Merge pull request #2647 from input-output-hk/djo/2580/refactor-common-dummies

refactor: rethink dummies test doubles

Author: Alenar

Cargo.lock

@@ -23,6 +23,34 @@ To complete
 To complete
 -->
 
+### 3. Guidelines for Dummy Test Doubles
+
+**Date:** 2025-07-22
+**Status:** Accepted
+
+#### Context
+
+The use of `dummy()` functions for creating test doubles is widespread across the codebase. However, inconsistencies
+in their placement and visibility have led to maintenance challenges and reduced code clarity.
+
+#### Decision
+
+A `Dummy` trait will be introduced, functioning similarly to Rust's `Default` trait.
+
+The following guidelines will be adopted for implementing the `Dummy` trait:
+
+1. Most implementations should reside in a `test::double::dummies` module within the crate where the type is defined.
+2. For types with non-public fields, the `Dummy` trait should be implemented directly below the type's definition.
+
+#### Consequences
+
+- Enhanced consistency in code organization.
+- Improved discoverability of test doubles.
+- Clearer distinction between production and test code.
+- Simplified maintenance of test implementations.
+
+---
+
 ## 2. Remove Artifacts serialization support when compiling to WebAssembly
 
 date: 2025-02-26

DEV-ADR.md

@@ -1,6 +1,6 @@
 [package]
 name = "mithril-cardano-node-chain"
-version = "0.1.4"
+version = "0.1.5"
 authors.workspace = true
 documentation.workspace = true
 edition.workspace = true

internal/cardano-node/mithril-cardano-node-chain/Cargo.toml

@@ -212,7 +212,7 @@ impl ChainObserver for FakeChainObserver {
 
 #[cfg(test)]
 mod tests {
-    use mithril_common::test_utils::fake_data;
+    use mithril_common::test_utils::{double::Dummy, fake_data};
 
     use super::*;
 

internal/cardano-node/mithril-cardano-node-chain/src/test/double/chain_observer.rs

@@ -1,7 +1,7 @@
 [package]
 name = "mithril-dmq"
 description = "Mechanisms to publish and consume messages of a 'Decentralized Message Queue network' through a DMQ node"
-version = "0.1.4"
+version = "0.1.5"
 authors.workspace = true
 documentation.workspace = true
 edition.workspace = true

internal/mithril-dmq/Cargo.toml

@@ -94,6 +94,7 @@ mod tests {
     use mithril_common::{
         crypto_helper::{KesSignerFake, TryToBytes},
         entities::{BlockNumber, ChainPoint, TimePoint},
+        test_utils::double::Dummy,
     };
 
     use super::*;

internal/mithril-dmq/src/message.rs

@@ -82,7 +82,6 @@ impl<M: TryToBytes + Debug + Sync + Send> DmqPublisher<M> for DmqPublisherPallas
 
 #[cfg(all(test, unix))]
 mod tests {
-
     use std::{fs, sync::Arc};
 
     use pallas_network::miniprotocols::{
@@ -91,7 +90,11 @@ mod tests {
     use tokio::{net::UnixListener, task::JoinHandle};
 
     use mithril_cardano_node_chain::test::double::FakeChainObserver;
-    use mithril_common::{crypto_helper::KesSignerFake, current_function, test_utils::TempDir};
+    use mithril_common::{
+        crypto_helper::KesSignerFake,
+        current_function,
+        test_utils::{TempDir, double::Dummy},
+    };
 
     use crate::{test::payload::DmqMessageTestPayload, test_tools::TestLogger};
 

internal/mithril-dmq/src/publisher/pallas.rs

@@ -3,6 +3,7 @@ use std::fmt::Debug;
 use mithril_common::{
     StdResult,
     crypto_helper::{TryFromBytes, TryToBytes},
+    test_utils::double::Dummy,
 };
 
 /// A test message payload for the DMQ.
@@ -18,9 +19,11 @@ impl DmqMessageTestPayload {
             message: bytes.to_vec(),
         }
     }
+}
 
+impl Dummy for DmqMessageTestPayload {
     /// Creates a dummy `DmqMessageTestPayload` with a predefined message.
-    pub fn dummy() -> Self {
+    fn dummy() -> Self {
         Self {
             message: b"dummy message".to_vec(),
         }

internal/mithril-dmq/src/test/payload.rs

@@ -1,6 +1,6 @@
 [package]
 name = "mithril-era"
-version = "0.1.2"
+version = "0.1.3"
 authors.workspace = true
 documentation.workspace = true
 edition.workspace = true

internal/mithril-era/Cargo.toml

@@ -22,6 +22,8 @@ impl EraReaderAdapter for BootstrapAdapter {
 
 #[cfg(test)]
 mod tests {
+    use mithril_common::test_utils::double::Dummy;
+
     use super::*;
 
     #[tokio::test]