_per_group or per_testcase hooks. So if you want to spawn a
179
process in the CTH you cannot link with the CTH process as it will exit
180
after the post hook ends. Also if you for some reason need an ETS
181
table with your CTH, you will have to spawn a process which handles
187
<marker id="manipulating"/>
189
<title>Manipulating tests</title>
190
<p>It is through CTHs possible to manipulate the results of tests and
191
configuration functions. The main purpose of doing this with CTHs is to
192
allow common patterns to be abstracted out from test test suites and applied to
193
multiple test suites without duplicating any code. All of the callback
194
functions for a CTH follow a common interface, this interface is
197
<p>It is only possible to hook into test function which exists in the test
198
suite. So in order for a CTH to hook in before
199
<seealso marker="common_test#Module:init_per_suite-1">init_per_suite</seealso>,
200
the <seealso marker="common_test#Module:init_per_suite-1">init_per_suite</seealso>
201
function must exist in the test suite.</p>
205
<title>Pre Hooks</title>
207
It is possible in a CTH to hook in behaviour before
208
<seealso marker="common_test#Module:init_per_suite-1">init_per_suite</seealso>,
209
<seealso marker="common_test#Module:init_per_suite-1">init_per_group</seealso>,
210
<seealso marker="common_test#Module:init_per_suite-1">init_per_testcase</seealso>,
211
<seealso marker="common_test#Module:init_per_suite-1">end_per_group</seealso> and
212
<seealso marker="common_test#Module:init_per_suite-1">end_per_suite</seealso>.
213
This is done in the CTH functions called pre_<name of function>.
214
All of these functions take the same three arguments: <c>Name</c>,
215
<c>Config</c> and <c>CTHState</c>. The return value of the CTH function
216
is always a combination of an result for the suite/group/test and an
217
updated <c>CTHState</c>. If you want the test suite to continue on
218
executing you should return the config list which you want the test to
219
use as the result. If you for some reason want to skip/fail the test,
220
return a tuple with <c>skip</c> or <c>fail</c> and a reason as the
223
<code>pre_init_per_suite(SuiteName, Config, CTHState) ->
225
{error,_Reason} ->
226
{{fail, "Could not connect to DB"}, CTHState};
228
{[{db_handle, Handle} | Config], CTHState#state{ handle = Handle }}
235
<title>Post Hooks</title>
236
<p>It is also possible in a CTH to hook in behaviour after
237
<seealso marker="common_test#Module:init_per_suite-1">init_per_suite</seealso>,
238
<seealso marker="common_test#Module:init_per_suite-1">init_per_group</seealso>,
239
<seealso marker="common_test#Module:init_per_suite-1">end_per_testcase</seealso>,
240
<seealso marker="common_test#Module:init_per_suite-1">end_per_group</seealso> and
241
<seealso marker="common_test#Module:init_per_suite-1">end_per_suite</seealso>.
242
This is done in the CTH functions called post_<name of function>.
243
All of these function take the same four arguments: <c>Name</c>,
244
<c>Config</c>, <c>Return</c> and <c>CTHState</c>. <c>Config</c> in this
245
case is the same <c>Config</c> as the testcase is called with.
246
<c>Return</c> is the value returned by the testcase. If the testcase
247
failed by crashing, <c>Return</c> will be
248
<c>{'EXIT',{{Error,Reason},Stacktrace}}</c>.</p>
250
<p>The return value of the CTH function is always a combination of an
251
result for the suite/group/test and an updated <c>CTHState</c>. If
252
you want the callback to not affect the outcome of the test you should
253
return the <c>Return</c> data as it is given to the CTH. You can also
254
modify the result of the test. By returning the <c>Config</c> list
255
with the <c>tc_status</c> element removed you can recover from a test
256
failure. As in all the pre hooks, it is also possible to fail/skip
257
the test case in the post hook. Example: </p>
259
<code>post_end_per_testcase(_TC, Config, {'EXIT',{_,_}}, CTHState) ->
260
case db:check_consistency() of
262
%% DB is good, pass the test.
263
{proplists:delete(tc_status, Config), CTHState};
265
%% DB is not good, mark as skipped instead of failing
266
{{skip, "DB is inconsisten!"}, CTHState}
268
post_end_per_testcase(_TC, Config, Return, CTHState) ->
269
%% Do nothing if tc does not crash.
