According to US sources, quoted by CNBC, Russia conducted a test of the Nudol ASAT system on December 23, 2018. The missile was launched from a mobile launcher from a test site in Plesetsk. The launch complex used to test the Nudol missile was found near the site used for Thyklon space launches. [UPDATE 04/20/20: It turned out that it's not a Nudol launch pad.]

That would be the second Nudol test in 2018 - the first one took place in April 2018. CNBC also quotes a source as saying that it was "the seventh overall test of the system." There were indeed three launches in 2014-2015 (one of them unsuccessful) and two in 2016 - in May and in December. Apparently there were no launches in 2017.

In the December 2018 test, the missile was said to be in flight for 17 minutes and landed at 3000 km (1,864 miles in the CBNC report) from Plesetsk. This matches the splash-down area in the Laptev Sea that was closed during the 23-25 December 2018. A similar area was closed for the April 2018 test.

I should also note that it appears that Nudol tests are not included in the Roskosmos launch statistics - if they were, the total count would be three launches from Plesetsk in 2018 - one Yars in June and two Nudols. But Rogozin counted only two.