An apparatus for testing of downhole multiphase fluid handling systems used in oil and gas production allows test personnel to visually observe the testing. The apparatus is constructed from housings and/or casings made partly or entirely of a see-through material. The see-through material allows for unaided visual observation of the flow regime of the fluid flowing through fluid handling equipment. This eliminates most all of the assumptions that typically need to be made about how well the equipment operates. The ability to clearly observe the flow regimes unassisted allows for accurate study of individual equipment effects, vortices interactions and formation, the effects of different velocities of fluid flow, the optimization of flow paths, remixing and flow regimes external of a system, slug creation, and other parameters known to those skilled in the art.