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diff --git a/lib/eunit/doc/overview.edoc b/lib/eunit/doc/overview.edoc new file mode 100644 index 0000000000..2583f0be25 --- /dev/null +++ b/lib/eunit/doc/overview.edoc @@ -0,0 +1,1028 @@ + + -*- html -*- + + EUnit overview page + +@title EUnit - a Lightweight Unit Testing Framework for Erlang + +@author Richard Carlsson <[email protected]> + [http://user.it.uu.se/~richardc/] +@author Micka�l R�mond <[email protected]> + [http://www.process-one.net/] +@copyright 2004-2007 Micka�l R�mond, Richard Carlsson +@version {@version}, {@date} {@time} + +@doc EUnit is a unit testing framework for Erlang. It is very powerful +and flexible, is easy to use, and has small syntactical overhead. + +<ul> +<li>{@section Unit testing}</li> +<li>{@section Terminology}</li> +<li>{@section Getting started}</li> +<li>{@section EUnit macros}</li> +<li>{@section EUnit test representation}</li> +</ul> + +EUnit builds on ideas from the family of unit testing frameworks for +Object Oriented languages that originated with JUnit by Beck and Gamma +(and Beck's previous framework SUnit for Smalltalk). However, EUnit uses +techniques more adapted to functional and concurrent programming, and is +typically less verbose than its relatives. + +Although EUnit uses many preprocessor macros, they have been designed to +be as nonintrusive as possible, and should not cause conflicts with +existing code. Adding EUnit tests to a module should thus not normally +require changing existing code. Furthermore, tests that only exercise +the exported functions of a module can always be placed in a completely +separate module, avoiding any conflicts entirely. + +== Unit testing == + +Unit Testing is testing of individual program "units" in relative +isolation. There is no particular size requirement: a unit can be a +function, a module, a process, or even a whole application, but the most +typical testing units are individual functions or modules. In order to +test a unit, you specify a set of individual tests, set up the smallest +necessary environment for being able to run those tests (often, you +don't need to do any setup at all), you run the tests and collect the +results, and finally you do any necessary cleanup so that the test can +be run again later. A Unit Testing Framework tries to help you in each +stage of this process, so that it is easy to write tests, easy to run +them, and easy to see which tests failed (so you can fix the bugs). + +=== Advantages of unit testing === + +<dl> + <dt>Reduces the risks of changing the program</dt> + <dd>Most programs will be modified during their lifetime: bugs will be + fixed, features will be added, optimizations may become necessary, or + the code will need to be refactored or cleaned up in other ways to + make it easier to work with. But every change to a working program is + a risk of introducing new bugs - or reintroducing bugs that had + previously been fixed. Having a set of unit tests that you can run + with very little effort makes it easy to know that the code still + works as it should (this use is called <em>regression testing</em>; + see {@section Terminology}). This goes a long way to reduce the + resistance to changing and refactoring code.</dd> + <dt>Helps guide and speed up the development process</dt> + <dd>By focusing on getting the code to pass the tests, the programmer + can become more productive, not overspecify or get lost in premature + optimizations, and create code that is correct from the very beginning + (so-called <em>test-driven development</em>; see {@section + Terminology}).</dd> + <dt>Helps separate interface from implementation</dt> + <dd>When writing tests, the programmer may discover dependencies + (in order to get the tests to run) that ought not to be there, and + which need to be abstracted away to get a cleaner design. This helps + eliminate bad dependencies before they spread throughout the + code.</dd> + <dt>Makes component integration easier</dt> + <dd>By testing in a bottom-up fashion, beginning with the smallest + program units and creating a confidence in that they work as they + should, it becomes easier to test that a higher-level component, + consisting of several such units, also behaves according to + specification (known as <em>integration testing</em>; see {@section + Terminology}).</dd> + <dt>Is self-documenting</dt> + <dd>The tests can be read as documentation, typically showing both + examples of correct and incorrect usage, along with the expected + consequences.</dd> +</dl> + +== Terminology == + +<dl> + <dt>Unit testing</dt> + <dd>Testing that a program unit behaves as it is supposed to do (in + itself), according to its specifications. Unit tests have an important + function as regression tests, when the program later is modified for + some reason, since they check that the program still behaves according + to specification.</dd> + <dt>Regression testing</dt> + <dd>Running a set of tests after making changes to a program, to check + that the program behaves as it did before the changes (except, of + course, for any intentional changes in behaviour). Unit tests are + important as regression tests, but regression testing can involve more + than just unit testing, and may also test behaviour that might not be + part of the normal specification (such as bug-for-bug-compatibility). + </dd> + <dt>Integration testing</dt> + <dd>Testing that a number of individually developed program units + (assumed to already have been separately unit tested) work together as + expected. Depending on the system being developed, integration testing + may be as simple as "just another level of unit testing", but might + also involve other kinds of tests (compare <em>system testing</em>). +</dd> + <dt>System testing</dt> + <dd>Testing that a complete system behaves according to its + specification. Specifically, system testing should not require knowing + any details about the implementation. It typically involves testing + many different aspects of the system behaviour apart from the basic + functionality, such as performance, usability, and reliability.