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+			-*- 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.