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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE chapter SYSTEM "chapter.dtd">
<chapter>
<header>
<copyright>
<year>2004</year><year>2013</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>External Configuration Data</title>
<prepared>Siri Hansen, Peter Andersson</prepared>
<docno></docno>
<date></date>
<rev></rev>
<file>config_file_chapter.xml</file>
</header>
<marker id="top"></marker>
<section>
<title>General</title>
<p>To avoid hard coding data values related to the test and/or SUT (System
Under Test) in the test suites, the data may instead be specified by means
of configuration files or strings that Common Test reads before
the start of a test run. External configuration data makes it possible to
change test properties without having to modify the actual test suites
using the data. Examples of configuration data:</p>
<list>
<item>Addresses to the test plant or other instruments</item>
<item>User login information</item>
<item>Names of files needed by the test</item>
<item>Names of programs that should be executed during the test</item>
<item>Any other variable needed by the test</item>
</list>
</section>
<section>
<title>Syntax</title>
<p>A configuration file can contain any number of elements of the type:</p>
<pre>
{CfgVarName,Value}.</pre>
<p>where</p>
<pre>
CfgVarName = atom()
Value = term() | [{CfgVarName,Value}]</pre>
</section>
<section>
<title>Requiring and reading configuration data</title>
<marker id="require_config_data"></marker>
<p>In a test suite, one must <em>require</em> that a configuration
variable (<c>CfgVarName</c> in the definition above) exists before
attempting to read the associated value in a test case or config function.</p>
<p><c>require</c> is an assert statement that can be part of the <seealso
marker="write_test_chapter#suite">test suite info function</seealso> or
<seealso marker="write_test_chapter#info_function">test case info
function</seealso>. If the required variable is not available, the
test is skipped (unless a default value has been specified, see the
<seealso marker="write_test_chapter#info_function">test case info
function</seealso> chapter for details). There is also a function
<seealso marker="ct#require-1"><c>ct:require/1/2</c></seealso> which can be called from a test case
in order to check if a specific variable is available. The return
value from this function must be checked explicitly and appropriate
action be taken depending on the result (e.g. to skip the test case
if the variable in question doesn't exist).</p>
<p>A <c>require</c> statement in the test suite info- or test case
info-list should look like this:
<c>{require,CfgVarName}</c> or <c>{require,AliasName,CfgVarName}</c>.
The arguments <c>AliasName</c> and <c>CfgVarName</c> are the same as the
arguments to <seealso marker="ct#require-1"><c>ct:require/1/2</c></seealso> which are described in the
reference manual for <seealso marker="ct">ct</seealso>.
<c>AliasName</c> becomes an alias for the configuration variable,
and can be used as reference to the configuration data value.
The configuration variable may be associated with an
arbitrary number of alias names, but each name must be unique within
the same test suite. There are two main uses for alias names:</p>
<list>
<item>They may be introduced to identify connections (see below).</item>
<item>They may used to help adapt configuration data to a test suite
(or test case) and improve readability.</item>
</list>
<p>To read the value of a config variable, use the function
<seealso marker="ct#get_config-1"><c>get_config/1/2/3</c></seealso>
which is also described in the reference
manual for <seealso marker="ct">ct</seealso>.</p>
<p>Example:</p>
<pre>
suite() ->
[{require, domain, 'CONN_SPEC_DNS_SUFFIX'}].
...
testcase(Config) ->
Domain = ct:get_config(domain),
...</pre>
</section>
<section>
<title>Using configuration variables defined in multiple files</title>
<p>If a configuration variable is defined in multiple files and you
want to access all possible values, you may use the <seealso marker="ct#get_config-3"><c>ct:get_config/3</c></seealso>
function and specify <c>all</c> in the options list. The values will then
be returned in a list and the order of the elements corresponds to the order
that the config files were specified at startup. Please see
the <seealso marker="ct">ct</seealso> reference manual for details.</p>
</section>
<section>
<title>Encrypted configuration files</title>
<marker id="encrypted_config_files"></marker>
<p>It is possible to encrypt configuration files containing sensitive data
if these files must be stored in open and shared directories.</p>
<p>Call <seealso marker="ct#encrypt_config_file-2"><c>ct:encrypt_config_file/2/3</c></seealso> to have Common Test encrypt a
specified file using the DES3 function in the OTP <c>crypto</c> application.
