Plack::Test(3) Test PSGI applications with various backends


use Plack::Test;
use HTTP::Request::Common;
# Simple OO interface
my $app = sub { return [ 200, [], [ "Hello "] ] };
my $test = Plack::Test->create($app);
my $res = $test->request(GET "/");
is $res->content, "Hello";
# traditional - named params
app => sub {
my $env = shift;
return [ 200, [ 'Content-Type' => 'text/plain' ], [ "Hello World" ] ],
client => sub {
my $cb = shift;
my $req = HTTP::Request->new(GET => "http://localhost/hello");
my $res = $cb->($req);
like $res->content, qr/Hello World/;
# positional params (app, client)
my $app = sub { return [ 200, [], [ "Hello "] ] };
test_psgi $app, sub {
my $cb = shift;
my $res = $cb->(GET "/");
is $res->content, "Hello";


Plack::Test is a unified interface to test PSGI applications using HTTP::Request and HTTP::Response objects. It also allows you to run PSGI applications in various ways. The default backend is "Plack::Test::MockHTTP", but you may also use any Plack::Handler implementation to run live HTTP requests against a web server.


  $test = Plack::Test->create($app, %options);

creates an instance of Plack::Test implementation class. $app has to be a valid PSGI application code reference.

  $res = $test->request($request);

takes an HTTP::Request object, runs it through the PSGI application to test and returns an HTTP::Response object.


Plack::Test also provides a functional interface that takes two callbacks, each of which represents PSGI application and HTTP client code that tests the application.
  test_psgi $app, $client;
  test_psgi app => $app, client => $client;

Runs the client test code $client against a PSGI application $app. The client callback gets one argument $cb, a callback that accepts an "HTTP::Request" object and returns an "HTTP::Response" object.

Use HTTP::Request::Common to import shortcuts for creating requests for "GET", "POST", "DELETE", and "PUT" operations.

For your convenience, the "HTTP::Request" given to the callback automatically uses the HTTP protocol and the localhost ( by default), so the following code just works:

  use HTTP::Request::Common;
  test_psgi $app, sub {
      my $cb  = shift;
      my $res = $cb->(GET "/hello");

Note that however, it is not a good idea to pass an arbitrary (i.e. user-input) string to "GET" or even "HTTP::Request->new" by assuming that it always represents a path, because:

  my $req = GET "//foo/bar";

would represent a request for a URL that has no scheme, has a hostname foo and a path /bar, instead of a path //foo/bar which you might actually want.


Specify the Plack::Test backend using the environment variable "PLACK_TEST_IMPL" or $Plack::Test::Impl package variable.

The available values for the backend are:

(Default) Creates a PSGI env hash out of HTTP::Request object, runs the PSGI application in-process and returns HTTP::Response.
Runs one of Plack::Handler backends ("Standalone" by default) and sends live HTTP requests to test.
Runs tests against an external server specified in the "PLACK_TEST_EXTERNALSERVER_URI" environment variable instead of spawning the application in a server locally.

For instance, test your application with the "HTTP::Server::ServerSimple" server backend with:

  > env PLACK_TEST_IMPL=Server PLACK_SERVER=HTTP::Server::ServerSimple \
    prove -l t/test.t


Tatsuhiko Miyagawa