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:
A configuration file can contain any number of elements of the type:
{CfgVarName,Value}.
where
CfgVarName = atom()
Value = term() | [{CfgVarName,Value}]
In a test suite, one must require that a configuration
variable (
A
To read the value of a config variable, use the function
Example:
suite() ->
[{require, domain, 'CONN_SPEC_DNS_SUFFIX'}].
...
testcase(Config) ->
Domain = ct:get_config(domain),
...
If a configuration variable is defined in multiple files and you
want to access all possible values, you may use the
It is possible to encrypt configuration files containing sensitive data if these files must be stored in open and shared directories.
Call
Common Test also provides decryption functions,
Please see the
There are two different methods for opening a connection
by means of the support functions in e.g.
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.
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).
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.
The Common Test application includes default callback modules for handling configuration data specified in standard config files (see above) and in xml files:
This is an example of an XML configuration file:
"targethost"
"tester"
"letmein"
"/test/loadmodules"
]]>
This configuration file, once read, will produce the same configuration variables as the following text file:
{ftp_host, [{ftp,"targethost"},
{username,"tester"},
{password,"letmein"}]}.
{lm_directory, "/test/loadmodules"}.
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).
The callback module implementing the handler is responsible for checking correctness of configuration strings.
To perform validation of the configuration strings, the callback module should have the following function exported:
The input argument will be passed from Common Test, as defined in the test
specification or given as an option to
The return value should be any of the following values indicating if given configuration parameter is valid:
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:
The input argument is the same as for the
The return value should be either:
[{ftp_host, [{ftp, "targethost"}, {username, "tester"}, {password, "letmein"}]},
{lm_directory, "/test/loadmodules"}]
A config file for using the FTP client to access files on a remote host could look like this:
{ftp_host, [{ftp,"targethost"},
{username,"tester"},
{password,"letmein"}]}.
{lm_directory, "/test/loadmodules"}.
The XML version shown in the chapter above can also be used, but it should be
explicitly specified that the
Example of how to assert that the configuration data is available and use it for an FTP session:
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),
...
An example of how the above functions could be rewritten if necessary to open multiple connections to the FTP server:
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),
...
A simple configuration handling driver which will ask an external server for configuration data can be implemented this way:
-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.
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:
-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.
In this example, the handler also provides the ability to dynamically reload
configuration variables. If