Managers of Auckland's City Rail Link are still shying away from naming a specific opening date, following last night's successful tests. 

A train made five trips through the new tunnels overnight - between Waitematā and Maungawhau Station. 

It started at a gruelling five kilometres an hour, but picked up the pace as technicians made their checks. 

CRL Chief Executive Patrick Brockie says it will open in 2026, but he won't be more specific. 

"The last year is complex, we've got a lot to do still and there can be the unknowns. But we're working as hard as we can to open as early as possible."

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