The encrypted file can then be used as a regular configuration file,
in combination with other encrypted files or normal text files. The key
for decrypting the configuration file must be provided when running the test,
however. This can be done by means of the <c>decrypt_key</c> or
<c>decrypt_file</c> flag/option, or a key file in a predefined location.</p>
<p>Common Test also provides decryption functions,
<seealso marker="ct#decrypt_config_file-2"><c>ct:decrypt_config_file/2/3</c></seealso>, for recreating the original text
files.</p>
<p>Please see the <seealso marker="ct">ct</seealso> reference manual for
more information.</p>
</section>
<section>
<title>Opening connections by using configuration data</title>
<p>There are two different methods for opening a connection
by means of the support functions in e.g. <seealso marker="ct_ssh"><c>ct_ssh</c></seealso>, <seealso marker="ct_ftp"><c>ct_ftp</c></seealso>,
and <seealso marker="ct_telnet"><c>ct_telnet</c></seealso>:</p>
<list>
<item>Using a configuration target name (an alias) as reference.</item>
<item>Using the configuration variable as reference.</item>
</list>
<p>When a target name is used for referencing the configuration data
(that specifies the connection to be opened), the same name may be used
as connection identity in all subsequent calls related to the connection
(also for closing it). It's only possible to have one open connection
per target name. If attempting to open a new connection using a name
already associated with an open connection, Common Test will
return the already existing handle so that the previously opened connection
will be used. This is a practical feature since it makes it possible to
call the function for opening a particular connection whenever
useful. An action like this will not necessarily open any new
connections unless it's required (which could be the case if e.g. the
previous connection has been closed unexpectedly by the server).
Another benefit of using named connections is that it's not
necessary to pass handle references around in the suite for these
connections.
</p>
<p>When a configuration variable name is used as reference to the data
specifying the connection, the handle returned as a result of opening
the connection must be used in all subsequent calls (also for closing
the connection). Repeated calls to the open function with the same
variable name as reference will result in multiple connections
being opened. This can be useful e.g. if a test case needs to open
multiple connections to the same server on the target node (using the
same configuration data for each connection).
</p>
</section>
<section>
<title>User specific configuration data formats</title>
<p>It is possible for the user to specify configuration data on a
different format than key-value tuples in a text file, as described
so far. The data can e.g. be read from arbitrary files, fetched from
the web over http, or requested from a user specific process.
To support this, Common Test provides a callback module plugin
mechanism to handle configuration data.</p>
<section>
<title>Default callback modules for handling configuration data</title>
<p>The Common Test application includes default callback modules
for handling configuration data specified in standard config files
(see above) and in xml files:</p>
<list>
<item>
<c>ct_config_plain</c> - for reading configuration files with
key-value tuples (standard format). This handler will be used to
parse configuration files if no user callback is specified.
</item>
<item>
<c>ct_config_xml</c> - for reading configuration data from XML
files.
</item>
</list>
</section>
<section>
<title>Using XML configuration files</title>
<p>This is an example of an XML configuration file:</p>
<pre><![CDATA[
<config>
<ftp_host>
<ftp>"targethost"</ftp>
<username>"tester"</username>
<password>"letmein"</password>
</ftp_host>
<lm_directory>"/test/loadmodules"</lm_directory>
</config>]]></pre>
<p>This configuration file, once read, will produce the same configuration
variables as the following text file:</p>
<pre>
{ftp_host, [{ftp,"targethost"},
{username,"tester"},
{password,"letmein"}]}.
{lm_directory, "/test/loadmodules"}.</pre>
</section>
<section>
<title>How to implement a user specific handler</title>
<p>The user specific handler can be written to handle special
configuration file formats. The parameter can be either file
name(s) or configuration string(s) (the empty list is valid).</p>
<p>The callback module implementing the handler is responsible for
checking correctness of configuration strings.</p>
<p>To perform validation of the configuration strings, the callback module
should have the following function exported:</p>
<p><c>Callback:check_parameter/1</c></p>
<p>The input argument will be passed from Common Test, as defined in the test
specification or given as an option to <c>ct_run</c> or <c>ct:run_test</c>.</p>
<p>The return value should be any of the following values indicating if given
configuration parameter is valid:</p>
<list>
<item>
<c>{ok, {file, FileName}}</c> - parameter is a file name and
the file exists,
</item>
<item>
<c>{ok, {config, ConfigString}}</c> - parameter is a config string
and it is correct,
</item>
<item>
<c>{error, {nofile, FileName}}</c> - there is no file with the given
name in the current directory,
</item>
<item>
<c>{error, {wrong_config, ConfigString}}</c> - the configuration string
is wrong.
</item>
</list>
<p>To perform reading of configuration data - initially before the tests
start, or as a result of data being reloaded during test execution -
the following function should be exported from the callback module:</p>
<p><c>Callback:read_config/1</c></p>
<p>The input argument is the same as for the <c>check_parameter/1</c> function.</p>
<p>The return value should be either:</p>
<list>
<item>
<c>{ok, Config}</c> - if the configuration variables are read successfully,
</item>
<item>
<c>{error, {Error, ErrorDetails}}</c> - if the callback module fails to
proceed with the given configuration parameters.
