The contamination of foodstuffs, additives, cosmetics, pharmaceuticals and the like by undesirable micro-organisms is threat to public health. On occasion, the level of bacteria that conventional testing techniques are designed to look for is so low that the test result for the bacterium is “negative”. However, the bacterium although present in un-detectably small amounts may multiply under the right conditions and given the shelf life of the product, may be able to recover to an extent whereby public health is threatened. This problem is alleviated by the provision of micro-organism testing apparatus comprising (a) an incubator, and (b) a multi-compartment resealable container provided with or adapted to receive a growth medium in one compartment and having a growth medium additive in another compartment, the compartments being separated by a barrier whose removal or puncture will expose the medium to the additive.