Abstract: Apparatus and methods enabling the efficient and repeatable measurement of mobility performance of wireless data communications equipment are described. This is particularly useful for testing the impact of roaming of Wireless Local Area Network (WLAN) devices, such as clients, between their counterparts, such as access points. The apparatus and methods include controlled emulation of roaming by WLAN devices, using a set of WLAN tester units, by activating and deactivating instances of emulated devices on different tester units to simulate the physical translation of the actual WLAN devices in an environment. Simulation of increasing and decreasing distance during the roaming process is also rendered possible. This enables various mobility performance measurements to be made on WLAN devices in a repeatable manner, free from artifacts due to device manufacturing tolerances.