The present disclosure provides for a guide for use in a compression test, the compression test comprising loading a test sample between a first loading plate and an opposing load applied between the test sample and the first loading plate in a loading direction, the guide comprising: at least one support member, positionable between the first loading plate and the load and extending substantially parallel to the loading direction to constrain the test sample in a direction perpendicular to the loading direction, wherein, when in use, the at least one support member is positioned to define a space between the first loading plate and the support member such that when a load is applied the test sample is deformable in a direction perpendicular to the loading direction within the space.