We present a novel test methodology for testing IP cores in SoCs with embedded processor cores. A test program is run on the processor core that generates and delivers test patterns to the target IP cores in the SoC and analyzes the test responses. This provides tremendous flexibility in the type of patterns that can be applied to the IP cores without incurring significant hardware overhead. We use a bus based SoC simulation model to validate our test methodology. The test methodology involves addition of a test wrapper that can be configured for specific test needs. The methodology supports at-speed testing for delay faults and stuck-at testing of IP cores implementing full-scan.