public function make_absolute_url_testcases() {
    // 0: The Location header, 1: The current URL, 3: The expected URL.
    return array(
      // Absolute URL provided.
      array( 'http://site.com/', 'http://example.com/', 'http://site.com/' ),
      // No current URL provided.
      array( '/location', '', '/location' ),

      // No location provided.
      array( '', 'http://example.com', 'http://example.com/' ),

      // Location provided relative to site root.
      array( '/root-relative-link.ext', 'http://example.com/', 'http://example.com/root-relative-link.ext' ),
      array( '/root-relative-link.ext?with=query', 'http://example.com/index.ext?query', 'http://example.com/root-relative-link.ext?with=query' ),

      // Location provided relative to current file/directory.
      array( 'relative-file.ext', 'http://example.com/', 'http://example.com/relative-file.ext' ),
      array( 'relative-file.ext', 'http://example.com/filename', 'http://example.com/relative-file.ext' ),
      array( 'relative-file.ext', 'http://example.com/directory/', 'http://example.com/directory/relative-file.ext' ),

      // Location provided relative to current file/directory but in a parent directory.
      array( '../file-in-parent.ext', 'http://example.com', 'http://example.com/file-in-parent.ext' ),
      array( '../file-in-parent.ext', 'http://example.com/filename', 'http://example.com/file-in-parent.ext' ),
      array( '../file-in-parent.ext', 'http://example.com/directory/', 'http://example.com/file-in-parent.ext' ),
      array( '../file-in-parent.ext', 'http://example.com/directory/filename', 'http://example.com/file-in-parent.ext' ),

      // Location provided in muliple levels higher, including impossible to reach (../ below DOCROOT).
      array( '../../file-in-grand-parent.ext', 'http://example.com', 'http://example.com/file-in-grand-parent.ext' ),
      array( '../../file-in-grand-parent.ext', 'http://example.com/filename', 'http://example.com/file-in-grand-parent.ext' ),
      array( '../../file-in-grand-parent.ext', 'http://example.com/directory/', 'http://example.com/file-in-grand-parent.ext' ),
      array( '../../file-in-grand-parent.ext', 'http://example.com/directory/filename/', 'http://example.com/file-in-grand-parent.ext' ),
      array( '../../file-in-grand-parent.ext', 'http://example.com/directory1/directory2/filename', 'http://example.com/file-in-grand-parent.ext' ),

      // Query strings should attach, or replace existing query string.
      array( '?query=string', 'http://example.com', 'http://example.com/?query=string' ),
      array( '?query=string', 'http://example.com/file.ext', 'http://example.com/file.ext?query=string' ),
      array( '?query=string', 'http://example.com/file.ext?existing=query-string', 'http://example.com/file.ext?query=string' ),
      array( 'otherfile.ext?query=string', 'http://example.com/file.ext?existing=query-string', 'http://example.com/otherfile.ext?query=string' ),

      // A file with a leading dot.
      array( '.ext', 'http://example.com/', 'http://example.com/.ext' ),

      // URLs within URLs.
      array( '/expected', 'http://example.com/sub/http://site.com/sub/', 'http://example.com/expected' ),
      array( '/expected/http://site.com/sub/', 'http://example.com/', 'http://example.com/expected/http://site.com/sub/' ),

      // Schemeless URL's (not valid in HTTP Headers, but may be used elsewhere).
      array( '//example.com/sub/', 'https://example.net', 'https://example.com/sub/' ),
    );
  }