clack 100
This may be what you are looking for
"An automatic test of the A/T flashing amber function is performed if the A/T
is engaged and the following conditions exist:
-MCP SPD or FMC SPD is the A/T active mode
-More than 150 seconds after lift off
-Flaps extended
A/T amber light flashes for 2 seconds, remains extinguished for 2 seconds and then flashes for 2 seconds again"
That is straight from our ops manual, and the conditions are met when going from flap up to flap 1 as you describe.