</dd> + <dt>Test-driven development</dt> + <dd>A program development technique where you continuously write tests + <em>before</em> you implement the code that is supposed to pass those + tests. This can help you focus on solving the right problems, and not + make a more complicated implementation than necessary, by letting the + unit tests determine when a program is "done": if it fulfils its + specifications, there is no need to keep adding functionality.</dd> + <dt>Mock object</dt> + <dd>Sometimes, testing some unit `A' (e.g., a function) requires that + it collaborates somehow with some other unit `B' (perhaps being passed + as an argument, or by reference) - but `B' has not been implemented + yet. A "mock object" - an object which, for the purposes of testing + `A', looks and behaves like a real `B' - might then be used instead. + (This is of course only useful if it would be significantly more work + to implement a real `B' than to create a mock object.)</dd> + <dt>Test case</dt> + <dd>A single, well-defined test, that somehow can be uniquely + identified. When executed, the test case either <em>passes</em> or + <em>fails</em>; the test report should identify exactly which test + cases failed.</dd> + <dt>Test suite</dt> + <dd>A collection of test cases, generally with a specific, common + target for testing, such as a single function, module, or subsystem. A + test suite may also be recursively composed by smaller test + suites.</dd> +</dl> + +== Getting started == +<ul> + <li>{@section Including the EUnit header file}</li> + <li>{@section Writing simple test functions}</li> + <li>{@section Running EUnit}</li> + <li>{@section Writing test generating functions}</li> + <li>{@section An example}</li> + <li>{@section Disabling testing}</li> + <li>{@section Avoiding compile-time dependency on EUnit}</li> +</ul> + +=== Including the EUnit header file === + +The simplest way to use EUnit in an Erlang module is to add the +following line at the beginning of the module (after the `-module' +declaration, but before any function definitions): +```-include_lib("eunit/include/eunit.hrl").''' + +This will have the following effect: +<ul> + <li>Creates an exported function `test()' (unless testing is turned + off, and the module does not already contain a test() function), that + can be used to run all the unit tests defined in the module</li> + <li>Causes all functions whose names match `..._test()' or `..._test_()' + to be automatically exported from the module (unless testing is + turned off, or the `EUNIT_NOAUTO' macro is defined)</li> + <li>Makes all the preprocessor macros of EUnit available, to help + writing tests</li> +</ul> + +<strong>Note:</strong> For `-include_lib(...)' to work, the Erlang +module search path <em>must</em> contain a directory whose name ends in +`eunit/ebin' (pointing to the `ebin' subdirectory of the EUnit +installation directory). If EUnit is installed as `lib/eunit' under your +Erlang/OTP system directory, its `ebin' subdirectory will be +automatically added to the search path when Erlang starts. Otherwise, +you need to add the directory explicitly, by passing a `-pa' flag to the +`erl' or `erlc' command. For example, a Makefile could contain the +following action for compiling `.erl' files: +```erlc -pa "path/to/eunit/ebin" $(ERL_COMPILE_FLAGS) -o$(EBIN) $<''' +or if you want Eunit to always be available when you run Erlang +interactively, you can add a line like the following to your +`$HOME/.erlang' file: +```code:add_path("/path/to/eunit/ebin").''' + +=== Writing simple test functions === + +The EUnit framework makes it extremely easy to write unit tests in +Erlang. There are a few different ways of writing them, though, so we +start with the simplest: + +A function with a name ending in `..._test()' is recognized by EUnit as +a simple test function - it takes no arguments, and its execution either +succeeds (returning some arbitrary value that EUnit will throw away), or +fails by throwing an exception of some kind (or by not terminating, in +which case it will be aborted after a while). + +An example of a simple test function could be the following: +```reverse_test() -> lists:reverse([1,2,3]).''' +This just tests that the function `lists:reverse(List)' does not crash +when `List' is `[1,2,3]'. It is not a great test, but many people write +simple functions like this one to test the basic functionality of their +code, and those tests can be used directly by EUnit, without changes, +as long as their function names match. + +==== Use exceptions to signal failure ==== + +To write more interesting tests, we need to make them crash (throw an +exception) when they don't get the result they expect. A simple way of +doing this is to use pattern matching with `=', as in the following +examples: +```reverse_nil_test() -> [] = lists:reverse([]). + reverse_one_test() -> [1] = lists:reverse([1]). + reverse_two_test() -> [2,1] = lists:reverse([1,2]). +''' +If there was some bug in `lists:reverse/1' that made it return something +other than `[2,1]' when it got `[1,2]' as