add throw for unmatched brackets

1 files changed, 6 insertions, 1 deletions

diff --git a/module-test/lexer_test.cc b/module-test/lexer_test.cc
index 50b6da0..20e9556 100644
--- a/module-test/lexer_test.cc
+++ b/module-test/lexer_test.cc
@@ -37,7 +37,7 @@ constexpr int MAXLINE = 1024;
 int main()
 {
     verbose = true;
-    int test_case = 16;
+    int test_case = 17;
     string s;
 
     switch (test_case)
@@ -121,6 +121,11 @@ int main()
             s = "(ls)";
             break;
 
+        // more LEFT brackets than RIGHT
+        case 17:
+            s = "((alpha)";
+            break;
+
         default:
             return 0;
     }