The Linux UEFI Validation Project was announced recently:
Bringing together multiple separate upstream test suites into a cohesive and easy-to-use product with a unified reporting framework, LUV validates UEFI firmware at critical levels of the Linux software stack and boot phases.
LUV also provides tests in areas not previously available, such as the interaction between the bootloader, Linux kernel and firmware. Integrated into one Linux distribution, firmware can now be tested under conditions that are closer to real scenarios of operation. The result: fewer firmware issues disrupting the operating system.
Of course that "one Linux distribution" is built using the Yocto Project, so it's trivial to grab the source and patch/extend it, or rebuild it for different processors if for example you want to validate UEFI on ARM or a new CPU that mainstream distros don't fully support.