diff --git a/src/headers.rs b/src/headers.rs
index 20ef6e8..ead2c94 100644
--- a/src/headers.rs
+++ b/src/headers.rs
@@ -14,7 +14,7 @@ pub fn get_header_value(request: &Request, value: String) -> String {
 
 
 pub fn get_header_user_agent(request: &Request) -> String {
-    return get_header_value("User-Agent");
+    return get_header_value(request, "User-Agent");
 }
 
 pub fn get_header_cookies(request: &Request) -> String {
@@ -38,3 +38,45 @@ pub fn get_header_cookies(request: &Request) -> String {
 
     return to_string(&cookies).unwrap();
 }
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use lambda_http::http::header::{HeaderMap, HeaderValue};
+    use lambda_http::{Body, Request};
+
+    fn mock_request(headers: Vec<(&str, &str)>) -> Request {
+        let mut header_map = HeaderMap::new();
+        for (key, value) in headers {
+            header_map.insert(key, HeaderValue::from_static(value));
+        }
+
+        Request::new(Body::Empty).with_headers(header_map)
+    }
+
+    #[test]
+    fn test_get_header_value_known() {
+        let request = mock_request(vec![("User-Agent", "TestAgent")]);
+        assert_eq!(get_header_value(&request, "User-Agent".to_string()), "TestAgent");
+    }
+
+    #[test]
+    fn test_get_header_value_unknown() {
+        let request = mock_request(vec![]);
+        assert_eq!(get_header_value(&request, "User-Agent".to_string()), "Unknown header value");
+    }
+
+    #[test]
+    fn test_get_header_user_agent() {
+        let request = mock_request(vec![("User-Agent", "TestAgent")]);
+        assert_eq!(get_header_user_agent(&request), "TestAgent");
+    }
+
+    #[test]
+    fn test_get_header_cookies() {
+        let request = mock_request(vec![("Cookie", "username=user; session=token")]);
+        assert_eq!(get_header_cookies(&request), r#"{"session":"token","username":"user"}"#);
+    }
+}
+