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    <title>ct_property_test</title>
    <prepared></prepared>
    <responsible></responsible>
    <docno></docno>
    <approved></approved>
    <checked></checked>
    <date></date>
    <rev>A</rev>
    <file>ct_property_test.xml</file>
  </header>
  <module since="OTP 17.3">ct_property_test</module>
  <modulesummary>Support in Common Test for running property-based tests.</modulesummary>

  <description>

    <p>This module helps running property-based tests in the
    <c>Common Test</c> framework. One (or more) of the property testing tools
    </p>
    <list>
      <item><url href="http://www.quviq.com">QuickCheck</url>,</item>
      <item><url href="https://proper-testing.github.io">PropEr</url> or</item>
      <item><url href="https://github.com/krestenkrab/triq">Triq</url></item>
    </list>
    <p>
      is assumed to be installed.
    </p>

    <p>The idea with this module is to have a <c>Common Test</c> test suite calling
    a property testing tool with special property test suites as defined by that tool.
    The tests
    are collected in the <c>test</c> directory of the application. The
    <c>test</c> directory has a subdirectory <c>property_test</c>, where
    everything needed for the property tests are collected.
    The usual Erlang application directory structure is assumed.
    </p>

    <p>A typical <c>Common Test</c> test suite using <c>ct_property_test</c>
    is organized as follows:</p>

    <code>
-module(my_prop_test_SUITE).
-compile(export_all).

-include_lib("common_test/include/ct.hrl").

 all() -&gt; [prop_ftp_case].

 init_per_suite(Config) -&gt;
     ct_property_test:init_per_suite(Config).

 %%%---- test case
 prop_ftp_case(Config) -&gt;
     ct_property_test:quickcheck(
       ftp_simple_client_server:prop_ftp(),
       Config
      ).</code>
      <p>and the the property test module (in this example <c>ftp_simple_client_server.erl</c>)
      as almost a usual property testing module
      (More examples are in <seeguide marker="ct_property_test_chapter">the User's Guide</seeguide>):</p>
      <code>
-module(ftp_simple_client_server).	
-export([prop_ftp/0...]).

-include_lib("common_test/include/ct_property_test.hrl").

prop_ftp() -&gt;
    ?FORALL( ....
      </code>
  </description>

  <funcs>
    <func>
    <name since="OTP 17.3">init_per_suite(Config) -&gt; Config | {skip, Reason}</name>
    <fsummary>Initializes and extends Config for property testing.</fsummary>
      <desc><marker id="init_per_suite-1"/>
        <p>Initializes and extends  <c>Config</c> for property based testing.</p>

        <p>This function investigates if support is available for either
        <url href="http://www.quviq.com">QuickCheck</url>,
	<url href="https://proper-testing.github.io">PropEr</url>
	or <url href="https://github.com/krestenkrab/triq">Triq</url> and compiles the
	properties with the first tool found.
	It is supposed to be called in the <c>init_per_suite/1</c> function
	in a CommonTest test suite.
	</p>
	<p>Which tools to check for, and in which order could be set with the option
	<c>{prop_tools, list(eqc|proper|triq)}</c>
	in the CommonTest configuration <c>Config</c>. The default value is
	<c>[eqc, proper, triq]</c> with <c>eqc</c> being the first one searched for.
	</p>
	<p>If no support is found for any tool, this function returns
	<c>{skip, Explanation}</c>.
	</p>
	<p>If support is found, the option <c>{property_test_tool,ToolModule}</c> with
	the selected tool main module name (<c>eqc</c>, <c>proper</c> or <c>triq</c>)
        is added to the list <c>Config</c> which then is returned.
	</p>
        <p>The property tests are assumed to be in a subdirectory named
	<c>property_test</c>.
	All found Erlang files in that directory are compiled with one of the macros
	<c>'EQC'</c>, <c>'PROPER'</c> or <c>'TRIQ'</c> set, depending on which tool
	that is first found. This could make parts of the Erlang property tests
	code to be included or excluded with the macro directives
	<c>-ifdef(Macro).</c> or <c>-ifndef(Macro).</c>.
	</p>
	<p>The file(s) in the <c>property_test</c> subdirectory could, or should,
	include the ct_property_test include file:
	</p>
	<code>
-include_lib("common_test/include/ct_property_test.hrl").
	</code>
	<p>This included file will:
	</p>
	<list>
	  <item>Include the correct tool's include file</item>
	  <item>Set the macro <c>'MOD_eqc'</c> to the correct module name for the
	  selected tool. That is, the macro <c>'MOD_eqc'</c> is set to either
	  <c>eqc</c>, <c>proper</c> or <c>triq</c>.
	  </item>
	</list>
      </desc>
    </func>

