Modeling the Circuit Breaker: The Test Module

The preconditions

Let’s start off by taking a look at the preconditions.

%% Picks whether a command should be valid under the current state.
precondition(unregistered, ok, _, {call, _, Call, _}) ->
    Call =:= success;
precondition(ok, To, #data{errors=N, limit=L}, {call,_,err,_}) ->
    (To =:= tripped andalso N+1 =:= L) orelse