input, then the last test +above would throw a `badmatch' error. The first two (we assume they do +not get a `badmatch') would simply return `[]' and `[1]', respectively, +so both succeed. (Note that EUnit is not psychic: if you write a test +that returns a value, even if it is the wrong value, EUnit will consider +it a success. You must make sure that the test is written so that it +causes a crash if the result is not what it should be.) + +==== Using assert macros ==== + +If you want to use Boolean operators for your tests, the `assert' +macro comes in handy (see {@section EUnit macros} for details): +```length_test() -> ?assert(length([1,2,3]) =:= 3).''' +The `?assert(Expression)' macro will evaluate `Expression', and if that +does not evaluate to `true', it will throw an exception; otherwise it +just returns `ok'. In the above example, the test will thus fail if the +call to `length' does not return 3. + +=== Running EUnit === + +If you have added the declaration +`-include_lib("eunit/include/eunit.hrl")' to your module, as described +above, you only need to compile the module, and run the automatically +exported function `test()'. For example, if your module was named `m', +then calling `m:test()' will run EUnit on all the tests defined in the +module. You do not need to write `-export' declarations for the test +functions. This is all done by magic. + +You can also use the function {@link eunit:test/1} to run arbitrary +tests, for example to try out some more advanced test descriptors (see +{@section EUnit test representation}). For example, running +``eunit:test(m)'' does the same thing as the auto-generated function +``m:test()'', while ``eunit:test({inparallel, m})'' runs the same test +cases but executes them all in parallel. + +==== Putting tests in separate modules ==== + +If you want to separate your test code from your normal code (at least +for testing the exported functions), you can simply write the test +functions in a module named `m_tests' (note: not `m_test'), if your +module is named `m'. Then, whenever you ask EUnit to test the module +`m', it will also look for the module `m_tests' and run those tests as +well. See `ModuleName' in the section {@section Primitives} for details. + +==== EUnit captures standard output ==== + +If your test code writes to the standard output, you may be surprised to +see that the text does not appear on the console when the tests are +running. This is because EUnit captures all standard output from test +functions (this also includes setup and cleanup functions, but not +generator functions), so that it can be included in the test report if +errors occur. To bypass EUnit and print text directly to the console +while testing, you can write to the `user' output stream, as in +`io:format(user, "~w", [Term])'. The recommended way of doing this is to +use the EUnit {@section Debugging macros}, which make it much simpler. + +=== Writing test generating functions === + +A drawback of simple test functions is that you must write a separate +function (with a separate name) for each test case. A more compact way +of writing tests (and much more flexible, as we shall see), is to write +functions that <em>return</em> tests, instead of <em>being</em> tests. + +A function with a name ending in `..._test_()' (note the final +underscore) is recognized by EUnit as a <em>test generator</em> +function. Test generators return a <em>representation</em> of a <em>set +of tests</em> to be executed by EUnit. + +==== Representing a test as data ==== + +The most basic representation of a test is a single fun-expression that +takes no arguments. For example, the following test generator: +```basic_test_() -> + fun () -> ?assert(1 + 1 =:= 2) end.''' +will have the same effect as the following simple test: +```simple_test() -> + ?assert(1 + 1 =:= 2).''' +(in fact, EUnit will handle all simple tests just like it handles +fun-expressions: it will put them in a list, and run them one by one). + +==== Using macros to write tests ==== + +To make tests more compact and readable, as well as automatically add +information about the line number in the source code where a test +occurred (and reduce the number of characters you have to type), you can +use the `_test' macro (note the initial underscore character), like +this: +```basic_test_() -> + ?_test(?assert(1 + 1 =:= 2)).''' +The `_test' macro takes any expression (the "body") as argument, and +places it within a fun-expression (along with some extra information). +The body can be any kind of test expression, just like the body of a +simple test function. + +==== Underscore-prefixed macros create test objects ==== + +But this example can be made even shorter! Most test macros, such as the +family of `assert' macros, have a corresponding form with an initial +underscore character, which automatically adds a `?_test(...)' wrapper. +The above example can then simply be written: +```basic_test_() -> + ?_assert(1 + 1 =:= 2).''' +which has exactly the same meaning (note the `_assert' instead of +`assert'). You can think of the initial underscore as signalling +<em>test object</em>. + +=== An example === + +Sometimes, an example says more than a thousand words. The following +small Erlang module shows how EUnit can be used in practice. +```-module(fib). + -export([fib/1]). + -include_lib("eunit/include/eunit.hrl"). + + fib(0) -> 1; + fib(1) -> 1; + fib(N) when N > 1 -> fib(N-1) + fib(N-2). + + fib_test_() -> + [?_assert(fib(0) =:= 1), + ?_assert(fib(1) =:= 1), + ?_assert(fib(2) =:= 2), + ?_assert(fib(3) =:= 3), + ?_assert(fib(4) =:= 5), + ?