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<header>
<copyright>
<year>2012</year><year>2016</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
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</legalnotice>
<title>assert.hrl</title>
<prepared></prepared>
<docno></docno>
<date></date>
<rev></rev>
</header>
<file>assert.hrl.xml</file>
<filesummary>Assert macros.</filesummary>
<description>
<p>The include file <c>assert.hrl</c> provides macros for inserting
assertions in your program code.</p>
<p>Include the following directive in the module from which the function is
called:</p>
<code type="none">
-include_lib("stdlib/include/assert.hrl").</code>
<p>When an assertion succeeds, the assert macro yields the atom <c>ok</c>.
When an assertion fails, an exception of type <c>error</c> is generated.
The associated error term has the form <c>{Macro, Info}</c>. <c>Macro</c>
is the macro name, for example, <c>assertEqual</c>. <c>Info</c> is a list
of tagged values, such as <c>[{module, M}, {line, L}, ...]</c>, which
gives more information about the location and cause of the exception. All
entries in the <c>Info</c> list are optional; do not rely programatically
on any of them being present.</p>
<p>If the macro <c>NOASSERT</c> is defined when <c>assert.hrl</c> is read
by the compiler, the macros are defined as equivalent to the atom
<c>ok</c>. The test is not performed and there is no cost at runtime.</p>
<p>For example, using <c>erlc</c> to compile your modules, the following
disable all assertions:</p>
<code type="none">
erlc -DNOASSERT=true *.erl</code>
<p>The value of <c>NOASSERT</c> does not matter, only the fact that it is
defined.</p>
<p>A few other macros also have effect on the enabling or disabling of
assertions:</p>
<list type="bulleted">
<item><p>If <c>NODEBUG</c> is defined, it implies <c>NOASSERT</c>, unless
<c>DEBUG</c> is also defined, which is assumed to take precedence.</p>
</item>
<item><p>If <c>ASSERT</c> is defined, it overrides <c>NOASSERT</c>, that
is, the assertions remain enabled.</p></item>
</list>
<p>If you prefer, you can thus use only <c>DEBUG</c>/<c>NODEBUG</c> as the
main flags to control the behavior of the assertions (which is useful if
you have other compiler conditionals or debugging macros controlled by
those flags), or you can use <c>ASSERT</c>/<c>NOASSERT</c> to control only
the assert macros.</p>
</description>
<section>
<title>Macros</title>
<taglist>
<tag><c>assert(BoolExpr)</c></tag>
<item>
<p>Tests that <c>BoolExpr</c> completes normally returning
<c>true</c>.</p>
</item>
<tag><c>assertNot(BoolExpr)</c></tag>
<item>
<p>Tests that <c>BoolExpr</c> completes normally returning
<c>false</c>.</p>
</item>
<tag><c>assertMatch(GuardedPattern, Expr)</c></tag>
<item>
<p>Tests that <c>Expr</c> completes normally yielding a value that
matches <c>GuardedPattern</c>, for example:</p>
<code type="none">
?assertMatch({bork, _}, f())</code>
<p>Notice that a guard <c>when ...</c> can be included:</p>
<code type="none">
?assertMatch({bork, X} when X > 0, f())</code>
</item>
<tag><c>assertNotMatch(GuardedPattern, Expr)</c></tag>
<item>
<p>Tests that <c>Expr</c> completes normally yielding a value that does
not match <c>GuardedPattern</c>.</p>
<p>As in <c>assertMatch</c>, <c>GuardedPattern</c> can have a
<c>when</c> part.</p>
</item>
<tag><c>assertEqual(ExpectedValue, Expr)</c></tag>
<item>
<p>Tests that <c>Expr</c> completes normally yielding a value that is
exactly equal to <c>ExpectedValue</c>.</p>
</item>
<tag><c>assertNotEqual(ExpectedValue, Expr)</c></tag>
<item>
<p>Tests that <c>Expr</c> completes normally yielding a value that is
not exactly equal to <c>ExpectedValue</c>.</p>
</item>
<tag><c>assertException(Class, Term, Expr)</c></tag>
<item>
<p>Tests that <c>Expr</c> completes abnormally with an exception of type
<c>Class</c> and with the associated <c>Term</c>. The assertion fails
if <c>Expr</c> raises a different exception or if it completes
normally returning any value.</p>
<p>Notice that both <c>Class</c> and <c>Term</c> can be guarded
patterns, as in <c>assertMatch</c>.</p>
</item>
<tag><c>assertNotException(Class, Term, Expr)</c></tag>
<item>
<p>Tests that <c>Expr</c> does not evaluate abnormally with an
exception of type <c>Class</c> and with the associated <c>Term</c>.
The assertion succeeds if <c>Expr</c> raises a different exception or
if it completes normally returning any value.</p>
<p>As in <c>assertException</c>, both <c>Class</c> and <c>Term</c> can
be guarded patterns.</p>
</item>
<tag><c>assertError(Term, Expr)</c></tag>
<item>
<p>Equivalent to <c>assertException(error, Term, Expr)</c></p>
</item>
<tag><c>assertExit(Term, Expr)</c></tag>
<item>
<p>Equivalent to <c>assertException(exit, Term, Expr)</c></p>
</item>
<tag><c>assertThrow(Term, Expr)</c></tag>
<item>
<p>Equivalent to <c>assertException(throw, Term, Expr)</c></p>
</item>
</taglist>
</section>
<section>
<title>See Also</title>
<p><seealso marker="compiler:compile"><c>compile(3)</c></seealso>,
<seealso marker="erts:erlc"><c>erlc(3)</c></seealso></p>
</section>
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