uniform float4 testInputs;  // equals (-1.25, 0, 0.75, 2.25)
uniform half4 colorGreen, colorRed;

half4 main(float2 coords) {
    const float4 constVal = half4(-1.25, 0, 0.75, 2.25);
    const float4 expected = half4( 0.75, 0, 0.75, 0.25);

    return (fract(testInputs.x)    == expected.x     &&
            fract(testInputs.xy)   == expected.xy    &&
            fract(testInputs.xyz)  == expected.xyz   &&
            fract(testInputs.xyzw) == expected.xyzw  &&
            fract(constVal.x)      == expected.x     &&
            fract(constVal.xy)     == expected.xy    &&
            fract(constVal.xyz)    == expected.xyz   &&
            fract(constVal.xyzw)   == expected.xyzw) ? colorGreen : colorRed;
}