diff --git a/chain/ethereum/src/chain.rs b/chain/ethereum/src/chain.rs
index 9b7c3e8b3f0..24486f9cf3a 100644
--- a/chain/ethereum/src/chain.rs
+++ b/chain/ethereum/src/chain.rs
@@ -790,6 +790,32 @@ async fn fetch_unique_blocks_from_cache(
     (blocks, missing_blocks)
 }
 
+/// Fetches blocks by their numbers, first attempting to load from cache.
+/// Missing blocks are retrieved from an external source, with all blocks sorted and converted to `BlockFinality` format.
+async fn load_blocks<F, Fut>(
+    logger: &Logger,
+    chain_store: Arc<dyn ChainStore>,
+    block_numbers: HashSet<BlockNumber>,
+    fetch_missing: F,
+) -> Result<Vec<BlockFinality>>
+where
+    F: FnOnce(Vec<BlockNumber>) -> Fut,
+    Fut: Future<Output = Result<Vec<Arc<ExtendedBlockPtr>>>>,
+{
+    // Fetch cached blocks and identify missing ones
+    let (mut cached_blocks, missing_block_numbers) =
+        fetch_unique_blocks_from_cache(logger, chain_store, block_numbers).await;
+
+    // Fetch missing blocks if any
+    if !missing_block_numbers.is_empty() {
+        let missing_blocks = fetch_missing(missing_block_numbers).await?;
+        cached_blocks.extend(missing_blocks);
+        cached_blocks.sort_by_key(|block| block.number);
+    }
+
+    Ok(cached_blocks.into_iter().map(BlockFinality::Ptr).collect())
+}
+
 #[async_trait]
 impl TriggersAdapterTrait<Chain> for TriggersAdapter {
     async fn scan_triggers(
@@ -819,32 +845,6 @@ impl TriggersAdapterTrait<Chain> for TriggersAdapter {
         logger: Logger,
         block_numbers: HashSet<BlockNumber>,
     ) -> Result<Vec<BlockFinality>> {
-        // Common function to handle block loading, regardless of source
-        async fn load_blocks<F, Fut>(
-            logger: &Logger,
-            chain_store: Arc<dyn ChainStore>,
-            block_numbers: HashSet<BlockNumber>,
-            fetch_missing: F,
-        ) -> Result<Vec<BlockFinality>>
-        where
-            F: FnOnce(Vec<BlockNumber>) -> Fut,
-            Fut: Future<Output = Result<Vec<Arc<ExtendedBlockPtr>>>>,
-        {
-            // Fetch cached blocks and identify missing ones
-            let (mut cached_blocks, missing_block_numbers) =
-                fetch_unique_blocks_from_cache(logger, chain_store, block_numbers).await;
-
-            // Fetch missing blocks if any
-            if !missing_block_numbers.is_empty() {
-                let missing_blocks = fetch_missing(missing_block_numbers).await?;
-                cached_blocks.extend(missing_blocks);
-                cached_blocks.sort_by_key(|block| block.number);
-            }
-
-            // Convert to BlockFinality
-            Ok(cached_blocks.into_iter().map(BlockFinality::Ptr).collect())
-        }
-
         match &*self.chain_client {
             ChainClient::Firehose(endpoints) => {
                 trace!(
@@ -1193,3 +1193,138 @@ impl FirehoseMapperTrait<Chain> for FirehoseMapper {
             .await
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use graph::blockchain::mock::MockChainStore;
+    use graph::{slog, tokio};
+
+    use super::*;
+    use std::collections::HashSet;
+    use std::sync::Arc;
+
+    // Helper function to create test blocks
+    fn create_test_block(number: BlockNumber, hash: &str) -> ExtendedBlockPtr {
+        let hash = BlockHash(hash.as_bytes().to_vec().into_boxed_slice());
+        let ptr = BlockPtr::new(hash.clone(), number);
+        ExtendedBlockPtr {
+            hash,
+            number,
+            parent_hash: BlockHash(vec![0; 32].into_boxed_slice()),
+            timestamp: BlockTime::for_test(&ptr),
+        }
+    }
+
+    #[tokio::test]
+    async fn test_fetch_unique_blocks_single_block() {
+        let logger = Logger::root(slog::Discard, o!());
+        let mut chain_store = MockChainStore::default();
+
+        // Add a single block
+        let block = create_test_block(1, "block1");