270
{Return, CTHState}.</code>
272
<note>Recovering from a testcase failure using CTHs should only be done as
273
a last resort. If used wrongly it could become very difficult to
274
determine which tests pass or fail in a test run</note>
278
<marker id="skip_n_fail"/>
280
<title>Skip and Fail hooks</title>
282
After any post hook has been executed for all installed CTHs,
283
<seealso marker="ct_hooks#Module:on_tc_fail-3">on_tc_fail</seealso>
284
or <seealso marker="ct_hooks#Module:on_tc_fail-3">on_tc_skip</seealso>
285
might be called if the testcase failed or was skipped
286
respectively. You cannot affect the outcome of the tests any further at
293
<marker id="example"/>
295
<title>Example CTH</title>
296
<p>The CTH below will log information about a test run into a format
297
parseable by <seealso marker="kernel:file#consult-1">file:consult/1</seealso>.
299
<code>%%% @doc Common Test Example Common Test Hook module.
300
-module(example_cth).
306
-export([pre_init_per_suite/3]).
307
-export([post_init_per_suite/4]).
308
-export([pre_end_per_suite/3]).
309
-export([post_end_per_suite/4]).
311
-export([pre_init_per_group/3]).
312
-export([post_init_per_group/4]).
313
-export([pre_end_per_group/3]).
314
-export([post_end_per_group/4]).
316
-export([pre_init_per_testcase/3]).
317
-export([post_end_per_testcase/4]).
319
-export([on_tc_fail/3]).
320
-export([on_tc_skip/3]).
322
-export([terminate/1]).
324
-record(state, { file_handle, total, suite_total, ts, tcs, data }).
326
%% @doc Return a unique id for this CTH.
328
proplists:get_value(filename, Opts, "/tmp/file.log").
330
%% @doc Always called before any other callback function. Use this to initiate
333
{ok,D} = file:open(Id,[write]),
334
#state{ file_handle = D, total = 0, data = [] }.
336
%% @doc Called before init_per_suite is called.
337
pre_init_per_suite(Suite,Config,State) ->
338
{Config, State#state{ suite_total = 0, tcs = [] }}.
340
%% @doc Called after init_per_suite.
341
post_init_per_suite(Suite,Config,Return,State) ->
344
%% @doc Called before end_per_suite.
345
pre_end_per_suite(Suite,Config,State) ->
348
%% @doc Called after end_per_suite.
349
post_end_per_suite(Suite,Config,Return,State) ->
350
Data = {suites, Suite, State#state.suite_total, lists:reverse(State#state.tcs)},
351
{Return, State#state{ data = [Data | State#state.data] ,
352
total = State#state.total + State#state.suite_total } }.
354
%% @doc Called before each init_per_group.
355
pre_init_per_group(Group,Config,State) ->
358
%% @doc Called after each init_per_group.
359
post_init_per_group(Group,Config,Return,State) ->
362
%% @doc Called after each end_per_group.
363
pre_end_per_group(Group,Config,State) ->
366
%% @doc Called after each end_per_group.
367
post_end_per_group(Group,Config,Return,State) ->
370
%% @doc Called before each test case.
371
pre_init_per_testcase(TC,Config,State) ->
372
{Config, State#state{ ts = now(), total = State#state.suite_total + 1 } }.
374
%% @doc Called after each test case.
375
post_end_per_testcase(TC,Config,Return,State) ->
376
TCInfo = {testcase, TC, Return, timer:now_diff(now(), State#state.ts)},
377
{Return, State#state{ ts = undefined, tcs = [TCInfo | State#state.tcs] } }.
379
%% @doc Called after post_init_per_suite, post_end_per_suite, post_init_per_group,
380
%% post_end_per_group and post_end_per_testcase if the suite, group or test case failed.
381
on_tc_fail(TC, Reason, State) ->
384
%% @doc Called when a test case is skipped by either user action
385
%% or due to an init function failing.
386
on_tc_skip(TC, Reason, State) ->
389
%% @doc Called when the scope of the CTH is done
391
io:format(State#state.file_handle, "~p.~n",
392
[{test_run, State#state.total, State#state.data}]),
393
file:close(State#state.file_handle),