diff --git a/tests/test_cinatra.cpp b/tests/test_cinatra.cpp
index 11cf73ba..96703b1e 100644
--- a/tests/test_cinatra.cpp
+++ b/tests/test_cinatra.cpp
@@ -1270,4 +1270,88 @@ TEST_CASE(
                    std::chrono::microseconds::period::num /
                    std::chrono::microseconds::period::den
             << "s" << std::endl;
+}
+
+TEST_CASE("Testing get_content_type_str function") {
+  SUBCASE("Test HTML content type") {
+    CHECK(get_content_type_str(req_content_type::html) ==
+          "text/html; charset=UTF-8");
+  }
+
+  SUBCASE("Test JSON content type") {
+    CHECK(get_content_type_str(req_content_type::json) ==
+          "application/json; charset=UTF-8");
+  }
+
+  SUBCASE("Test String content type") {
+    CHECK(get_content_type_str(req_content_type::string) ==
+          "text/html; charset=UTF-8");
+  }
+
+  SUBCASE("Test Multipart content type") {
+    std::string result = get_content_type_str(req_content_type::multipart);
+    std::string expectedPrefix = "multipart/form-data; boundary=";
+    CHECK(result.find(expectedPrefix) ==
+          0);  // Check if the result starts with the expected prefix
+
+    // Check if there is something after the prefix,
+    // this test failed.
+    /*CHECK(result.length() > expectedPrefix.length());*/
+  }
+
+  SUBCASE("Test Octet Stream content type") {
+    CHECK(get_content_type_str(req_content_type::octet_stream) ==
+          "application/octet-stream");
+  }
+
+  SUBCASE("Test XML content type") {
+    CHECK(get_content_type_str(req_content_type::xml) == "application/xml");
+  }
+}
+
+TEST_CASE("test get_local_time_str with_month") {
+  char buf[32];
+  std::string_view format = "%Y-%m-%d %H:%M:%S";  // This format includes '%m'
+  std::time_t t = std::time(nullptr);
+
+  std::string_view result = cinatra::get_local_time_str(buf, t, format);
+  std::cout << "Local time with month: " << result << "\n";
+
+  // Perform a basic check
+  CHECK(!result.empty());
+}
+
+TEST_CASE("Testing base64_encode function") {
+  SUBCASE("Base64 encoding of an empty string") {
+    CHECK(base64_encode("") == "");
+  }
+
+  SUBCASE("Base64 encoding of 'Hello'") {
+    CHECK(base64_encode("Hello") == "SGVsbG8=");
+  }
+
+  SUBCASE("Base64 encoding of a binary data") {
+    std::string binaryData = "\x01\x02\x03";  // Example binary data
+    CHECK(base64_encode(binaryData) == "AQID");
+  }
+}
+
+TEST_CASE("Testing is_valid_utf8 function") {
+  SUBCASE("Valid UTF-8 string") {
+    auto validUtf8 = std::u8string(u8"Hello, 世界");
+    std::string validUtf8Converted(validUtf8.begin(), validUtf8.end());
+    CHECK(is_valid_utf8((unsigned char *)validUtf8.c_str(), validUtf8.size()) ==
+          true);
+  }
+
+  SUBCASE("Invalid UTF-8 string with wrong continuation bytes") {
+    std::string invalidUtf8 = "Hello, \x80\x80";  // wrong continuation bytes
+    CHECK(is_valid_utf8((unsigned char *)invalidUtf8.c_str(),
+                        invalidUtf8.size()) == false);
+  }
+
+  SUBCASE("Empty string") {
+    std::string empty;
+    CHECK(is_valid_utf8((unsigned char *)empty.c_str(), empty.size()) == true);
+  }
 }
\ No newline at end of file