We propose and evaluate a framework to test the functional correctness of coarse-grained reconfigurable array (CGRA) processors for pre-silicon verification and post-silicon validation. To reflect the reconfigurable nature of CGRAs, an architectural model of the system under test is built directly from the hardware description files. A guided place-and-routing algorithm is used to map operations and operands onto the heterogeneous processing elements (PE). Test coverage is maximized by favoring unexercised parts of the architecture. Requiring no explicit knowledge about the semantics of operations, the random test program generator (RTPG) framework seamlessly supports custom ISA extensions. The proposed framework is applied to the Samsung Reconfigurable Processor, a modulo-scheduled CGRA integrated in smartphones, cameras, printers, and smart TVs. Experiments demonstrate that the RTPG is versatile, efficient, and quickly achieves a high coverage. In addition to detecting all randomly inserted faults, the generated test programs also exposed two yet unknown actual faults in the architecture.