"open new tab"
WebUI.click(findTestObject('a'))
WebUI.waitForPageLoad(10)
"move into the new tab"
WebUI.switchToWindowIndex(1)
"verify element within the new tab"
WebUI.waitForElementVisible(findTestObject('b'), 10)
WebUI.verifyElementVisible(findTestObject('b'))
and then, depending if your additional tabs close or not, you can:
'close the second tab'
WebUI.closeWindowIndex(1)
'switch back to default content'
WebUI.switchToDefaultContent()