Despite these controversies, progress of the extension's construction steadily approached completion throughout the rest of the year, reaching 78% in June, 86% in September and 92% by January 2019. A month later, it was deemed that the extension would be ready for testing that would last for several months, starting with two recently retired 5000 series railcars towed by a diesel to clean the third rail while it is disabled, before energizing it to allow for more dynamic train testing. Despite reports of trouble that prevented early test trains from going so far, testing eventually continued throughout the expansion and into Dulles Airport in March. The following month, progress of construction reached 95%.