const PAGE = "data:text/html,page"; function* test_on_browser(browser) { ok(!browser.audioMuted, "Audio should not be muted by default"); browser.mute(); ok(browser.audioMuted, "Audio should be muted now"); yield BrowserTestUtils.withNewTab({ gBrowser, url: PAGE, }, test_on_browser2); browser.unmute(); ok(!browser.audioMuted, "Audio should be unmuted now"); } function* test_on_browser2(browser) { ok(!browser.audioMuted, "Audio should not be muted by default"); } add_task(function*() { yield BrowserTestUtils.withNewTab({ gBrowser, url: PAGE, }, test_on_browser); });