Crosstalk effects on long interconnects are becoming significant for high-speed circuits. This paper addresses the problem of testing crosstalk-induced faults at on-chip buses in system-on-a-chip (SOC) designs. We propose a method to self-test on-chip buses at-speed, by executing an automatically synthesized program using on-chip processor cores. The test program, executed at system operational speed, can activate and capture the worst-case crosstalk effects on buses and achieve a complete coverage of crosstalk-induced logical and delay faults. This paper discusses the method and the framework for synthesizing such a test program. Based on the bus protocol, the instruction set architecture of an on-chip processor core, and the system specification, the method generates deterministic tests in the form of instruction sequences. The synthesized test program is highly modularized and compact. The experimental results show that, for testing interconnects between a processor core and any other on-chip core, a 3K-byte program is sufficient to achieve the complete coverage for crosstalk-induced logical and delay faults.