Handle negative numbers in print

tests/print_tests.c

@@ -50,6 +50,14 @@ static void test_integer_10(void)
 	TEST_ASSERT_EQUAL_MEMORY("10", buffer, 2);
 }
 
+static void test_integer_minus_4321(void)
+{
+	am.val = expr_integer(&am, -4321);
+	const size_t len = print(&am, buffer, BUFFER_SIZE);
+	TEST_ASSERT_EQUAL(5, len);
+	TEST_ASSERT_EQUAL_MEMORY("-4321", buffer, 5);
+}
+
 int main(void)
 {
 	UNITY_BEGIN();
@@ -57,5 +65,6 @@ int main(void)
 	RUN_TEST(test_integer_1234);
 	RUN_TEST(test_integer_0);
 	RUN_TEST(test_integer_10);
+	RUN_TEST(test_integer_minus_4321);
 	return UNITY_END();
 }