Certainly seems a bit like it Regarding the Ipopt problem, I followed the stacktrace and found that it comes down to the the __solve method in src/solve/flux.jl:

```
function __solve(prob::OptimizationProblem, opt, data = DEFAULT_DATA;
maxiters::Number = 0, cb = (args...) -> (false),
progress = false, save_best = true, kwargs...)
if data != DEFAULT_DATA
maxiters = length(data)
else
if maxiters <= 0.0
error("The number of maxiters has to be a non-negative and non-zero number.")
end
data = take(data, maxiters)
end
```

Corresponding error:

```
Rosenbrock: Error During Test at C:\Users\Stefan Mathis\.julia\packages\SafeTestsets\A83XK\src\SafeTestsets.jl:25
Got exception outside of a @test
LoadError: The number of maxiters has to be a non-negative and non-zero number.
Stacktrace:
[1] error(s::String)
@ Base .\error.jl:33
[2] __solve(prob::SciMLBase.OptimizationProblem{true, SciMLBase.OptimizationFunction{true, GalacticOptim.AutoForwardDiff{nothing}, typeof(Main.##297.rosenbrock), Nothing, Nothing, Nothing,
Main.##297.var"#1#2", Nothing, Nothing}, Vector{Float64}, SciMLBase.NullParameters, Nothing, Vector{Float64}, Vector{Float64}, Base.Iterators.Pairs{Union{}, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}}, opt::Type, data::Base.Iterators.Cycle{Tuple{GalacticOptim.NullData}}; maxiters::Int64, cb::Function, progress::Bool, save_best::Bool, kwargs::Base.Iterators.Pairs{Union{}, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
@ GalacticOptim C:\Users\Stefan Mathis\.julia\dev\GalacticOptim\src\solve\flux.jl:25
[3] __solve (repeats 2 times)
@ C:\Users\Stefan Mathis\.julia\dev\GalacticOptim\src\solve\flux.jl:18 [inlined]
[4] #solve#474
@ C:\Users\Stefan Mathis\.julia\packages\SciMLBase\oTP8b\src\solve.jl:3 [inlined]
[5] solve(::SciMLBase.OptimizationProblem{true, SciMLBase.OptimizationFunction{true, GalacticOptim.AutoForwardDiff{nothing}, typeof(Main.##297.rosenbrock), Nothing, Nothing, Nothing, Main.##297.var"#1#2", Nothing, Nothing}, Vector{Float64}, SciMLBase.NullParameters, Nothing, Vector{Float64}, Vector{Float64}, Base.Iterators.Pairs{Union{}, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}}, ::Type)
@ SciMLBase C:\Users\Stefan Mathis\.julia\packages\SciMLBase\oTP8b\src\solve.jl:3
[6] top-level scope
@ C:\Users\Stefan Mathis\.julia\dev\GalacticOptim\test\rosenbrock.jl:56
```

Examining the call signature of the __solve method, it seems obvious that this errors when called with `sol = solve(prob, Ipopt.Optimizer)`

in rosenbrock.jl, since neither `data`

nor `maxiters`

is provided. Therefore I don’t understand why your test run passed. What am I missing?