The video, taken in the coastal city of Sinop on Friday, showed a narrow column of smoke headed high into the blue sky.
Turkey was widely expected to test the system this week, after issuing notices warning vessels and aircraft to avoid the area in the Black Sea.
Turkey’s defence ministry said it would neither deny nor confirm missile tests.
Tests of the S-400s could stoke tensions between Turkey and the United States, which sharply opposed Ankara’s purchase of the weapons from Moscow on grounds they compromise shared NATO defence systems.
Washington reacted last year by suspending Turkey from its F-35 jet programme and has threatened sanctions.
On Friday, the US State Department warned of “potential serious consequences” for its security relationship with Turkey if it activates the system.
“If confirmed, we would condemn in the strongest terms the S-400 test missile launch as incompatible with Turkey’s responsibilities as a NATO ally and strategic partner of the United States,” State Department spokeswoman Morgan Ortagus said in a statement.