lavfi virtual device - the same parameters for ffmpeg and ffplay The command

ffplay -f lavfi -graph testsrc2=d=1[out0];sine=d=1[out1] test.mp4


works fine. But the same arguments for ffmpeg (instead of ffplay)

ffmpeg -f lavfi -graph testsrc2=d=1[out0];sine=d=1[out1] test.mp4


produce only the error


[NULL @ 00000000006934c0] Requested output format 'lavfi' is not a suitable output format
test.mp4: Invalid argument



What's wrong with it?



Note: 

From the FFmpeg documentation for the lavfi:


  Currently only video data is supported.


It seems that's not true nowadays, at least ffplay works fine with audio (see my first command).
Or I incorrectly interpret this sentence?

But just in case I tried using the filtergraph testsrc2=d=1[out0];testsrc=d=1[out1] instead, with the same results — ffplay — OK, ffmpeg — the same error.
The ffmpeg tool can work with multiple inputs and outputs so the parser looks for -i to demarcate input options. The lavfi device will read the graph from the input argument 

Use

ffmpeg -f lavfi -i "testsrc2=d=1[out0];sine=d=1[out1]" test.mp4