Add unit tests to raise coverage score

Signed-off-by: YUAN LYU <lyuyuan92@gmail.com>

src/common/headers.rs

@@ -432,6 +432,7 @@ mod tests {
         assert_eq!(headers.content_length(), 0);
         assert_eq!(headers.chunked(), false);
         assert_eq!(headers.expect(), false);
+        assert_eq!(headers.accept(), MediaType::PlainText);
     }
 
     #[test]
@@ -726,4 +727,13 @@ mod tests {
         let header = Header::try_from(b"Accept").unwrap();
         assert_eq!(header.raw(), b"Accept");
     }
+
+    #[test]
+    fn test_set_accept() {
+        let mut headers = Headers::default();
+        assert_eq!(headers.accept(), MediaType::PlainText);
+
+        headers.set_accept(MediaType::ApplicationJson);
+        assert_eq!(headers.accept(), MediaType::ApplicationJson);
+    }
 }

src/common/mod.rs

@@ -522,6 +522,14 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_display_route_error() {
+        assert_eq!(
+            format!("{}", RouteError::HandlerExist("test".to_string())),
+            "handler for test already exists"
+        );
+    }
+
     #[test]
     fn test_method_to_str() {
         let val = Method::Get;

src/response.rs

@@ -383,4 +383,15 @@ mod tests {
         response.allow_method(Method::Put);
         assert_eq!(response.allow(), vec![Method::Get, Method::Put]);
     }
+
+    #[test]
+    fn test_equal() {
+        let response = Response::new(Version::Http10, StatusCode::MethodNotAllowed);
+        let another_response = Response::new(Version::Http10, StatusCode::MethodNotAllowed);
+        assert_eq!(response, another_response);
+
+        let response = Response::new(Version::Http10, StatusCode::OK);
+        let another_response = Response::new(Version::Http10, StatusCode::BadRequest);
+        assert_ne!(response, another_response);
+    }
 }