SRAM based reprogrammable FPGAs are sensitive to radiation-induced Single Event Upsets (SEU), not only in their user flip-flops and memory, but also in the configuration memory. Appropriate mitigation has to be applied if they are used in space, for example the XTMR scheme implemented by the Xilinx TMRTool and configuration scrubbing. The FLIPPER fault injection platform, described in this paper, allows testing the efficiency of the SEU mitigation scheme. FLIPPER emulates SEU-like faults by doing partial reconfiguration and then applies stimuli derived from HDL simulation (VHDL/Verilog test-bench), while comparing the outputs with the golden pattern, also derived from simulation. FLIPPER has its Device-Under-Test (DUT) FPGA on a mezzanine board, allowing an easy exchange of the DUT device. Results from a test campaign are presented using a design from space application and applying various levels of TMR mitigation.