_assert(fib(5) =:= 8), + ?_assertException(error, function_clause, fib(-1)), + ?_assert(fib(31) =:= 2178309) + ].''' + +(Author's note: When I first wrote this example, I happened to write a +`*' instead of `+' in the `fib' function. Of course, this showed up +immediately when I ran the tests.) + +See {@section EUnit test representation} for a full list of all the ways +you can specify test sets in EUnit. + +=== Disabling testing === + +Testing can be turned off by defining the `NOTEST' macro when compiling, +for example as an option to `erlc', as in: +```erlc -DNOTEST my_module.erl''' +or by adding a macro definition to the code, <em>before the EUnit header +file is included</em>: +```-define(NOTEST, 1).''' +(the value is not important, but should typically be 1 or `true'). +Note that unless the `EUNIT_NOAUTO' macro is defined, disabling testing +will also automatically strip all test functions from the code, except +for any that are explicitly declared as exported. + +For instance, to use EUnit in your application, but with testing turned +off by default, put the following lines in a header file: +```-define(NOTEST, true). + -include_lib("eunit/include/eunit.hrl").''' +and then make sure that every module of your application includes that +header file. This means that you have a only a single place to modify in +order to change the default setting for testing. To override the `NOTEST' +setting without modifying the code, you can define `TEST' in a compiler +option, like this: +```erlc -DTEST my_module.erl''' + +See {@section Compilation control macros} for details about these +macros. + +=== Avoiding compile-time dependency on EUnit === + +If you are distributing the source code for your application for other +people to compile and run, you probably want to ensure that the code +compiles even if EUnit is not available. Like the example in the +previous section, you can put the following lines in a common header +file: +```-ifdef(TEST). + -include_lib("eunit/include/eunit.hrl"). + -endif.''' +and, of course, also make sure that you place all test code that uses +EUnit macros within `-ifdef(TEST)' or `-ifdef(EUNIT)' sections. + + +== EUnit macros == + +Although all the functionality of EUnit is available even without the +use of preprocessor macros, the EUnit header file defines a number of +such macros in order to make it as easy as possible to write unit tests +as compactly as possible and without getting too many details in the +way. + +Except where explicitly stated, using EUnit macros will never introduce +run-time dependencies on the EUnit library code, regardless of whether +your code is compiled with testing enabled or disabled. + +<ul> +<li>{@section Basic macros}</li> +<li>{@section Compilation control macros}</li> +<li>{@section Utility macros}</li> +<li>{@section Assert macros}</li> +<li>{@section Macros for running external commands}</li> +<li>{@section Debugging macros}</li> +</ul> + +=== Basic macros === + +<dl> +<dt>`_test(Expr)'</dt> +<dd>Turns `Expr' into a "test object", by wrapping it in a +fun-expression and a source line number. Technically, this is the same +as `{?LINE, fun () -> (Expr) end}'. +</dd> +</dl> + +=== Compilation control macros === + +<dl> +<dt>`EUNIT'</dt> +<dd>This macro is always defined to `true' whenever EUnit is enabled at +compile time. This is typically used to place testing code within +conditional compilation, as in: +```-ifdef(EUNIT). + % test code here + ... + -endif.''' +e.g., to ensure that the code can be compiled without including the +EUnit header file, when testing is disabled. See also the macros `TEST' +and `NOTEST'. +</dd> + +<dt>`EUNIT_NOAUTO'</dt> +<dd>If this macro is defined, the automatic exporting or stripping of +test functions will be disabled. +</dd> + +<dt>`TEST'</dt> +<dd>This macro is always defined (to `true', unless previously defined +by the user to have another value) whenever EUnit is enabled at compile +time. This can be used to place testing code within conditional +compilation; see also the macros `NOTEST' and `EUNIT'. + +For testing code that is strictly dependent on EUnit, it may be +preferable to use the `EUNIT' macro for this purpose, while for code +that uses more generic testing conventions, using the `TEST' macro may +be preferred. + +The `TEST' macro can also be used to override the `NOTEST' macro. If +`TEST' is defined <em>before</em> the EUnit header file is +included (even if `NOTEST' is also defined), then the code will be +compiled with EUnit enabled. +</dd> + +<dt>`NOTEST'</dt> +<dd>This macro is always defined (to `true', unless previously defined +by the user to have another value) whenever EUnit is <em>disabled</em> +at compile time. (Compare the `TEST' macro.) + +This macro can also be used for conditional compilation, but is more +typically used to disable testing: If `NOTEST' is defined +<em>before</em> the EUnit header file is included, and `TEST' +is <em>not</em> defined, then the code will be compiled with EUnit +disabled. See also {@section Disabling testing}. +</dd> + +<dt>`NOASSERT'</dt> +<dd>If this macro is defined, the assert macros will have no effect, +when testing is also disabled. See {@section Assert macros}. When +testing is enabled, the assert macros are always enabled automatically +and cannot be disabled. +</dd> + +<dt>`ASSERT'</dt> +<dd>If this macro is defined, it overrides the NOASSERT macro, forcing +the assert macros to always be enabled regardless of other settings. +</dd> + +<dt>`NODEBUG'</dt> +<dd>If this macro is defined, the debugging macros will have no effect. +See {@section Debugging