Add massa execution worker unit test documentation + mention of massa…

…-unit-test-src repo (#4855)

massa-execution-worker/src/tests/mod.rs

@@ -1,5 +1,31 @@
 // Copyright (c) 2022 MASSA LABS <[email protected]>
 
+//! # General description
+//!
+//! Unit tests for the massa-execution-worker crate
+//!
+//! # Hierarchy
+//!
+//! ## interface
+//!
+//! Unit tests checking for ABI implementation.
+//!
+//! ## tests_active_history.rs
+//!
+//! Unit tests for the ActiveHistory struct.
+//!
+//! ## scenarios_mandatories.rs
+//!
+//! Complex unit tests using mocks for some parts of the massa node. See universe.rs for more information
+//! about the testing framework.
+//!
+//! # Wasm source code
+//!
+//! A lot of unit tests requires to deploy some very simple smart contract (ABI tests, SC limit tests...).
+//!
+//! You can find the wasm source code in the [massa-unit-test-src repository](https://github.com/massalabs/massa-unit-tests-src)
+//! and easily modify / compile them.
+
 #[cfg(test)]
 mod scenarios_mandatories;