assert_equal("foo.jpg", legal_file::change_extension("foo.png", "jpg")); } public function change_four_letter_extension_test() { $this->assert_equal("foo.flv", legal_file::change_extension("foo.mpeg", "flv")); } public function change_extension_with_no_extension_test() { $this->assert_equal("foo.flv", legal_file::change_extension("foo", "flv")); } }