Johan Lindström > Test-Case > Test::Case

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NAME ^

Test::Case - Declare test cases and feed the configuration data to tests

DESCRIPTION ^

Test::Case helps you separate the variant and invariant pieces of a test into data and code.

While this is not rocket science, it provides a nice structure in which to write tests along with some niceties to mitigate the downsides.

SYNOPSIS ^

    use Test::More;
    use Test::Case;

    my $cases = [
        {
            prefix      => "17+1",
            description => "Adding seventeen and one is even",
            setup       => { start => 17, add     => 1 },
            expected    => { sum   => 18, is_even => 1 },
        },
        # ... more cases
    ];
    test_each_case $cases => sub {
        my ($case, $setup, $expected) = @_;
        note "Setup";
        # This would call the unit under test
        my $result = $setup->{start} + $setup->{add};

        note "Test";
        is($result, $expected->{sum}, "+ works, awesome");
        is($result %2 == 0, $expected->{is_even}, "   and is_even is ok");
    };

Runs as

    #
    #
    # *** Adding seventeen and one is even ***
    # 17+1: Setup
    # 17+1: Test
    ok 1 - + works, awesome
    ok 2 -    and is_even is ok
    1..2

EXPORTED SUBROUTINES ^

test_each_case(@$cases, &$test_sub)

    test_each_case $cases => sub {
        my ($case, $setup, $expected) = @_;
        # Test code here
    };

Run through each $case (hash ref with keys: prefix, setup, etc. from the config) and call $test_sub with $case, $setup, and $expected.

$setup is shorthand for $case->{setup}

$expected is shorthand for $case->{expected};

If you provide a $case->{description} or $case->{prefix}, it is displayed at the start of each case. This is a very good idea.

If you provide a $case->{prefix}, it is set at the start of each case and cleared out at the end. See Test::More::Prefix. This is useful if you have a long test which needs a lot of note statements to keep the reader informed about what's going on.

PROS AND CONS ^

Why would I want to do this?

Splitting the test into variant data and the invariant source code leads to a few interesting properties.

Overview

It's easy to get an overview of which cases are tested just by looking at the case descriptions, either in the configuration or in the test output.

Clear

Keeping all test configuration in one place makes it clear what really defines a test case; what distinguishes it from the other cases.

Extensible

It's trivial to extend the configuration with a new case, making it more likely that you cover edge cases properly.

It's also easy to add test configuration for error conditions in a piecemeal way.

What's the downside?

As we're running the same code again and again, it's difficult to follow along in the test output. The only thing distinguishing one from the other is the setup data being used.

This is what makes it important to communicate which test case is being run.

test_each_case will help you with this by using the case description and prefix. But you'll also find it useful to note the name and value of important variables in the test code.

EXAMPLE ^

Here is a longer, complete, example of a dummy class and the tests for it.

    # This contrived example is a bit long, so here's a ToC
    # 1. A dummy class Squirt, to have something to test
    # 2. Test data defining test cases
    # 3. Test code using test_each_case

    use strict;
    use warnings;

    # 1. A dummy class Squirt, to have something to test
    package Squirt;
    use Moose;

    has x => (is => "ro");

    sub int_sqrt {
        my ($self) = @_;
        my $x = $self->x;
        die("Can't do sqrt on negative numbers ($x)") if($x < 0);
        return int( sqrt($x) );
    }


    package main;
    use Test::More;
    use Test::Case;

    # 2. Test data defining test cases
    my $cases = [
        {
            description => "Negative number; dies correctly",
            setup => {
                sqrt_of => -412,
            },
            expected => {
                dies_with => qr/^Can't do sqrt on negative numbers \(-412\)/,
            },
        },
        {
            description => "Normal, 0",
            setup       => { sqrt_of => 0 },
            expected    => { result => 0 },
        },
        {
            description => "Normal, 9,",
            setup       => { sqrt_of => 9 },
            expected    => { result => 3 },
        },
        {
            prefix      => "Round dn",
            description => "Normal, 9.1, rounds down correctly",
            setup       => { sqrt_of => 9.1 },
            expected    => { result => 3 },
        },
        {
            prefix      => "Round up",
            description => "Normal, 8.9, rounds up correctly",
            setup       => { sqrt_of => 8.9 },
            expected    => { result => 2 },
        },
    ];

    # 3. Test code using test_each_case
    test_each_case $cases => sub {
        my ($case, $setup, $expected) = @_;

        note "Setup";
        my $squirt = Squirt->new({ x => $setup->{sqrt_of} });

        note "Test";
        my $result = eval { $squirt->int_sqrt() };
        if(my $e = $@) {
            if(my $expected_dies_with = $expected->{dies_with}) {
                like($e, $expected_dies_with, "Dies ok ($expected_dies_with)");
            }
            else {
                fail("Didn't expect to die with ($e)");
            }
            return;
        }

        like($result, qr/^\d+$/, "Result contains only digits");
        is($result, $expected->{result}, "Correct result ($expected->{result})");
    };

    done_testing;

BUGS ^

Please report any bugs or feature requests to bug-test-case at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Test-Case. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT ^

You can find documentation for this module with the perldoc command.

    perldoc Test::Case

You can also look for information at:

CONTRIBUTE ^

The source for this module is on GitHub: https://github.com/jplindstrom/p5-Test-Case

Patches welcome, etc.

AUTHOR ^

Johan Lindstrom - johanl@cpan.org on behalf of Net-A-Porter - http://www.net-a-porter.com/

LICENSE AND COPYRIGHT ^

Copyright 2012- Net-A-Porter.

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See http://dev.perl.org/licenses/ for more information.

ACKNOWLEDGEMENTS ^

Thanks to Net-A-Porter for providing time during one of the regular Hack-days.

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