If all of the final combiner values are set to 0, the R0 output of the last combiner stage should be used as the fragment color. Add a test to verify this behavior (set all registers to distinct colors and validate that only R0 contributes to the output)
If all of the final combiner values are set to 0, the R0 output of the last combiner stage should be used as the fragment color. Add a test to verify this behavior (set all registers to distinct colors and validate that only R0 contributes to the output)