Category Tree - PHPUnit Test Case

category_tree.php

<?php
class CategoryTreeTest extends PHPUnit_Framework_TestCase
{
    /**
     * @return array
     */
    public function getCategories(){

        $root = [
            'id' => 'root',
            'parent' => null,
            'children' => [],
        ];

        $books = [
            'id' => 'books',
            'parent' => 'root',
            'children' => [],
        ];

        $movies = [
            'id' => 'movies',
            'parent' => 'root',
            'children' => [],
        ];

        $fantasy = [
            'id' => 'fantasy',
            'parent' => 'books',
            'children' => [],
        ];

        $tolkien = [
            'id' => 'tolkien',
            'parent' => 'fantasy',
            'children' => [],
        ];


        $root['children'] = [&$books, &$movies];
        $books['children'] = [&$fantasy];
        $fantasy['children'] = [&$tolkien];

        return $root;
    }

    /**
     * @return array
     */
    public function getProductsAssignments()
    {
        return [
            'B001' => ['movies', 'fantasy'],
            'D8' => ['tolkien', 'root'],
            'H12' => ['books', 'tolkien', 'root', 'movies', 'fantasy'],
            'RX20' => [],
        ];
    }

    /**
     * @param string $categoryId
     * @param array $currentCategory
     * @return array | false
     */
    public function getCategoryById($categoryId, $currentCategory = null)
    {
        if (!$currentCategory) {
            $currentCategory = $this->getCategories();
        }

        if ($currentCategory['id'] == $categoryId) {
            return $currentCategory;
        }

        $result = array_reduce($currentCategory['children'], function ($result, $child) use ($categoryId) {
            $category = $this->getCategoryById($categoryId, $child);

            if ($category) {
                $result = $category;
            }

            return $result;
        }, false);

        return $result;
    }

    /**
     * @param $productId
     * @return array
     */
    protected function getProductCategories($productId)
    {
        $assignments = $this->getProductsAssignments();

        if (!array_key_exists($productId, $assignments)) {
            return [];
        }

        return array_reduce($assignments[$productId], function ($result, $categoryId) {
            $currentCategory = $this->getCategoryById($categoryId);

            if ($currentCategory !== false) {
                $result[] = $currentCategory;
            }

            return $result;
        }, []);
    }

    /**
     * @param $productId
     * @return array
     */
    public function getPaths($productId)
    {
        $paths = array_reduce($this->getProductCategories($productId), function ($result, $category) {
            do {
                $path[] = $category['id'];
            }
            while ($category = $this->getCategoryById($category['parent']));

            if (count($path) > 1) {
                $result[] = array_reverse($path);
            }

            return $result;
        }, []);

        if (!count($paths)) {
            return ['EMPTY'];
        }

        $paths = $this->transformIntoString($this->removeDuplicatedTrees($paths));

        usort($paths, function ($pathA, $pathB) {
            return strcmp($pathA, $pathB);
        });

        return $paths;
    }

    /**
     * @param $paths
     * @return mixed
     */
    protected function transformIntoString($paths)
    {
        return array_reduce($paths, function ($result, $path) {
            $result[]  = implode(';', $path);
            return $result;
        }, []);
    }

    /**
     * @param $paths
     * @return array
     */
    protected function removeDuplicatedTrees($paths)
    {
        for ($i = 0; $i < count($paths); $i++) {
            for ($j = count($paths) - 1; $j > $i; $j--) {
                if (count(array_intersect($paths[$i], $paths[$j])) > 1) {
                    $paths[$i] = $paths[$i] + $paths[$j];
                    unset($paths[$j]);
                }
            }
        }

        return $paths;
    }

    public function testGetCategoryById()
    {
        $root = $this->getCategories();
        $this->assertEquals($root, $this->getCategoryById('root'));
        $this->assertEquals($root['children'][0], $this->getCategoryById('books'));
        $this->assertEquals($root['children'][1], $this->getCategoryById('movies'));

        $this->assertEquals($root['children'][0]['children'][0], $this->getCategoryById('fantasy'));
        $this->assertEquals($root['children'][0]['children'][0]['children'][0], $this->getCategoryById('tolkien'));
    }

    public function testPathIsEmptyWhenNoProductIdIsSpecified()
    {
        $this->assertEquals(['EMPTY'], $this->getPaths(''));
    }

    public function testPathIsEmptyWhenInvalidProductIdIsSpecified()
    {
        $this->assertEquals(['EMPTY'], $this->getPaths('XXXXXXXX'));
    }

    public function testPathIsEmptyWhenProductCategoryIsRoot()
    {
        $this->assertEquals(['EMPTY'], $this->getPaths('RX20'));
    }

    public function testPathsReturnsInAlphabeticalOrder()
    {
        $this->assertEquals(
            [
                'root;books;fantasy',
                'root;movies',
            ], $this->getPaths('B001'));
    }

    public function testGetPathsOnFourthLevel()
    {
        $this->assertEquals(['root;books;fantasy;tolkien'], $this->getPaths('D8'));
    }

    public function testOnlyTheLongestPathIsReturnedWhenProductHas2CategoriesIntTeSameTree()
    {
        $this->assertEquals(['root;books;fantasy;tolkien', 'root;movies'], $this->getPaths('H12'));
    }
}