# check_future_plan() works when only one core available

    $parallel
    [1] TRUE
    
    $cluster
    [1] TRUE
    
    $multisession
    [1] TRUE
    
    $local
    [1] TRUE
    

# check_future_plan() works

    $parallel
    [1] TRUE
    
    $cluster
    [1] TRUE
    
    $multisession
    [1] TRUE
    
    $local
    [1] TRUE
    

# mcmc errors for invalid parallel plans

    $parallel
    [1] TRUE
    
    $cluster
    [1] TRUE
    
    $multisession
    [1] TRUE
    
    $local
    [1] TRUE
    

---

    parallel mcmc samplers cannot be run with `plan(multicore)`

---

    parallel mcmc samplers cannot be run with a fork cluster