    <func>
      <name since="OTP 17.3">quickcheck(Property, Config) -&gt; true | {fail, Reason}</name>
      <fsummary>Calls quickcheck and returns the result in a form suitable for
      Common Test.</fsummary>
      <desc>
      <p>Calls the selected tool's function for running the <c>Property</c>. It is usually and
      by historical reasons called quickcheck, and that is why that name is used in
      this module (<c>ct_property_test</c>).
      </p>
      <p>The result is returned in a form suitable for <c>Common Test</c> test suites.
      </p>
      <p>This function is intended to be called in test cases in test suites.
      </p>
      </desc>
    </func>

    <func>
      <name since="">present_result(Module, Cmds, Triple, Config) -> Result</name>
      <fsummary>Presents the result of statem property testing</fsummary>
      <desc>
      <p>Same as <seemfa marker="#present_result/5"><c>present_result(Module, Cmds, Triple, Config, [])</c></seemfa>
      </p>
      </desc>
    </func>

    <func>
      <name since="">present_result(Module, Cmds, Triple, Config, Options) -> Result</name>
      <fsummary>Presents the result of statem property testing</fsummary>
      <type>
	<v>Module = module()</v>
	<d></d>
	
	<v>Cmds =</v>
	<d>the list of commands generated by the property testing tool, for example
	  by proper:commands/1 or by proper:parallel_commands/1
	</d>

	<v>Triple =</v>
	<d>the output from for example proper:run_commands/2 or proper:run_parallel_commands/2</d>

	<v>Config =</v>
	<d>the Common Test <seemfa marker="common_test#Module:Testcase/1">Config</seemfa> in test cases.</d>

	<v>Options = [present_option()]</v>
	<v>present_option() = {print_fun, fun(Format,Args)}</v>
	<v>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;| {spec, StatisticsSpec}</v>
	<d>The <c>print_fun</c> defines which function to do the actual printout. The default is
	<seemfa marker="ct#log/2">ct:log/2</seemfa>.
	The <c>spec</c> defines what statistics are to be printed<!--, see the
	<seeguide marker="ct_property_test_chapter#spec_present_result">User's Guide</seeguide>-->
	</d>

	<v>Result = boolean()</v>
	<d>Is <c>false</c> if the test failed and is <c>true</c> if the test passed</d>
      </type>
      <desc>
      <p>Presents the result of <i>stateful (statem) property testing</i> using the aggregate function in
      PropEr, QuickCheck or other similar property testing tool.
      </p>
      <p>It is assumed to be called inside the property called by
      <seemfa marker="#quickcheck/2">quickcheck/2</seemfa>:</p>
      <code>
...
RunResult = run_parallel_commands(?MODULE, Cmds),
ct_property_test:present_result(?MODULE, Cmds, RunResult, Config)	
...
      </code>
      <p>See the <seeguide marker="ct_property_test_chapter#stateful1">User's Guide</seeguide> for
      an example of the usage and of the default printout.
      </p>
      <p>The <c>StatisticsSpec</c> is a list of the tuples:</p>
      <list>
	<item><c>{Title::string(), CollectFun::fun/1}</c></item>
	<item><c>{Title::string(), FrequencyFun::/0, CollectFun::fun/1}</c></item>
      </list>
      <p>Each tuple will produce one table in the order of their places in the list.</p>
      <list>
	<item><c>Title</c> will be the title of one result table</item>

	<item><c>CollectFun</c> is called with one argument: the <c>Cmds</c>. It should return
	a list of the values to be counted. The following pre-defined functions exist:
	<list>
	  <item><c>ct_property_test:cmnd_names/1</c> returns a list of commands (function calls) generated in the <c>Cmnd</c>
	  sequence, without Module, Arguments and other details.</item>
	  <item><c>ct_property_test:num_calls/1</c> returns a list of the length of commands lists</item>
	  <item><c>ct_property_test:sequential_parallel/1</c> returns a list with information about sequential and
	  parallel parts from <c>Tool:parallel_commands/1,2</c></item>
	</list>
	</item>

	<item><c>FrequencyFun/0</c> returns a fun/1 which is supposed to take a list of items as input,
	and return an iolist wich will be printed as the table. Per default, the number of each item is counted
	and the percentage is printed for each.  The list [a,b,a,a,c] could for example return
	<pre>
 ["a 60%\n","b 20%\n","c 20%\n"]</pre>
        which will be printed by the <c>print_fun</c>.
	The default <c>print_fun</c> will print it as: 
	<pre>
 a 60%
 b 20%
 c 20%</pre>
	</item>
      </list>
      <p>The default <c>StatisticsSpec</c> is:</p>
      <list>
	<item>For sequential commands:
	<code>
[{"Function calls", fun cmnd_names/1},
 {"Length of command sequences", fun print_frequency_ranges/0,
                                                  fun num_calls/1}]
	</code></item>
	<item>For parallel commands:
	<code>
[{"Distribution sequential/parallel", fun sequential_parallel/1},
 {"Function calls", fun cmnd_names/1},
 {"Length of command sequences", fun print_frequency_ranges/0,
                                                  fun num_calls/1}]
	</code></item>
      </list>
      </desc>
    </func>

  </funcs>

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