<?php
/** the function under test */
  public function set($key, $value)
  {
    file_put_contents(
      $key,
      '<?php return ' . var_export($value, true) . ';'
    );
  }

/** a single test to check that the $key is used as filename */

  /**
   * @requires extension uopz
   */
  public function testSetUsesKeyAsFileNameToPersistCacheIn()
  {
    uopz_backup('file_put_contents');
    $that = $this;
    uopz_function(
      'file_put_contents',
      function(
        $filename,
        $flags = false,
        $context = null,
        $offset = -1
        //$maxlen = null
      ) use ($that) {
        $that->assertSame(
          $filename,
          'testFileName'
        );
      }
    );
    uopz_restore('file_put_contents');

    $this->cache->set('testFileName', 'test');
  }