Test for validationMessage IDL attribute for On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". No message PASS testIt("", "", "") is "" Value missing FAIL testIt("", "", "") should be value missing. Was Fill out this field. Type mismatch PASS testIt("foo", "", "") is "" Range overflow FAIL testIt("1982-11-02", "", "1970-12-31") should be range overflow. Was Value must be less than or equal to 1970-12-31. Range underflow FAIL testIt("1982-11-02", "1990-05-25", "1990-12-24") should be range underflow. Was Value must be greater than or equal to 1990-05-25. Step mismatch FAIL testIt("1982-11-02", "", "", "123") should be step mismatch. Was Enter a valid value. PASS successfullyParsed is true TEST COMPLETE