Simple test framework, functional programming style

functional-tests.php

<?php

function within($topic, ...$features)
{
    return function($do = 'getFailedAssertions') use ($topic, $features) {
        if ($do === 'getName') {
            return $topic;
        } elseif ($do === 'getFailedAssertions') {
            return array_reduce(
                $features,
                function($failedAssertions, $feature) {
                    return array_merge(
                        $failedAssertions,
                        array_map(
                            function($assertion) use ($feature) {
                                return array($assertion, $feature);
                            },
                            $feature('getFailedAssertions')
                        )
                    );
                },
                array()
            );
        } elseif ($do === 'numberOfFeatures') {
            return count($features);
        } elseif ($do === 'numberOfAssertions') {
            return array_reduce(
                $features,
                function($number, $feature) {
                    return $number + $feature('numberOfAssertions');
                },
                0
            );
        } else {
            throw new InvalidArgumentException('Invalid argument ' . $do);
        }
    };
}

function describe($feature, ...$assertions)
{
    return function($do = 'getFailedAssertions') use ($feature, $assertions) {
        if ($do === 'getName') {
            return $feature;
        } elseif ($do === 'getFailedAssertions') {
            return array_filter(
                $assertions,
                function($assertion) {
                    return !$assertion('assert');
                }
            );
        } elseif ($do === 'numberOfAssertions') {
            return count($assertions);
        } else {
            throw new InvalidArgumentException('Invalid argument ' . $do);
        }
    };
}

function it($doesThis, $correctly)
{
    return function($do = 'assert') use ($doesThis, $correctly) {
        if ($do === 'assert') {
            return (bool) $correctly;
        } elseif ($do === 'getDescription') {
            return (string) $doesThis;
        } else {
            throw new InvalidArgumentException('Invalid argument ' . $do);
        }
    };
}

function testResults(array $topics)
{
    return function($do = '') use ($topics) {
        if ($do === 'numberOfTopics') {
            return count($topics);
        } elseif ($do === 'numberOfFeatures') {
            return array_reduce(
                $topics,
                function($number, $topic) {
                    return $number + $topic('numberOfFeatures');
                },
                0
            );
        } elseif ($do === 'numberOfAssertions') {
            return array_reduce(
                $topics,
                function($number, $topic) {
                    return $number + $topic('numberOfAssertions');
                },
                0
            );
        } elseif ($do === 'failedAssertions') {
            return array_reduce(
                $topics,
                function($failedAssertions, $topic) {
                    $assertions = $topic('getFailedAssertions');

                    $assertions = array_map(
                        function($assertion) use ($topic) {
                            $assertion[] = $topic;

                            return $assertion;
                        },
                        $assertions
                    );

                    return array_merge($failedAssertions, $assertions);
                },
                array()
            );
        } else {
            throw new InvalidArgumentException('Invalid argument ' . $do);
        }
    };
}

function displayTestResults($testResults)
{
    $output = '';

    $output .= 'topics: ' . $testResults('numberOfTopics') . "\n";
    $output .= 'features: ' . $testResults('numberOfFeatures') . "\n";
    $output .= 'assertions: ' . $testResults('numberOfAssertions') . "\n";
    $output .= "\n";

    $output .= implode(
        "\n",
        array_map(
            function($assertion) {
                return failedOutput($assertion[2], $assertion[1], $assertion[0]);
            },
            $testResults('failedAssertions')
        )
    );
    $output .= "\n";

    echo $output;
}

function failedOutput($topic, $feature, $assertion)
{
    return 'FAILED: '
           . $topic('getName')
           . ': ' . $feature('getName')
           . ' ' . $assertion('getDescription')
    ;
}

function getTopics()
{
    $files = glob('topic*.php');

    return array_map(
        function($file) {
            return include($file);
        },
        $files
    );
}

run-tests.php

<?php

require_once 'functional-tests.php';

displayTestResults(testResults(getTopics()));

topic-calculus.php

<?php

return within("calculus",
    describe("addition",
        it("adds two numbers", (1 + 1 == 3)),
        it("is difficult", false),
        it("adds three numbers", (1 + 1 + 1 == 3))
    ),
    describe("subtraction",
        it("looks strange", true),
        it("subtracts two numbers", (3 - 2 == 1))
    )
);

running php run-tests.php will produce this output:

topics: 1
features: 2
assertions: 5

FAILED: calculus: addition adds two numbers
FAILED: calculus: addition is difficult

It will also work with multiple topic-* files

• Line 60: $correctly should probably be a callback instead of a bool.
• rename $do to $message
• Instead of all the ugly if/elseifs, abstract the pattern into a function called dispatch. See https://github.com/mathiasverraes/lambdalicious/blob/master/src/Verraes/Lambdalicious/datastructures.php#L19-L28 for an example

you're right about those 3 things. Also, i didn't see the dispatch method yet, it's really quite elegant!