</item>
</list>
<p><c>Config</c> is the proper Erlang key-value list, with possible
key-value sublists as values, like for the configuration file
example above:</p>
<pre>
[{ftp_host, [{ftp, "targethost"}, {username, "tester"}, {password, "letmein"}]},
{lm_directory, "/test/loadmodules"}]</pre>
</section>
</section>
<section>
<title>Examples of configuration data handling</title>
<p>A config file for using the FTP client to access files on a remote
host could look like this:</p>
<pre>
{ftp_host, [{ftp,"targethost"},
{username,"tester"},
{password,"letmein"}]}.
{lm_directory, "/test/loadmodules"}.</pre>
<p>The XML version shown in the chapter above can also be used, but it should be
explicitly specified that the <c>ct_config_xml</c> callback module is to be
used by Common Test.</p>
<p>Example of how to assert that the configuration data is available and
use it for an FTP session:</p>
<pre>
init_per_testcase(ftptest, Config) ->
{ok,_} = ct_ftp:open(ftp),
Config.
end_per_testcase(ftptest, _Config) ->
ct_ftp:close(ftp).
ftptest() ->
[{require,ftp,ftp_host},
{require,lm_directory}].
ftptest(Config) ->
Remote = filename:join(ct:get_config(lm_directory), "loadmodX"),
Local = filename:join(?config(priv_dir,Config), "loadmodule"),
ok = ct_ftp:recv(ftp, Remote, Local),
...</pre>
<p>An example of how the above functions could be rewritten
if necessary to open multiple connections to the FTP server:</p>
<pre>
init_per_testcase(ftptest, Config) ->
{ok,Handle1} = ct_ftp:open(ftp_host),
{ok,Handle2} = ct_ftp:open(ftp_host),
[{ftp_handles,[Handle1,Handle2]} | Config].
end_per_testcase(ftptest, Config) ->
lists:foreach(fun(Handle) -> ct_ftp:close(Handle) end,
?config(ftp_handles,Config)).
ftptest() ->
[{require,ftp_host},
{require,lm_directory}].
ftptest(Config) ->
Remote = filename:join(ct:get_config(lm_directory), "loadmodX"),
Local = filename:join(?config(priv_dir,Config), "loadmodule"),
[Handle | MoreHandles] = ?config(ftp_handles,Config),
ok = ct_ftp:recv(Handle, Remote, Local),
...</pre>
</section>
<section>
<title>Example of user specific configuration handler</title>
<p>A simple configuration handling driver which will ask an external server for
configuration data can be implemented this way:</p>
<pre>
-module(config_driver).
-export([read_config/1, check_parameter/1]).
read_config(ServerName)->
ServerModule = list_to_atom(ServerName),
ServerModule:start(),
ServerModule:get_config().
check_parameter(ServerName)->
ServerModule = list_to_atom(ServerName),
case code:is_loaded(ServerModule) of
{file, _}->
{ok, {config, ServerName}};
false->
case code:load_file(ServerModule) of
{module, ServerModule}->
{ok, {config, ServerName}};
{error, nofile}->
{error, {wrong_config, "File not found: " ++ ServerName ++ ".beam"}}
end
end.</pre>
<p>The configuration string for this driver may be "config_server", if the
config_server.erl module below is compiled and exists in the code path
during test execution:</p>
<pre>
-module(config_server).
-export([start/0, stop/0, init/1, get_config/0, loop/0]).
-define(REGISTERED_NAME, ct_test_config_server).
start()->
case whereis(?REGISTERED_NAME) of
undefined->
spawn(?MODULE, init, [?REGISTERED_NAME]),
wait();
_Pid->
ok
end,
?REGISTERED_NAME.
init(Name)->
register(Name, self()),
loop().
get_config()->
call(self(), get_config).
stop()->
call(self(), stop).
call(Client, Request)->
case whereis(?REGISTERED_NAME) of
undefined->
{error, {not_started, Request}};
Pid->
Pid ! {Client, Request},
receive
Reply->
{ok, Reply}
after 4000->
{error, {timeout, Request}}
end
end.
loop()->
receive
{Pid, stop}->
Pid ! ok;
{Pid, get_config}->
{D,T} = erlang:localtime(),
Pid !
[{localtime, [{date, D}, {time, T}]},
{node, erlang:node()},
{now, erlang:now()},
{config_server_pid, self()},
{config_server_vsn, ?vsn}],
?MODULE:loop()
end.
wait()->
case whereis(?REGISTERED_NAME) of
undefined->
wait();
_Pid->
ok
end.</pre>
<p>In this example, the handler also provides the ability to dynamically reload
configuration variables. If <c>ct:reload_config(localtime)</c> is called from
the test case function, all variables loaded with <c>config_driver:read_config/1</c>
will be updated with their latest values, and the new value for variable
<c>localtime</c> will be returned.</p>
</section>
</chapter>
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