On-chip field testing methods and apparatus are disclosed. Example on-chip testers disclosed herein include a decoder having a test data input and a test stimuli interface. Disclosed example on-chip testers also include a multiplexer having a first multiplexer interface coupled to the test stimuli interface, a second multiplexer interface coupled to an automatic test equipment interface, a third multiplexer interface coupled to a design-for-testing subsystem interface and an interface selection input. Disclosed example on-chip testers further include a memory having a memory interface coupled to the test data input.