test(foundation): add examples and unit tests for InMemoryStorage search and history

[ashum9]

Summary

Enhances the test coverage for the InMemoryStorage component by adding asynchronous unit tests for its search, history, and statistics capabilities. Additionally, this PR introduces a runnable example to demonstrate these features in practice.

Part of the pre-GSoC testing series:

• PR test(foundation): add unit tests for InMemoryStorage basic operations #1220 — InMemoryStorage basic CRUD operations (depends on this being merged first)
• PR test(foundation): add examples and unit tests for InMemoryStorage search and history #1221 (this PR) — InMemoryStorage search, history, and stats + runnable example
• PR test(foundation): add comprehensive unit tests for Memory storage implementations #1284 — FileBasedStorage persistence, clear, and concurrency

Changes

• Search tests (test_in_memory_search): verifies keyword searching across stored documents, correct handling of limits, and non-matching queries including key-level assertions.
• History & stats tests (test_in_memory_history_and_stats): validates Message history tracking, stats accuracy (total messages, sessions, items), and correct clear() vs clear_history() semantics.
• Runnable example (examples/memory_history_search.rs): complete demo showcasing how to initialize InMemoryStorage, interact with conversational history, store data, and execute keyword searches.

Motivation

Proper search and history tracking are essential features for building complex agent applications. These tests ensure the reliability of these advanced memory operations. The new example provides a practical reference for developers integrating InMemoryStorage into their own workflows.

cc @amosli @BH3GEI

[Copilot]

Pull request overview

This PR improves the reliability and usability of InMemoryStorage in mofa-foundation by adding async unit tests for search/history/stats behavior and introducing a runnable example demonstrating those APIs.

Changes:

• Added async unit tests for InMemoryStorage keyword search (including limit/non-match cases).
• Added async unit tests for history tracking and stats reporting (including clear vs clear_history scenarios).
• Added an example program demonstrating storing items, adding conversation history, and running keyword search.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
crates/mofa-foundation/src/agent/components/memory.rs	Adds tokio::test coverage for InMemoryStorage search/history/stats behavior.
crates/mofa-foundation/examples/memory_history_search.rs	Adds a runnable demo showcasing history + keyword search usage with InMemoryStorage.

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