Add tests around quantifiers to ensure both matching and non-matching compliance.

tests/test-grammar-integration.cpp

@@ -153,6 +153,115 @@ ws ::= [ \t\n\r]?)""";
     llama_grammar_free(grammar);
 }
 
+static void test_quantifiers() {
+    // Populate test data with grammar strings and their associated collections of expected passing and failing strings
+    const std::vector<
+        std::tuple<
+            std::string,
+            std::vector<std::string>,
+            std::vector<std::string>>>
+        test_data = {
+        {
+            // Grammar
+            R"""(root ::= "a"*)""",
+            // Passing strings
+            {
+                "",
+                "a",
+                "aaaaa",
+                "aaaaaaaaaaaaaaaaaa",
+                "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+            },
+            // Failing strings
+            {
+                "b",
+                "ab",
+                "aab",
+                "ba",
+                "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaab"
+            }
+        },
+        {
+            // Grammar
+            R"""(root ::= "a"+)""",
+            // Passing strings
+            {
+                "a",
+                "aaaaa",
+                "aaaaaaaaaaaaaaaaaa",
+                "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+            },
+            // Failing strings
+            {
+                "",
+                "b",
+                "ab",
+                "aab",
+                "ba",
+                "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaab"
+            }
+        },
+        {
+            // Grammar
+            R"""(root ::= "a"?)""",
+            // Passing strings
+            {
+                "",
+                "a"
+            },
+            // Failing strings
+            {
+                "b",
+                "ab",
+                "aa",
+                "ba",
+            }
+        }
+    };
+
+    for (const auto & test_datum : test_data) {
+        const auto & [grammar_str, passing_strings, failing_strings] = test_datum;
+
+        auto grammar = build_grammar(grammar_str);
+
+        // Save the original grammar stacks so that we can reset after every new string we want to test
+        auto original_stacks = grammar->stacks;
+
+        // Passing strings
+        for (const auto & test_string : passing_strings) {
+            bool matched = match_string(test_string, grammar);
+
+            if (!matched) {
+                fprintf(stderr, "Against grammar: %s\n", grammar_str.c_str());
+                fprintf(stderr, "Failed to match string: %s\n", test_string.c_str());
+            }
+
+            assert(matched);
+
+            // Reset the grammar stacks
+            grammar->stacks = original_stacks;
+        }
+
+        // Failing strings
+        for (const auto & test_string : failing_strings) {
+            bool matched = match_string(test_string, grammar);
+
+            if (matched) {
+                fprintf(stderr, "Against grammar: %s\n", grammar_str.c_str());
+                fprintf(stderr, "Improperly matched string: %s\n", test_string.c_str());
+            }
+
+            assert(!matched);
+
+            // Reset the grammar stacks
+            grammar->stacks = original_stacks;
+        }
+
+        // Clean up allocated memory
+        llama_grammar_free(grammar);
+    }
+}
+
 static void test_failure_missing_root() {
     // Test case for a grammar that is missing a root rule
     const std::string grammar_str = R"""(rot ::= expr
@@ -189,6 +298,7 @@ number ::= [0-9]+)""";
 int main() {
     test_simple_grammar();
     test_complex_grammar();
+    test_quantifiers();
     test_failure_missing_root();
     test_failure_missing_reference();
     fprintf(stdout, "All tests passed.\n");