Add extra tests, all passing

eth2/utils/tree_hash/src/cached_tree_hash/impls/vec.rs

@@ -5,7 +5,7 @@ where
     T: CachedTreeHash<T> + TreeHash,
 {
     fn new_tree_hash_cache(&self, depth: usize) -> Result<TreeHashCache, Error> {
-        let mut overlay = self.tree_hash_cache_overlay(0, depth)?;
+        let overlay = self.tree_hash_cache_overlay(0, depth)?;
 
         let mut cache = match T::tree_hash_type() {
             TreeHashType::Basic => TreeHashCache::from_bytes(

eth2/utils/tree_hash/src/cached_tree_hash/tree_hash_cache.rs

@@ -183,6 +183,7 @@ impl TreeHashCache {
             .iter()
             .skip(overlay_index)
             .position(|o| o.depth <= depth)
+            .and_then(|i| Some(i + overlay_index))
             .unwrap_or_else(|| self.overlays.len());
 
         self.overlays.splice(overlay_index..end, vec![]);

eth2/utils/tree_hash/tests/tests.rs

@@ -231,8 +231,7 @@ pub struct StructWithVecOfStructs {
     pub c: Vec<Inner>,
 }
 
-#[test]
-fn test_struct_with_vec_of_structs() {
+fn get_struct_with_vec_of_structs() -> Vec<StructWithVecOfStructs> {
     let inner_a = Inner {
         a: 12,
         b: 13,
@@ -285,21 +284,62 @@ fn test_struct_with_vec_of_structs() {
         ..a.clone()
     };
 
+    vec![a, b, c, d, e, f]
+}
+
+#[test]
+fn test_struct_with_vec_of_structs() {
+    let variants = get_struct_with_vec_of_structs();
+
+    test_routine(variants[0].clone(), variants.clone());
+    test_routine(variants[1].clone(), variants.clone());
+    test_routine(variants[2].clone(), variants.clone());
+    test_routine(variants[3].clone(), variants.clone());
+    test_routine(variants[4].clone(), variants.clone());
+    test_routine(variants[5].clone(), variants.clone());
+}
+
+#[derive(Clone, Debug, TreeHash, CachedTreeHash)]
+pub struct StructWithVecOfStructWithVecOfStructs {
+    pub a: Vec<StructWithVecOfStructs>,
+    pub b: u64,
+}
+
+#[test]
+fn test_struct_with_vec_of_struct_with_vec_of_structs() {
+    let structs = get_struct_with_vec_of_structs();
+
     let variants = vec![
-        a.clone(),
-        b.clone(),
-        c.clone(),
-        d.clone(),
-        e.clone(),
-        f.clone(),
+        StructWithVecOfStructWithVecOfStructs {
+            a: structs[..].to_vec(),
+            b: 99,
+        },
+        StructWithVecOfStructWithVecOfStructs { a: vec![], b: 99 },
+        StructWithVecOfStructWithVecOfStructs {
+            a: structs[0..2].to_vec(),
+            b: 99,
+        },
+        StructWithVecOfStructWithVecOfStructs {
+            a: structs[0..2].to_vec(),
+            b: 100,
+        },
+        StructWithVecOfStructWithVecOfStructs {
+            a: structs[0..1].to_vec(),
+            b: 100,
+        },
+        StructWithVecOfStructWithVecOfStructs {
+            a: structs[0..4].to_vec(),
+            b: 100,
+        },
+        StructWithVecOfStructWithVecOfStructs {
+            a: structs[0..5].to_vec(),
+            b: 8,
+        },
     ];
 
-    test_routine(a, variants.clone());
-    test_routine(b, variants.clone());
-    test_routine(c, variants.clone());
-    test_routine(d, variants.clone());
-    test_routine(e, variants.clone());
-    test_routine(f, variants);
+    for v in &variants {
+        test_routine(v.clone(), variants.clone());
+    }
 }
 
 #[derive(Clone, Debug, TreeHash, CachedTreeHash)]