Added serde feature flags to tests

src/algorithm/neighbour/cover_tree.rs

@@ -457,7 +457,8 @@ mod tests {
     use super::*;
     use crate::math::distance::Distances;
 
-    #[derive(Debug, Serialize, Deserialize, Clone)]
+    #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+    #[derive(Debug, Clone)]
     struct SimpleDistance {}
 
     impl Distance<i32, f64> for SimpleDistance {
@@ -503,6 +504,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg(feature = "serde")]
     fn serde() {
         let data = vec![1, 2, 3, 4, 5, 6, 7, 8, 9];
 

src/algorithm/neighbour/linear_search.rs

@@ -140,7 +140,8 @@ mod tests {
     use super::*;
     use crate::math::distance::Distances;
 
-    #[derive(Debug, Serialize, Deserialize, Clone)]
+    #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+    #[derive(Debug, Clone)]
     struct SimpleDistance {}
 
     impl Distance<i32, f64> for SimpleDistance {