A circuit breaker doesn't trip on httpConsecutiveErrors: 1 (for 500 response). All requests pass through and give a 500 instead. The circuit breaker should trip and should return 503(Service Unavailable) instead.
Follow the steps Circuit breaker setup.
Once httpbin is up you can simulate 500 with it Request :
kubectl exec -it $FORTIO_POD -c fortio /usr/local/bin/fortio -- load -c 1 -qps 0 -n 20 -loglevel Warning http://httpbin:8000/status/500
Running this will simulate 20 requests returning 500.
But if you have applied the circuit breaker if should allow just the one request as 500 and remaining requests should be tripped and a 503 should be returned. This doesn't happen.