1. An article of manufacture comprising a computer readable storage medium including code executed to generate a value for use with a storage device testing process to test a storage device and to perform operations, the operations comprising: determining an ancestor node of a current node in a tree of nodes, wherein the ancestor node is at a higher level in the tree than the current node up to a root node of the tree, wherein each ancestor node at a level of the ancestor node is associated with a different set of ordered leaf nodes, wherein there is a unique block of storage value in the storage device associated with each leaf node; determining a first leaf node of the ordered leaf nodes associated with the determined ancestor node; determining whether the determined ancestor node is a rightmost ancestor node at the level of the ancestor node; using a first formula to determine a last leaf node of the ordered leaf nodes associated with the determined ancestor node in response to determining that the ancestor node is the rightmost ancestor node; using a second formula different from the first formula to determine the last leaf node in response to determining that the ancestor node is not the rightmost ancestor node; generating the block of storage value associated with a selected leaf node that is between the determined first and last leaf nodes in response to determining to climb to the ancestor node of the current node and in response to determining not to climb to a further ancestor node of the determined ancestor node; and returning the generated block of storage value to the storage device testing process to use to perform an Input/Output (I/O) operation with respect to the generated block of storage value for the purpose of testing the storage device.