Add test case for math.mode

Cover the case in which there are two bytes that appear the same number of times. The lowest byte should be the mode.

Author: plusvic

tests/test-math.c

@@ -167,6 +167,14 @@ int main(int argc, char** argv)
       }",
       "ABABA");
 
+  assert_true_rule_blob(
+      "import \"math\" \
+      rule test { \
+        condition: \
+          math.mode() == 0x41 \
+      }",
+      "ABAB");
+
   assert_true_rule_blob(
       "import \"math\" \
       rule test { \