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<!DOCTYPE chapter SYSTEM "chapter.dtd">
<chapter>
<header>
<copyright>
<year>2003</year><year>2009</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
The contents of this file are subject to the Erlang Public License,
Version 1.1, (the "License"); you may not use this file except in
compliance with the License. You should have received a copy of the
Erlang Public License along with this software. If not, it can be
retrieved online at http://www.erlang.org/.
Software distributed under the License is distributed on an "AS IS"
basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
the License for the specific language governing rights and limitations
under the License.
</legalnotice>
<title>Common Test Basics</title>
<prepared>Kenneth Lundin, Peter Andersson</prepared>
<docno></docno>
<date>2003-10-21</date>
<rev></rev>
<file>basics_chapter.xml</file>
</header>
<marker id="basics"></marker>
<section>
<title>Introduction</title>
<p>The <em>Common Test</em> framework (CT) is a tool which supports
implementation and automated execution of test cases towards arbitrary
types of target systems. The CT framework is based on the OTP Test
Server and it's the main tool being used in all testing- and verification
activities that are part of Erlang/OTP system development- and maintenance.
</p>
<p>Test cases can be executed individually or in batches. Common Test
also features a distributed testing mode with central control and logging
(a feature that makes it possible to test multiple systems independently in
one common session, useful e.g. for running automated large-scale regression
tests).
</p>
<p>
The SUT (System Under Test) may consist of one or several target
nodes. CT contains a generic test server which, together with
other test utilities, is used to perform test case execution.
It is possible to start the tests from a GUI or from the OS- or
Erlang shell. <em>Test suites</em> are files (Erlang
modules) that contain the <em>test cases</em> (Erlang functions)
to be executed. <em>Support modules</em> provide functions
that the test cases utilize in order to carry out the tests.
</p>
<p>In a black-box testing scenario, CT based test programs connect to
the target system(s) via standard O&M and CLI protocols. CT
provides implementations of, and wrapper interfaces to, some of these
protocols (most of which exist as stand-alone components and
applications in OTP). The wrappers simplify configuration and add
verbosity for logging purposes. CT will be continously extended with
useful support modules. (Note however that it's
a straightforward task to use any arbitrary Erlang/OTP component
for testing purposes with Common Test, without needing a CT wrapper
for it. It's as simple as calling Erlang functions). There
are a number of target independent interfaces supported in CT, such as
Generic Telnet, FTP, etc, which can be specialized or used
directly for controlling instruments, traffic load generators, etc.
</p>
<p>Common Test is also a very useful tool for white-box testing Erlang
code (e.g. module testing), since the test programs can call exported Erlang
functions directly and there's very little overhead required for
implementing basic test suites and executing simple tests. For black-box
testing Erlang software, Erlang RPC as well as standard O&M interfaces
can for example be used.
</p>
<p>A test case can handle several connections towards one or
several target systems, instruments and traffic generators in
parallel in order to perform the necessary actions for a
test. The handling of many connections in parallel is one of
the major strengths of Common Test (thanks to the efficient
support for concurrency in the Erlang runtime system - which CT users
can take great advantage of!).
</p>
</section>
<section>
<title>Test Suite Organisation</title>
<p>
The test suites are organized in test directories and each test suite
may have a separate data directory. Typically, these files and directories
are version controlled similarly to other forms of source code (possibly by
means of a version control system like GIT or Subversion). However, CT does
not itself put any requirements on (or has any form of awareness of)
possible file and directory versions.
</p>
</section>
<section>
<title>Support Libraries</title>
<p>
Support libraries contain functions that are useful for all test suites,
or for test suites in a specific functional area or subsystem.
In addition to the general support libraries provided by the
CT framework, and the various libraries and applications provided by
Erlang/OTP, there might also be a need for customized (user specific)
support libraries.
</p>
</section>
<section>
<title>Suites and Test Cases</title>
<p>
Testing is performed by running test suites (sets of test cases) or
individual test cases. A test suite is implemented as an Erlang module named
<c><![CDATA[<suite_name>_SUITE.erl]]></c> which contains a number of test cases.
A test case is an Erlang function which tests one or more things.
The test case is the smallest unit that the CT test server deals with.
