Fix signed integer parsing

test/test_cpu.ml

@@ -0,0 +1,19 @@
+open OUnit2
+
+
+let test_signed test_ctx =
+  let n = 0xFA in
+  let s = Cpu.signed_byte n in
+  assert_equal s (-6)
+
+
+(* Name the test cases and group them together *)
+let suite =
+"suite">:::
+ [
+   "test signed">:: test_signed
+ ]
+
+let () =
+  run_test_tt_main suite
+