In some examples, a diagnostic device includes a reusable part to receive a container of a fluid, the reusable part reusable for a plurality of diagnostic tests. The diagnostic device further includes a disposable part detachably attached to the reusable part and comprising a sample collector to collect a target sample of a living being. The diagnostic device further includes a tester comprising a fluid channel to transport the fluid to combine the fluid and the target sample to form a fluid combination, and to use the fluid combination to diagnose a condition of the target sample.