An accurate assessment of catalyst performance is the most important goal in the testing of fluid catalytic cracking (FCC) catalysts since the catalyst is a key contributor to the overall unit performance. For this purpose small scale tests in the laboratory have been the workhorse in the industry because they are less expensive and time-consuming to operate than circulating riser pilot units. Two reactor types are common in microactivity testing, simple fixed bed (plug-flow) reactors and fixed fluidised bed reactors. Pitfalls have been identified for both experimental modes and this paper discusses the strengths and weaknesses of these two techniques. This work demonstrates that catalyst testing in small-scale fixed fluidised bed reactors san result in erroneous catalyst ranking, while the use of improved fixed bed reactors has a better agreement with riser pilot units. Furthermore, reactors of either type that employ in-situ regeneration result in unrealistically high coke and hydrogen yields due to the oxidation of contaminant metals, and therefore advanced deactivation procedures for metallated FCC catalysts cannot be utilised in small-scale tests with this technique.