Improve arg-shift test

New test case courtesy of @aaaaaa123456789

test/asm/arg-shift.asm

@@ -15,7 +15,18 @@ print_some: MACRO
 	PRINTT "\3\9"
 ENDM
 
+bad: MACRO
+	shift _NARG - 1
+	PRINTT \1
+	PRINTT "\n"
+ENDM
 
 	print_all This test, probably, passes\,, but who knows, ?
 
 	print_some R,e,d,n,e,x,G,a,m,e,B,o,y,D,e,v,e,l,o,p,e,m,e,n,t,S,y,s,t,e,m,\n
+
+	bad 1, 3, 5, 1, 2, 4, 5, 6, 3, 3, 3, 6, 2, 1, "H"
+	bad "E"
+	bad 0, 1, 2, 3, "L"
+	bad 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, "L"
+	bad as, asd, asdf, asdfg, asdgh, "O"

test/asm/arg-shift.out

@@ -1,2 +1,7 @@
  This test probably passes, but who knows ?
 RGBDS
+H
+E
+L
+L
+O