Developing screening tests to assess the level of resistance of a perennial crop such as cocoa towards diseases is essential to reduce the length of the breeding cycle. In the case of witches' broom disease caused by Crinipellis perniciosa, major constraints are linked to the fact that symptoms develop only when meristematic tissues are attacked, to the time needed for symptoms to develop, and to the low correlation between levels of attacks on flower cushion, twigs and cherelles. Field assessment under natural conditions of infection can produce valuable information but the status of clones showing some resistance in the field should ideally be confirmed using an inoculation method in the nursery, especially when the inoculum pressure in the field is low. The experience obtained at the Cocoa Research Unit (CRU) with field observations and with artificial inoculations and other resistance tests over the past decade is described. Progress with artificial inoculation tests has been significant, but the development of a reliable in vitro test, including germination of spores in plant extracts, remains difficult due to the complexity of the Theobroma cacao-Crinipellis perniciosa pathosystem.