macros}. `NODEBUG' also implies `NOASSERT', +unless testing is enabled. +</dd> + +<dt>`DEBUG'</dt> +<dd>If this macro is defined, it overrides the NODEBUG macro, forcing +the debugging macros to be enabled. +</dd> +</dl> + +=== Utility macros === + +The following macros can make tests more compact and readable: + +<dl> +<dt>`LET(Var,Arg,Expr)'</dt> +<dd>Creates a local binding `Var = Arg' in `Expr'. (This is the same as +`(fun(Var)->(Expr)end)(Arg)'.) Note that the binding is not exported +outside of `Expr', and that within `Expr', this binding of `Var' will +shadow any binding of `Var' in the surrounding scope. +</dd> +<dt>`IF(Cond,TrueCase,FalseCase)'</dt> +<dd>Evaluates `TrueCase' if `Cond' evaluates to `true', or otherwise +evaluates `FalseCase' if `Cond' evaluates to `false'. (This is the same +as `(case (Cond) of true->(TrueCase); false->(FalseCase) end)'.) Note +that it is an error if `Cond' does not yield a boolean value. +</dd> +</dl> + +=== Assert macros === + +(Note that these macros also have corresponding forms which start with +an "`_'" (underscore) character, as in `?_assert(BoolExpr)', that create +a "test object" instead of performing the test immediately. This is +equivalent to writing `?_test(assert(BoolExpr))', etc.) + +If the macro `NOASSERT' is defined before the EUnit header file is +included, these macros have no effect when testing is also disabled; see +{@section Compilation control macros} for details. + +<dl> +<dt>`assert(BoolExpr)'</dt> +<dd>Evaluates the expression `BoolExpr', if testing is enabled. Unless +the result is `true', an informative exception will be generated. If +there is no exception, the result of the macro expression is the atom +`ok', and the value of `BoolExpr' is discarded. If testing is disabled, +the macro will not generate any code except the atom `ok', and +`BoolExpr' will not be evaluated. + +Typical usage: +```?assert(f(X, Y) =:= [])''' + +The `assert' macro can be used anywhere in a program, not just in unit +tests, to check pre/postconditions and invariants. For example: +```some_recursive_function(X, Y, Z) -> + ?assert(X + Y > Z), + ...''' +</dd> +<dt>`assertNot(BoolExpr)'</dt> +<dd>Equivalent to `assert(not (BoolExpr))'. +</dd> +<dt>`assertMatch(GuardedPattern, Expr)'</dt> +<dd>Evaluates `Expr' and matches the result against `GuardedPattern', if +testing is enabled. If the match fails, an informative exception will be +generated; see the `assert' macro for further details. `GuardedPattern' +can be anything that you can write on the left hand side of the `->' +symbol in a case-clause, except that it cannot contain comma-separated +guard tests. + +The main reason for using `assertMatch' also for simple matches, instead +of matching with `=', is that it produces more detailed error messages. + +Examples: +```?assertMatch({found, {fred, _}}, lookup(bloggs, Table))''' +```?assertMatch([X|_] when X > 0, binary_to_list(B))''' +</dd> +<dt>`assertEqual(Expect, Expr)'</dt> +<dd>Evaluates the expressions `Expect' and `Expr' and compares the +results for equality, if testing is enabled. If the values are not +equal, an informative exception will be generated; see the `assert' +macro for further details. + +`assertEqual' is more suitable than than `assertMatch' when the +left-hand side is a computed value rather than a simple pattern, and +gives more details than `?assert(Expect =:= Expr)'. + +Examples: +```?assertEqual("b" ++ "a", lists:reverse("ab"))''' +```?assertEqual(foo(X), bar(Y))''' +</dd> +<dt>`assertException(ClassPattern, TermPattern, Expr)'</dt> +<dt>`assertError(TermPattern, Expr)'</dt> +<dt>`assertExit(TermPattern, Expr)'</dt> +<dt>`assertThrow(TermPattern, Expr)'</dt> +<dd>Evaluates `Expr', catching any exception and testing that it matches +the expected `ClassPattern:TermPattern'. If the match fails, or if no +exception is thrown by `Expr', an informative exception will be +generated; see the `assert' macro for further details. The +`assertError', `assertExit', and `assertThrow' macros, are equivalent to +using `assertException' with a `ClassPattern' of `error', `exit', or +`throw', respectively. + +Examples: +```?assertError(badarith, X/0)''' +```?assertExit(normal, exit(normal))''' +```?assertException(throw, {not_found,_}, throw({not_found,42}))''' +</dd> +</dl> + +=== Macros for running external commands === + +Keep in mind that external commands are highly dependent on the +operating system. You can use the standard library function `os:type()' +in test generator functions, to produce different sets of tests +depending on the current operating system. + +Note: these macros introduce a run-time dependency on the EUnit library +code, if compiled with testing enabled. + +<dl> +<dt>`assertCmd(CommandString)'</dt> +<dd>Runs `CommandString' as an external command, if testing is enabled. +Unless the returned status value is 0, an informative exception will be +generated. If there is no exception, the result of the macro expression +is the atom `ok'. If testing is disabled, the macro will not generate +any code except the atom `ok', and the command will not be executed. + +Typical usage: +```?assertCmd("mkdir foo")''' +</dd> +<dt>`assertCmdStatus(N, CommandString)'</dt> +<dd>Like the `assertCmd(CommandString)' macro, but generates an +exception unless the returned status value is `N'. +</dd> +<dt>`assertCmdOutput(Text, CommandString)'</dt> +<dd>Runs `CommandString' as an external command, if testing is enabled. +Unless the output produced by the command exactly matches the specified +string `Text', an informative exception will be generated. (Note that +the