>># 
>># Copyright 1990, 1991 by the Massachusetts Institute of Technology and
>># UniSoft Group Limited.
>># 
>># Permission to use, copy, modify, distribute, and sell this software and
>># its documentation for any purpose is hereby granted without fee,
>># provided that the above copyright notice appear in all copies and that
>># both that copyright notice and this permission notice appear in
>># supporting documentation, and that the names of MIT and UniSoft not be
>># used in advertising or publicity pertaining to distribution of the
>># software without specific, written prior permission.  MIT and UniSoft
>># make no representations about the suitability of this software for any
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>># 
>># $XConsortium: blckpxl.m,v 1.7 92/06/11 15:55:32 rws Exp $
>># 
>>#
>>TITLE BlackPixel CH02
>>ASSERTION A BlackPixel-1
A call to BlackPixel returns the black pixel value for the
default colourmap of the screen screen_number.
>>STRATEGY
Obtain the value of the black pixel using BlackPixel.
Verify that the value is that given in parameter XT_BLACK_PIXEL.
