An image sensor may be implemented using a stitched image sensor die. The stitched image sensor die may be formed from a step and repeat exposure process using a set of tiles in a reticle set. Multiple instantiations of a same circuitry block on a given tile may be patterned and formed on the image sensor die. The image sensor die may include circuitry configured to enable testing of one or more instantiations of the same circuitry block. The image sensor die may include memory circuitry for storing indications of a functional instantiation of the multiple instances and may use the functional instantiation for normal operation.