Tests that the parameters to CSSSupportsRule.insertRule() / deleteRule() are mandatory. On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS supportsRule.__proto__ is CSSSupportsRule.prototype PASS supportsRule.insertRule() threw exception TypeError: Not enough arguments. PASS supportsRule.cssRules.length is 1 PASS supportsRule.insertRule('body { width: 0; }') did not throw exception. PASS supportsRule.cssRules.length is 2 PASS supportsRule.deleteRule() threw exception TypeError: Not enough arguments. PASS successfullyParsed is true TEST COMPLETE