Similar for buffMB vs. header width

Author: MichaelChirico

inst/tests/tests.Rraw

@@ -10108,10 +10108,15 @@ test(1658.61, fwrite(data.table(a="a"), na="VERY LONG MISSING VALUE STRING !", q
      output="maxLineLen=66")
 ## eol="" error
 test(1658.62, fwrite(data.table(a=1), tempfile(), eol=''), error='eol must be 1 or more bytes')
-## buffMB < single line width
+## buffMB < single line width and < header width
 f = tempfile()
 test(1658.63, fwrite(data.table(a=strrep('x', 2**21)), f, buffMB=1.0), NULL)
 test(1658.64, file.size(f) > 2**20) # almost exactly 2**21, but exact number will vary by platform. we just care we didn't truncate at 1MiB.
+DT=data.table(1L)
+setnames(DT, strrep('y', 2**21))
+test(1658.65, fwrite(DT, f, buffMB=1.0, nThread=1L), NULL)
+test(1658.66, file.size(f) > 2**20)
+unlink(f)
 
 options(oldverbose)
 ## End fwrite tests