+        chain_store.blocks.insert(1, vec![block.clone()]);
+
+        let block_numbers: HashSet<_> = vec![1].into_iter().collect();
+
+        let (blocks, missing) =
+            fetch_unique_blocks_from_cache(&logger, Arc::new(chain_store), block_numbers).await;
+
+        assert_eq!(blocks.len(), 1);
+        assert_eq!(blocks[0].number, 1);
+        assert!(missing.is_empty());
+    }
+
+    #[tokio::test]
+    async fn test_fetch_unique_blocks_duplicate_blocks() {
+        let logger = Logger::root(slog::Discard, o!());
+        let mut chain_store = MockChainStore::default();
+
+        // Add multiple blocks for the same number
+        let block1 = create_test_block(1, "block1a");
+        let block2 = create_test_block(1, "block1b");
+        chain_store
+            .blocks
+            .insert(1, vec![block1.clone(), block2.clone()]);
+
+        let block_numbers: HashSet<_> = vec![1].into_iter().collect();
+
+        let (blocks, missing) =
+            fetch_unique_blocks_from_cache(&logger, Arc::new(chain_store), block_numbers).await;
+
+        // Should filter out the duplicate block
+        assert!(blocks.is_empty());
+        assert_eq!(missing, vec![1]);
+        assert_eq!(missing[0], 1);
+    }
+
+    #[tokio::test]
+    async fn test_fetch_unique_blocks_missing_blocks() {
+        let logger = Logger::root(slog::Discard, o!());
+        let mut chain_store = MockChainStore::default();
+
+        // Add block number 1 but not 2
+        let block = create_test_block(1, "block1");
+        chain_store.blocks.insert(1, vec![block.clone()]);
+
+        let block_numbers: HashSet<_> = vec![1, 2].into_iter().collect();
+
+        let (blocks, missing) =
+            fetch_unique_blocks_from_cache(&logger, Arc::new(chain_store), block_numbers).await;
+
+        assert_eq!(blocks.len(), 1);
+        assert_eq!(blocks[0].number, 1);
+        assert_eq!(missing, vec![2]);
+    }
+
+    #[tokio::test]
+    async fn test_fetch_unique_blocks_multiple_valid_blocks() {
+        let logger = Logger::root(slog::Discard, o!());
+        let mut chain_store = MockChainStore::default();
+
+        // Add multiple valid blocks
+        let block1 = create_test_block(1, "block1");
+        let block2 = create_test_block(2, "block2");
+        chain_store.blocks.insert(1, vec![block1.clone()]);
+        chain_store.blocks.insert(2, vec![block2.clone()]);
+
+        let block_numbers: HashSet<_> = vec![1, 2].into_iter().collect();
+
+        let (blocks, missing) =
+            fetch_unique_blocks_from_cache(&logger, Arc::new(chain_store), block_numbers).await;
+
+        assert_eq!(blocks.len(), 2);
+        assert!(blocks.iter().any(|b| b.number == 1));
+        assert!(blocks.iter().any(|b| b.number == 2));
+        assert!(missing.is_empty());
+    }
+
+    #[tokio::test]
+    async fn test_fetch_unique_blocks_mixed_scenario() {
+        let logger = Logger::root(slog::Discard, o!());
+        let mut chain_store = MockChainStore::default();
+
+        // Add a mix of scenarios:
+        // - Block 1: Single valid block
+        // - Block 2: Multiple blocks (duplicate)
+        // - Block 3: Missing
+        let block1 = create_test_block(1, "block1");
+        let block2a = create_test_block(2, "block2a");
+        let block2b = create_test_block(2, "block2b");
+
+        chain_store.blocks.insert(1, vec![block1.clone()]);
+        chain_store
+            .blocks
+            .insert(2, vec![block2a.clone(), block2b.clone()]);
+
+        let block_numbers: HashSet<_> = vec![1, 2, 3].into_iter().collect();
+
+        let (blocks, missing) =
+            fetch_unique_blocks_from_cache(&logger, Arc::new(chain_store), block_numbers).await;
+
+        assert_eq!(blocks.len(), 1);
+        assert_eq!(blocks[0].number, 1);
+        assert_eq!(missing.len(), 2);
+        assert!(missing.contains(&2));
+        assert!(missing.contains(&3));
+    }
+}