It seems there is a rare error occurring in TestMultiChequeSimulation when running the function as it is on the swap-multi-cheque-bug branch.

Test by opening a terminal in github.com/ethersphere/swarm and running:

for i in `seq 1000`; do /usr/local/go/bin/go test -count=1 -timeout 15s github.com/ethersphere/swarm/swap -run ^TestMultiChequeSimulation$; done > log.txt

(be aware that the default timeout for go test is 10 minutes, while this test in particular is programmed to time out at 10 seconds)

To run until the first failure:

while /usr/local/go/bin/go test -count=1 github.com/ethersphere/swarm/swap -run ^TestMultiChequeSimulation$; do :; done