MCTSSolver fails test_solver on BabyPOMDP

[FlyingWorkshop]

I was trying to use MCTS to verify whether a custom POMDP could be solved using MCTSSolver and test_solver. I realized that MCTSSolver also appears to fail on standard POMDPs. Is this expected?

Code:

using POMDPModels
using POMDPTools
using POMDPs
using MCTS

pomdp = BabyPOMDP()
solver = MCTSSolver(n_iterations=10, depth=5, exploration_constant=5.0)
test_solver(solver, pomdp)

Throws

ERROR: LoadError: MethodError: no method matching updater(::MCTSPlanner{BabyPOMDP, Bool, Bool, MCTS.SolvedRolloutEstimator{RandomPolicy{Random._GLOBAL_RNG, BabyPOMDP, NothingUpdater}, Random._GLOBAL_RNG}, Random._GLOBAL_RNG})

Closest candidates are:
  updater(::CompressedBeliefPolicy)
   @ CompressedBeliefMDPs ~/Documents/VSCodeProjects/BeliefCompression/CompressedBeliefMDPs/src/solver.jl:45
  updater(::AlwaysFeed)
   @ POMDPModels ~/.julia/packages/POMDPModels/eZX2K/src/CryingBabies.jl:70
  updater(::FeedWhenCrying)
   @ POMDPModels ~/.julia/packages/POMDPModels/eZX2K/src/CryingBabies.jl:74
  ...

Stacktrace:
 [1] test_solver(solver::MCTSSolver, problem::BabyPOMDP; max_steps::Int64, updater::Nothing)
   @ POMDPTools.Testing ~/.julia/packages/POMDPTools/7Rekv/src/Testing/solver.jl:82
 [2] test_solver(solver::MCTSSolver, problem::BabyPOMDP)
   @ POMDPTools.Testing ~/.julia/packages/POMDPTools/7Rekv/src/Testing/solver.jl:78
 [3] top-level scope
   @ ~/Documents/VSCodeProjects/BeliefCompression/arena/circles/mcts.jl:8
 [4] include(fname::String)
   @ Base.MainInclude ./client.jl:489
 [5] top-level scope
   @ REPL[3]:1
 [6] top-level scope
   @ none:1
in expression starting at /Users/logan/Documents/VSCodeProjects/BeliefCompression/arena/circles/mcts.jl:8

[zsunberg]

This is expected. MCTS.jl is designed for MDPs. Use BasicPOMCP if you want to apply MCTS in the standard way to a POMDP.

(We could perhaps change the behavior so that this is more clear.)

[zsunberg]

Closing since this is expected behavior, but please re-open if you would like to discuss further!