feat(aggregator): implement a 'SignatureConsumerNoop' for 'SignatureConsumer' trait

Author: jpraynaud

mithril-aggregator/src/services/signature_consumer/noop.rs

@@ -0,0 +1,43 @@
+use std::future;
+
+use async_trait::async_trait;
+
+use super::SignatureConsumer;
+
+/// A no-op implementation of the [SignatureConsumer] trait that will never return signatures.
+#[derive(Default)]
+pub struct SignatureConsumerNoop;
+
+#[async_trait]
+impl SignatureConsumer for SignatureConsumerNoop {
+    async fn get_signatures(
+        &self,
+    ) -> mithril_common::StdResult<
+        Vec<(
+            mithril_common::entities::SingleSignature,
+            mithril_common::entities::SignedEntityType,
+        )>,
+    > {
+        future::pending().await
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use anyhow::anyhow;
+    use tokio::time::{sleep, Duration};
+
+    use super::*;
+
+    #[tokio::test]
+    async fn signature_consumer_noop_never_returns() {
+        let consumer = SignatureConsumerNoop;
+
+        let result = tokio::select!(
+            _res = sleep(Duration::from_millis(100)) => {Err(anyhow!("Timeout"))},
+            _res =  consumer.get_signatures()  => {Ok(())},
+        );
+
+        result.expect_err("Should have timed out");
+    }
+}