[pixel shader]
float4 main(uniform float4 u) : sv_target
{
    if (u.x > 0.0)
        return float4(0.1, 0.2, 0.3, 0.4);
    else
        return float4(0.9, 0.8, 0.7, 0.6);
}

[test]
uniform 0 float4 0.0 0.0 0.0 0.0
draw quad
probe all rgba (0.9, 0.8, 0.7, 0.6)
uniform 0 float4 0.1 0.0 0.0 0.0
draw quad
probe all rgba (0.1, 0.2, 0.3, 0.4)