output is normalized to use a single LF character as line break on +all platforms.) If there is no exception, the result of the macro +expression is the atom `ok'. If testing is disabled, the macro will not +generate any code except the atom `ok', and the command will not be +executed. +</dd> +<dt>`cmd(CommandString)'</dt> +<dd>Runs `CommandString' as an external command. Unless the returned +status value is 0 (indicating success), an informative exception will be +generated; otherwise, the result of the macro expression is the output +produced by the command, as a flat string. The output is normalized to +use a single LF character as line break on all platforms. + +This macro is useful in the setup and cleanup sections of fixtures, +e.g., for creating and deleting files or perform similar operating +system specific tasks, to make sure that the test system is informed of +any failures. + +A Unix-specific example: +```{setup, + fun () -> ?cmd("mktemp") end, + fun (FileName) -> ?cmd("rm " ++ FileName) end, + ...}''' +</dd> +</dl> + +=== Debugging macros === + +To help with debugging, EUnit defines several useful macros for printing +messages directly to the console (rather than to the standard output). +Furthermore, these macros all use the same basic format, which includes +the file and line number where they occur, making it possible in some +development environments (e.g., when running Erlang in an Emacs buffer) +to simply click on the message and jump directly to the corresponding +line in the code. + +If the macro `NODEBUG' is defined before the EUnit header file is +included, these macros have no effect; see +{@section Compilation control macros} for details. + +<dl> +<dt>`debugHere'</dt> +<dd>Just prints a marker showing the current file and line number. Note +that this is an argument-less macro. The result is always `ok'.</dd> +<dt>`debugMsg(Text)'</dt> +<dd>Outputs the message `Text' (which can be a plain string, an IO-list, +or just an atom). The result is always `ok'.</dd> +<dt>`debugFmt(FmtString, Args)'</dt> +<dd>This formats the text like `io:format(FmtString, Args)' and outputs +it like `debugMsg'. The result is always `ok'.</dd> +<dt>`debugVal(Expr)'</dt> +<dd>Prints both the source code for `Expr' and its current value. E.g., +`?debugVal(f(X))' might be displayed as "`f(X) = 42'". (Large terms are +shown truncated.) The result is always the value of `Expr', so this +macro can be wrapped around any expression to display its value when +the code is compiled with debugging enabled.</dd> +<dt>`debugTime(Text,Expr)'</dt> +<dd>Prints `Text' and the wall clock time for evaluation of `Expr'. The +result is always the value of `Expr', so this macro can be wrapped +around any expression to show its run time when the code is compiled +with debugging enabled. For example, `List1 = ?debugTime("sorting", +lists:sort(List))' might show as "`sorting: 0.015 s'".</dd> + +</dl> + + +== EUnit test representation == + +The way EUnit represents tests and test sets as data is flexible, +powerful, and concise. This section describes the representation in +detail. + +<ul> +<li>{@section Simple test objects}</li> +<li>{@section Test sets and deep lists}</li> +<li>{@section Titles}</li> +<li>{@section Primitives}</li> +<li>{@section Control}</li> +<li>{@section Fixtures}</li> +<li>{@section Lazy generators}</li> +</ul> + +=== Simple test objects === + +A <em>simple test object</em> is one of the following: +<ul> + <li>A nullary functional value (i.e., a fun that takes zero + arguments). Examples: +```fun () -> ... end''' +```fun some_function/0''' +```fun some_module:some_function/0''' + </li> + <li>A pair of atoms `{ModuleName, FunctionName}', referring to the + function `ModuleName:FunctionName/0'</li> + <li>A pair `{LineNumber, SimpleTest}', where `LineNumber' is a + nonnegative integer and `SimpleTest' is another simple test + object. `LineNumber' should indicate the source line of the test. + Pairs like this are usually only created via `?_test(...)' macros; + see {@section Basic macros}.</li> +</ul> +In brief, a simple test object consists of a single function that takes +no arguments (possibly annotated with some additional metadata, i.e., a +line number). Evaluation of the function either <em>succeeds</em>, by +returning some value (which is ignored), or <em>fails</em>, by throwing +an exception. + +=== Test sets and deep lists === + +A test set can be easily created by placing a sequence of test objects +in a list. If `T_1', ..., `T_N' are individual test objects, then `[T_1, +..., T_N]' is a test set consisting of those objects (in that order). + +Test sets can be joined in the same way: if `S_1', ..., `S_K' are test +sets, then `[S_1, ..., S_K]' is also a test set, where the tests of +`S_i' are ordered before those of `S_(i+1)', for each subset `S_i'. + +Thus, the main representation of test sets is <em>deep lists</em>, and +a simple test object can be viewed as a test set containing only a +single test; there is no difference between `T' and `[T]'. + +A module can also be used to represent a test set; see `ModuleName' +under {@section Primitives} below. + +=== Titles === + +Any test or test set `T' can be annotated with a title, by wrapping it +in a pair `{Title, T}', where `Title' is a string. For convenience, any +test which is normally represented using a tuple can simply be given a +title string as the first element, i.e., writing `{"The Title", ...}' +instead of adding an extra tuple wrapper as in `{"The Title", {...