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<title> Testing Dancer with Test::Mojo | PerlDancer Advent Calendar</title>
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<a href="/" class="homelink">Dancer Advent Calendar</a><br />
<p>
The PerlDancer Advent Calendar is a community-driven project that aims
to showcase the Dancer Perl web framework.
</p>
<p>
Each day of December until Christmas, one article about Dancer. Stay tuned for new moves!
</p>
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<h3>About Dancer</h3>
<ul class="links">
<li><a href="http://www.perldancer.org/">Dancer homepage</a></li>
<li><a href="http://twitter.com/PerlDancer">Official Twitter</a></li>
<li><a href="http://github.com/PerlDancer/Dancer">Dancer on GitHub</a></li>
<li><a href="http://github.com/PerlDancer/Dancer2">Dancer 2 on GitHub</a></li>
<li><a class="feed" href="/feed/2018">RSS</a></li>
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<div class="pod-document"><h1><a name="testing_dancer_with_test__mojo"></a>Testing Dancer with Test::Mojo</h1>
<p>Authors of Dancer (and other) PSGI applications are probably accustomed to <a href="https://metacpan.org/pod/distribution/Dancer2/lib/Dancer2/Manual.pod#TESTING">testing</a> with <a href="https://metacpan.org/pod/Plack::Test">Plack::Test</a>, and ...
<p>During advent last year, I wrote about <a href="https://mojolicious.org/perldoc/Test/Mojo">Test::Mojo</a>, showing the many easy and (dare I say) fun ways that you can use it to test your Mojolicious applications.
If you missed it, go <a href="https://mojolicious.io/blog/2017/12/09/day-9-the-best-way-to-test/">check it out</a>.</p>
<p>I expect there are at least a few of you out there who read that and think, "I'd love to use that, but I don't use Mojolicious!"; well, you're in luck!
With just a little role to bridge the gap, you can use Test::Mojo to test your PSGI applications too!</p>
<h2><a name="mounting_psgi_applications"></a>Mounting PSGI Applications</h2>
<p>Mojolicious itself doesn't use the <a href="https://metacpan.org/pod/PSGI">PSGI</a> protocol, owing to certain features that it doesn't provide and which are necessary for certain asynchronous operations.
That said, you can serve a Mojolicious application on a PSGI server by using <a href="https://mojolicious.org/perldoc/Mojo/Server/PSGI">Mojo::Server::PSGI</a>.
This Mojolicious-core module is automatically used for you when your Mojolicious-based app detects that it has started under a PSGI server (e.g. plackup or Starman).</p>
<p>While translating between a Mojo app and a PSGI server is core functionality, doing the opposite, translating between a PSGI app and a Mojolicious server (or app, as you'll see) is available as a third party module.
<a href="https://metacpan.org/pod/Mojolicious::Plugin::MountPSGI">Mojolicious::Plugin::MountPSGI</a>, as it's name implies, can mount a PSGI application into a Mojolicious-based one.
To do so, it builds a new, empty Mojolicious application that translates all requests to PSGI environments before dispatching to it as with any <a href="https://mojolicious.org/perldoc/Mojolicious/Plugin/Mount">mount</a>-ed application.</p>
<h2><a name="testing_using_test__mojo"></a>Testing using Test::Mojo</h2>
<p>Once you can do that, it is trivial to take a PSGI application, wrap it with MountPSGI, and set it as the application for use with Test::Mojo.
Still, to make it even easier, that has all been done for you in <a href="https://metacpan.org/pod/Test::Mojo::Role::PSGI">Test::Mojo::Role::PSGI</a>.</p>
<p>Like any <a href="https://mojolicious.io/blog/2017/12/13/day-13-more-about-roles/">Mojolicious Role</a>, we can use <code>with_roles</code> to create a (mostly anonymous) subclass with the role applied.
You can use the shortcut <code>+</code> to stand in for <code>Test::Mojo::Role::</code>.</p>
<pre class="prettyprint">use Test::Mojo;
my $class = Test::Mojo->with_roles('+PSGI');</pre>
<p>Then you instantiate that role with the path to the PSGI application, or else the PSGI application itself.</p>
<p>Since you're using roles, which are all about composition, you can also apply other roles that you might <a href="https://metacpan.org/search?q=%22Test%3A%3AMojo%3A%3ARole%22">find on CPAN</a>.</p>
<h2><a name="an_example"></a>An Example</h2>
<p>As an example, let's say we have a simple application script (named <code>app.psgi</code>) that can render a <code>"hello world"</code> or <code>"hello $user"</code> in several formats.
I'll allow a plain text response, JSON, and templated HTML (using the <a href="https://metacpan.org/pod/Dancer2::Template::Simple">simple</a> template to keep this concise).</p>
<pre class="prettyprint">use Dancer2;
set template => 'simple';
set views => '.';
any '/text' => sub {
my $name = param('name') // 'world';
send_as plain => "hello $name";
};
any '/data' => sub {
my $name = param('name') // 'world';
send_as JSON => { hello => $name };
};
any '/html' => sub {
my $name = param('name') // 'world';
template 'hello' => { name => $name };
};
start;</pre>
<p>And the template (<code>hello.tt</code>) is</p>
<pre class="prettyprint"><dl id="data">
<dt id="hello">hello</dt>
<dd><% name %></dd>
</dl></pre>
<p>The <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Element/dl">dl</a>, <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Element/dt">dt</a> and <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Element/dd">dd</a> tags...
The HTML I've built, while nice for display isn't necessarily nice for querying programmatically, this is on purpose for the example.</p>
<h2><a name="the_tests"></a>The Tests</h2>
<p>Of course we could start the application with <a href="https://metacpan.org/pod/distribution/Plack/script/plackup">plackup</a> but that's not what we're trying to do.
I'll break the test script down a bit but if you want to see any of these files look at the <a href="https://github.com/MojoliciousDotIO/mojolicious.io/tree/master/blog/2018/12/20/testing-dancer/ex">blog repo</a> for a full listing.
Instead, let's load this into a test script.</p>
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