</p>
<p>
Subsets of test cases, called test case groups, may also be defined. A test case
group can have execution properties associated with it. Execution properties
specify whether the test cases in the group should be executed in
random order, in parallel, in sequence, and if the execution of the group
should be repeated. Test case groups may also be nested (i.e. a group may,
besides test cases, contain sub-groups).
</p>
<p>
Besides test cases and groups, the test suite may also contain configuration
functions. These functions are meant to be used for setting up (and verifying)
environment and state on the SUT (and/or the CT host node), required for
the tests to execute correctly. Examples of operations: Opening a connection
to the SUT, initializing a database, running an installation script, etc.
Configuration may be performed per suite, per test case group and per
individual test case.
</p>
<p>
The test suite module must conform to a
<seealso marker="common_test">callback interface</seealso>
specified by the CT test server. See the
<seealso marker="write_test_chapter#intro">Writing Test Suites</seealso> chapter
for more information.
</p>
<p>
A test case is considered successful if it returns to the caller, no matter
what the returned value is. A few return values have special meaning however
(such as <c>{skip,Reason}</c> which indicates that the test case is skipped,
<c>{comment,Comment}</c> which prints a comment in the log for the test case and
<c>{save_config,Config}</c> which makes the CT test server pass <c>Config</c> to
the next test case).
A test case failure is specified as a runtime error (a crash), no matter what
the reason for termination is. If you use Erlang pattern matching effectively,
you can take advantage of this property. The result will be concise and
readable test case functions that look much more like scripts than actual programs.
Simple example:
</p>
<pre>
session(_Config) ->
{started,ServerId} = my_server:start(),
{clients,[]} = my_server:get_clients(ServerId),
MyId = self(),
connected = my_server:connect(ServerId, MyId),
{clients,[MyId]} = my_server:get_clients(ServerId),
disconnected = my_server:disconnect(ServerId, MyId),
{clients,[]} = my_server:get_clients(ServerId),
stopped = my_server:stop(ServerId).
</pre>
<p>
As a test suite runs, all information (including output to <c>stdout</c>) is
recorded in several different log files. A minimum of information is displayed
in the user console (only start and stop information, plus a note
for each failed test case).
</p>
<p>
The result from each test case is recorded in a dedicated HTML log file, created
for the particular test run. An overview page displays each test case represented
by row in a table showing total execution time, whether the case was successful,
failed or skipped, plus an optional user comment. (For a failed test case, the
reason for termination is also printed in the comment field). The overview page
has a link to each test case log file, providing simple navigation with any standard
HTML browser.
</p>
</section>
<section>
<title>External Interfaces</title>
<p>
The CT test server requires that the test suite defines and exports the
following mandatory or optional callback functions:
</p>
<taglist>
<tag>all()</tag>
<item>Returns a list of all test cases and groups in the suite. (Mandatory)</item>
<tag>suite()</tag>
<item>Info function used to return properties for the suite. (Optional)</item>
<tag>groups()</tag>
<item>For declaring test case groups. (Optional)</item>
<tag>init_per_suite(Config)</tag>
<item>Suite level configuration function, executed before the first
test case. (Optional)</item>
<tag>end_per_suite(Config)</tag>
<item>Suite level configuration function, executed after the last
test case. (Optional)</item>
<tag>group(GroupName)</tag>
<item>Info function used to return properties for a test case group. (Optional)</item>
<tag>init_per_group(GroupName, Config)</tag>
<item>Configuration function for a group, executed before the first
test case. (Optional)</item>
<tag>end_per_group(GroupName, Config)</tag>
<item>Configuration function for a group, executed after the last
test case. (Optional)</item>
<tag>init_per_testcase(TestCase, Config)</tag>
<item>Configuration function for a testcase, executed before each
test case. (Optional)</item>
<tag>end_per_testcase(TestCase, Config)</tag>
<item>Configuration function for a testcase, executed after each
test case. (Optional)</item>
</taglist>
<p>
For each test case the CT test server expects these functions:
</p>
<taglist>
<tag>Testcasename()</tag>
<item>Info function that returns a list of test case properties. (Optional)</item>
<tag>Testcasename(Config)</tag>
<item>The actual test case function.</item>
</taglist>
</section>
</chapter>
