text: <?php
  
  return [
  	'vfs_dir'   => 'wp-content/cache/critical-css/',
  
  	// Virtual filesystem structure.
  	'structure' => [
  		'wp-content' => [
  			'cache' => [
  				'critical-css' => [
  					'1' => [
  						'.'            => '',
  						'..'           => '',
  						'critical.css' => 'body { font-family: Helvetica, Arial, sans-serif; text-align: center;}',
  						'posts'        => [],
  					],
  					'2' => [
  						'critical.css' => 'body { font-family: Helvetica, Arial, sans-serif; text-align: center;}',
  					],
  				],
  			],
  		],
  	],
  
  	// Test data.
  	'test_data' => [
  		'non_multisite' => [
  			'testShouldDoNothingWhenAsynCssOff' => [
  				'values'   => [
  					'old' => [
  						'async_css'               => 0,
  						'do_caching_mobile_files' => 0,
  						'async_css_mobile'        => 0,
  					],
  					'new' => [
  						'async_css'               => 0,
  						'do_caching_mobile_files' => 0,
  						'async_css_mobile'        => 0,
  					],
  				],
  				'mobile'   => false,
  				'expected' => false,
  			],
  			'testShouldDoNothingWhenAsynCssDisabled' => [
  				'values'   => [
  					'old' => [
  						'async_css'               => 1,
  						'do_caching_mobile_files' => 0,
  						'async_css_mobile'        => 0,
  					],
  					'new' => [
  						'async_css'               => 0,
  						'do_caching_mobile_files' => 0,
  						'async_css_mobile'        => 0,
  					],
  				],
  				'mobile' => false,
  				'expected' => false,
  			],
  			'testShouldDoNothingWhenAsynCSSEnabledAndDidntChange' => [
  				'values'   => [
  					'old' => [
  						'async_css'               => 1,
  						'do_caching_mobile_files' => 0,
  						'async_css_mobile'        => 0,
  					],
  					'new' => [
  						'async_css'               => 1,
  						'do_caching_mobile_files' => 0,
  						'async_css_mobile'        => 0,
  					],
  				],
  				'mobile'   => false,
  				'expected' => false,
  			],
  
  			'testShouldGenerateWhenFilesDontExist' => [
  				'values'   => [
  					'old' => [
  						'async_css'               => 0,
  						'do_caching_mobile_files' => 0,
  						'async_css_mobile'        => 0,
  					],
  					'new' => [
  						'async_css'               => 1,
  						'do_caching_mobile_files' => 0,
  						'async_css_mobile'        => 0,
  					],
  				],
  				'mobile'   => 'default',
  				'expected' => true,
  			],
  
  			'testShouldGenerateWhenFilesDontExistAndMobile' => [
  				'values'   => [
  					'old' => [
  						'async_css'               => 0,
  						'do_caching_mobile_files' => 0,
  						'async_css_mobile'        => 0,
  					],
  					'new' => [
  						'async_css'               => 1,
  						'do_caching_mobile_files' => 1,
  						'async_css_mobile'        => 1,
  					],
  				],
  				'mobile'   => 'all',
  				'expected' => true,
  			],
  		],
  
  		'multisite' => [
  			[
  				'values'          => [
  					'old' => [ 'async_css' => 0 ],
  					'new' => [ 'async_css' => 0 ],
  				],
  				'blog_id'         => 2,
  				'should_generate' => false,
  			],
  			[
  				'values'          => [
  					'old' => [ 'async_css' => 1 ],
  					'new' => [ 'async_css' => 1 ],
  				],
  				'blog_id'         => 2,
  				'should_generate' => false,
  			],
  			[
  				'values'          => [
  					'old' => [ 'async_css' => 0 ],
  					'new' => [ 'async_css' => 1 ],
  				],
  				'site_id'         => 3,
  				'should_generate' => true,
  			],
  			[
  				'values'          => [
  					'old' => [ 'async_css' => 0 ],
  					'new' => [ 'async_css' => 1 ],
  				],
  				'site_id'         => 4,
  				'should_generate' => true,
  			],
  		],
  	],
  ];
  