The evaluation of hearing aids (HAs) inside realistic sound environments is of increasing interest. Higher-order Ambisonics (HOA) has been used for loudspeaker-based sound field resynthesis and HOA recording microphone arrays are available. Although HOA has been evaluated perceptually, it is unclear how far the results can be transferred to evaluating HA technologies (particularly multi-microphone enhancement algorithms). In order to determine the minimum HOA order required for HA testing, an HOA framework was developed, simulating the entire path from sound presented in a room, picked up by a microphone array, decoded and received at the ears of a HA-fitted dummy head. HA directivity patterns were compared between an ideal free-field and its HOA representation to evaluate the introduced error. In-room analysis was conducted to investigate the bandwidth and performance of a directional microphone in realistic situations. For a bandwidth B, the required order was found to be M≤B/600Hz for the anechoic (worst) case scenario. The presence of reverberation introduced natural room response variations across different source-receiver locations, suggesting that the acceptable HOA error can be increased. Hence, in reverberant environments the required HOA order is reduced and at least 2D HOA reproduction can be used for evaluation of HA technologies.