}}'. + + +=== Primitives === + +The following are primitives, which do not contain other test sets as +arguments: +<dl> +<dt>`ModuleName::atom()' +</dt> +<dd>A single atom represents a module name, and is equivalent to +`{module, ModuleName}'. This is often used as in the call +`eunit:test(some_module)'. +</dd> +<dt>`{module, ModuleName::atom()}' +</dt> +<dd>This composes a test set from the exported test functions of the +named module, i.e., those functions with arity zero whose names end +with `_test' or `_test_'. Basically, the `..._test()' functions become +simple tests, while the `..._test_()' functions become generators. + +In addition, EUnit will also look for another module whose name is +`ModuleName' plus the suffix `_tests', and if it exists, all the tests +from that module will also be added. (If `ModuleName' already contains +the suffix `_tests', this is not done.) E.g., the specification +`{module, mymodule}' will run all tests in the modules `mymodule' and +`mymodule_tests'. Typically, the `_tests' module should only contain +test cases that use the public interface of the main module (and no +other code). +</dd> +<dt>`{application, AppName::atom(), Info::list()}' +</dt> +<dd>This is a normal Erlang/OTP application descriptor, as found in an + `.app' file. The resulting test set consists of the modules listed in + the `modules' entry in `Info'. +</dd> +<dt>`{application, AppName::atom()}' +</dt> +<dd>This creates a test set from all the modules belonging to the +specified application, by consulting the application's `.app' file +(see `{file, FileName}'), or if no such file exists, by testing all +object files in the application's <tt>ebin</tt>-directory (see `{dir, +Path}'); if that does not exist, the `code:lib_dir(AppName)' directory +is used. +</dd> +<dt>`Path::string()' +</dt> +<dd>A single string represents the path of a file or directory, and is +equivalent to `{file, Path}', or `{dir, Path}', respectively, depending +on what `Path' refers to in the file system. +</dd> +<dt>`{file, FileName::string()}' +</dt> +<dd>If `FileName' has a suffix that indicates an object file (`.beam'), +EUnit will try to reload the module from the specified file and test it. +Otherwise, the file is assumed to be a text file containing test +specifications, which will be read using the standard library function +`file:path_consult/2'. + +Unless the file name is absolute, the file is first searched for +relative to the current directory, and then using the normal search path +(`code:get_path()'). This means that the names of typical "app" files +can be used directly, without a path, e.g., `"mnesia.app"'. +</dd> +<dt>`{dir, Path::string()}' +</dt> +<dd>This tests all object files in the specified directory, as if they +had been individually specified using `{file, FileName}'. +</dd> +<dt>`{generator, GenFun::(() -> Tests)}' +</dt> +<dd>The generator function `GenFun' is called to produce a test +set. +</dd> +<dt>`{generator, ModuleName::atom(), FunctionName::atom()}' +</dt> +<dd>The function `ModuleName:FunctionName()' is called to produce a test +set. +</dd> +<dt>`{with, X::any(), [AbstractTestFun::((any()) -> any())]}' +</dt> +<dd>Distributes the value `X' over the unary functions in the list, +turning them into nullary test functions. An `AbstractTestFun' is like +an ordinary test fun, but takes one argument instead of zero - it's +basically missing some information before it can be a proper test. In +practice, `{with, X, [F_1, ..., F_N]}' is equivalent to `[fun () -> +F_1(X) end, ..., fun () -> F_N(X) end]'. This is particularly useful if +your abstract test functions are already implemented as proper +functions: `{with, FD, [fun filetest_a/1, fun filetest_b/1, fun +filetest_c/1]}' is equivalent to `[fun () -> filetest_a(FD) end, fun () +-> filetest_b(FD) end, fun () -> filetest_c(FD) end]', but much more +compact. See also {@section Fixtures}, below. +</dd> +</dl> + +=== Control === + +The following representations control how and where tests are executed: +<dl> +<dt>`{spawn, Tests}'</dt> +<dd>Runs the specified tests in a separate subprocess, while the current +test process waits for it to finish. This is useful for tests that need +a fresh, isolated process state. (Note that EUnit always starts at least +one such a subprocess automatically; tests are never executed by the +caller's own process.)</dd> +<dt>`{spawn, Node::atom(), Tests}'</dt> +<dd>Like `{spawn, Tests}', but runs the specified tests on the given +Erlang node.</dd> +<dt>`{timeout, Time::number(), Tests}'</dt> +<dd>Runs the specified tests under the given timeout. Time is in +seconds; e.g., 60 means one minute and 0.1 means 1/10th of a second. If +the timeout is exceeded, the unfinished tests will be forced to +terminate. Note that if a timeout is set around a fixture, it includes +the time for setup and cleanup, and if the timeout is triggered, the +entire fixture is abruptly terminated (without running the +cleanup).</dd> +<dt>`{inorder, Tests}'</dt> +<dd>Runs the specified tests in strict order. Also see `{inparallel, +Tests}'. By default, tests are neither marked as `inorder' or +`inparallel', but may be executed as the test framework chooses.</dd> +<dt>`{inparallel, Tests}'</dt> +<dd>Runs the specified tests in parallel (if possible). Also see +`{inorder, Tests}'.</dd> +<dt>`{inparallel, N::integer(), Tests}'</dt> +<dd>Like `{inparallel, Tests}', but running no more than `N' subtests +simultaneously.