diff --git a/libs/utils/src/approx_accurate.rs b/libs/utils/src/approx_accurate.rs
index 5de3461521..e7af36eec4 100644
--- a/libs/utils/src/approx_accurate.rs
+++ b/libs/utils/src/approx_accurate.rs
@@ -4,7 +4,7 @@
 /// If a single `None` value is merged, it becomes `Approximate` variant.
 ///
 /// Remove when `Layer::file_size` is no longer an `Option`.
-#[derive(Default, Debug)]
+#[derive(Default, Debug, Clone, Copy)]
 pub enum ApproxAccurate<T> {
     Approximate(T),
     Accurate(T),
@@ -49,3 +49,52 @@ impl<T: Ord + Copy + Default> ApproxAccurate<T> {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::ApproxAccurate;
+
+    #[test]
+    fn accumulate_only_some() {
+        let acc = (0..=5)
+            .into_iter()
+            .map(Some)
+            .fold(ApproxAccurate::default(), |acc, next| acc.max(next));
+
+        assert_eq!(acc.accurate(), Some(5));
+        assert!(!acc.is_approximate());
+        assert_eq!(acc.unwrap_accurate_or(42), 5);
+    }
+
+    #[test]
+    fn accumulate_some_and_none() {
+        let acc = [Some(0), None, Some(2)]
+            .into_iter()
+            .fold(ApproxAccurate::default(), |acc, next| acc.max(next));
+
+        assert_eq!(acc.accurate(), None);
+        assert!(acc.is_approximate());
+        assert_eq!(acc.unwrap_accurate_or(42), 42);
+    }
+
+    #[test]
+    fn accumulate_none_and_some() {
+        let acc = [None, Some(1), None]
+            .into_iter()
+            .fold(ApproxAccurate::default(), |acc, next| acc.max(next));
+
+        assert_eq!(acc.accurate(), None);
+        assert!(acc.is_approximate());
+        assert_eq!(acc.unwrap_accurate_or(42), 42);
+    }
+
+    #[test]
+    fn accumulate_none() {
+        let acc = ApproxAccurate::<i32>::default();
+
+        // it is accurate empty
+        assert_eq!(acc.accurate(), Some(0));
+        assert!(!acc.is_approximate());
+        assert_eq!(acc.unwrap_accurate_or(42), 0);
+    }
+}