stage | owner | receiver | allowance | status
initial | 100 | 0 | 0 | -
transfer 5 | 95 | 5 | 0 | 1
approve 30 | 95 | 5 | 30 | 1
spend 10 | 85 | 15 | 20 | 1
overspend 21 | 85 | 15 | 20 | 0
revoke | 85 | 15 | 0 | 1
spend after revoke | 85 | 15 | 0 | 0
Assertions: PASS