Tests wanted / List of untested functionality

Many tests have been added, but there still remain many features that need to have tests added. The list below is meant to capture all features that do not yet have a test, or known breakages that do not yet have a corresponding test so that fixes can be pursued and validated.

## Real space statistical integration tests needed

Real space parallelization tests needed:
- [ ] Ensemble runs (minimal tests added in PR: #4091 , see also #1103 )
- [ ] GPU spline data sharing (PR: , see also #1229 )

Real space estimator tests needed:
- [ ] Chiesa kinetic energy correction (PR: , see also #1003 )
- [x] MPC potential energy correction (PR: #1470, see also #1002 )
- [ ] momentum distribution (PR: , see also #627 )
- [x] pair correlation function (PR: , see also #396 )
- [x] structure factor--SkEstimator (PR: #764 , see also #1000 )
- [ ] structure factor--StaticStructureFactor estimator, spin resolved (PR: , see also #999 )
- [x] structure factor--SkAllEstimator, finite size corrections (PR: , see also #1001 )
- [ ] energy density matrix (PR: , see also #981, #983 )
- [ ] traces (PR: , see also #1063 )
- [ ] forward walking (PR: , see also #1004 )
- [ ] core polarization potential (PR: , see also #1005 )
- [ ] force estimators in open BC's (PR: , see also #332 )
- [ ] force estimators in periodic BC's (PR: , see also #332 )
- [ ] RMC with basically any/all non-energy estimators
- [ ] CSVMC with basically any/all non-energy estimators

Real space wavefunction tests needed:
- [ ] excited states in Slater determinant (PR: #1702, up/down dets still needed, see also #740 )
- [ ] matrix tiling of B-spline orbitals (PR: , see also #575 )
- [ ] quasi-2D boundary conditions (?) (PR: , see also #578 )
- [ ] electron-ion backflow (PR: , see also #1226 )

Real space method tests needed:
- [ ] pade2 Jastrow optimization (PR: , see also #412)
- [x] orbital optimization with Bspline orbitals (PR: , see also #637, #638)
- [ ] CSVMC with openmp enabled (PR: , see also #362)
- [ ] DMC restart test (PR: , see also #798 )
- [x] DMC size consistent T-moves with splines (PR: #1288, see also #630 )

Tests that might be useful for bugfixes:
- [ ] DMC test demonstrating stochastic reconfiguration problem (PR: , see also #18 )
- [ ] RMC test demonstrating BlockWeight problem (PR: , see also #180)
- [ ] orbital optimization demonstrating incorrect energy with LCAO (PR: , see also #638)

## Real space deterministic integration tests needed
(plan out first set of tests to add here, see also #704 )

- [x] Chiesa kinetic energy correction
- [x] exited states for periodic system
- [x] 2D boundary condition

## Real space unit tests needed
(need to list)

## Auxiliary field integration tests needed
Auxiliary field estimator tests needed:
- [ ] Back propagated options (path restoration on/off, internal averaging...)

Auxiliary field unit tests needed:
- [ ] afqmctools python unit tests need to be turned on.
- [ ] Dense Hamiltonian unit tests

Auxiliary field method tests needed:
- [x] Workflow tests need to be turned on.
- [ ] Multi-node tests needed for distributed propagation / memory.

See #1062 for an overarching view of the testing problem and links to its other aspects.