</dd> +</dl> + +=== Fixtures === + +A "fixture" is some state that is necessary for a particular set of +tests to run. EUnit's support for fixtures makes it easy to set up such +state locally for a test set, and automatically tear it down again when +the test set is finished, regardless of the outcome (success, failures, +timeouts, etc.). + +To make the descriptions simpler, we first list some definitions: +<center> +<table border="0" cellspacing="4"> +<tr> +<td>`Setup'</td><td>`() -> (R::any())'</td> +</tr> +<tr> +<td>`SetupX'</td><td>`(X::any()) -> (R::any())'</td> +</tr> +<tr> +<td>`Cleanup'</td><td>`(R::any()) -> any()'</td> +</tr> +<tr> +<td>`CleanupX'</td><td>`(X::any(), R::any()) -> any()'</td> +</tr> +<tr> +<td>`Instantiator'</td><td>`((R::any()) -> Tests) | {with, [AbstractTestFun::((any()) -> any())]}'</td> +</tr> +<tr> +<td>`Where'</td><td>`local | spawn | {spawn, Node::atom()}'</td> +</tr> +</table> +</center> +(these are explained in more detail further below.) + +The following representations specify fixture handling for test sets: +<dl> +<dt>`{setup, Setup, Tests | Instantiator}'</dt> +<dt>`{setup, Setup, Cleanup, Tests | Instantiator}'</dt> +<dt>`{setup, Where, Setup, Tests | Instantiator}'</dt> +<dt>`{setup, Where, Setup, Cleanup, Tests | Instantiator}'</dt> +<dd>`setup' sets up a single fixture for running all of the specified +tests, with optional teardown afterwards. The arguments are described in +detail below. +</dd> +<dt>`{node, Node::atom(), Tests | Instantiator}'</dt> +<dt>`{node, Node::atom(), Args::string(), Tests | Instantiator}'</dt> +<dd>`node' is like `setup', but with a built-in behaviour: it starts a +slave node for the duration of the tests. The atom `Node' should have +the format `[email protected]', and `Args' are the optional +arguments to the new node; see `slave:start_link/3' for details. +</dd> +<dt>`{foreach, Where, Setup, Cleanup, [Tests | Instantiator]}'</dt> +<dt>`{foreach, Setup, Cleanup, [Tests | Instantiator]}'</dt> +<dt>`{foreach, Where, Setup, [Tests | Instantiator]}'</dt> +<dt>`{foreach, Setup, [Tests | Instantiator]}'</dt> +<dd>`foreach' is used to set up a fixture and optionally tear it down +afterwards, repeated for each single one of the specified test sets. +</dd> +<dt>`{foreachx, Where, SetupX, CleanupX, + Pairs::[{X::any(), ((X::any(), R::any()) -> Tests)}]}'</dt> +<dt>`{foreachx, SetupX, CleanupX, Pairs}'</dt> +<dt>`{foreachx, Where, SetupX, Pairs}'</dt> +<dt>`{foreachx, SetupX, Pairs}'</dt> +<dd>`foreachx' is like `foreach', but uses a list of pairs, each +containing an extra argument `X' and an extended instantiator function. +</dd> +</dl> + +A `Setup' function is executed just before any of the specified tests +are run, and a `Cleanup' function is executed when no more of the +specified tests will be run, regardless of the reason. A `Setup' +function takes no argument, and returns some value which will be passed +as it is to the `Cleanup' function. A `Cleanup' function should do +whatever necessary and return some arbitrary value, such as the atom +`ok'. (`SetupX' and `CleanupX' functions are similar, but receive one +additional argument: some value `X', which depends on the context.) When +no `Cleanup' function is specified, a dummy function is used which has +no effect. + +An `Instantiator' function receives the same value as the `Cleanup' +function, i.e., the value returned by the `Setup' function. It should +then behave much like a generator (see {@section Primitives}), and +return a test set whose tests have been <em>instantiated</em> with the +given value. A special case is the syntax `{with, [AbstractTestFun]}' +which represents an instantiator function that distributes the value +over a list of unary functions; see {@section Primitives}: `{with, X, +[...]}' for more details. + +A `Where' term controls how the specified tests are executed. The +default is `spawn', which means that the current process handles the +setup and teardown, while the tests are executed in a subprocess. +`{spawn, Node}' is like `spawn', but runs the subprocess on the +specified node. `local' means that the current process will handle both +setup/teardown and running the tests - the drawback is that if a test +times out so that the process is killed, the <em>cleanup will not be +performed</em>; hence, avoid this for persistent fixtures such as file +operations. In general, 'local' should only be used when: +<ul> + <li>the setup/teardown needs to be executed by the process that will + run the tests;</li> + <li>no further teardown needs to be done if the process is killed + (i.e., no state outside the process was affected by the setup)</li> +</ul> + +=== Lazy generators === + +Sometimes, it can be convenient not to produce the whole set of test +descriptions before the testing begins; for example, if you want to +generate a huge amount of tests that would take up too much space to +keep in memory all at once. + +It is fairly easy to write a generator which, each time it is called, +either produces an empty list if it is done, or otherwise produces a +list containing a single test case plus a new generator which will +produce the rest of the tests. This demonstrates the basic pattern: + +```lazy_test_() -> + lazy_gen(10000). + + lazy_gen(N) -> + {generator, + fun () -> + if N > 0 -> + [?_test(...) + | lazy_gen(N-1)]; + true -> + [] + end + end}.''' + +When EUnit traverses the test representation in order to run the tests, +the new generator will not be called to produce the next test until the +previous test has been executed. + +Note that it is easiest to write this kind of recursive generator using +a help function, like the `lazy_gen/1' function above. It can also be +written using a recursive fun, if you prefer to not clutter your +function namespace and are comfortable with writing that kind of code. |