The BB King box (fret 10)
e|---------------------10-12-----| D E B|------------10-12-13-----------| A B C G|-9-11-12-----------------------| E F# G D|-------------------------------| A|-------------------------------| E|-------------------------------|
The move that defines this box, on the B string: 12b14-13-10. That is the major 3rd (C#, bent), the minor 3rd (C), then the root (A). The whole blues in three notes.
You pass when
One chorus: major-ish over I, minor over IV, and it sounds deliberate
Key of A. Tab written in A.