According to the spec,HSBtoRGB() "converts a color..." but what the relationship between
the two formats is not given, so from a testing perspective, it's impossible to project the
outcome.

Two things are necessary to test this method:

Some information describing exactly what hue, saturation, and brightness are needs to be present.

Also, the relationship of how h, s, and b values are mapped to red, green, and blue values
needs to be documented.