Add time slice fairness test

[leynos]

Summary

• add test to cover time-based queue fairness when max_high_before_low is zero
• add missing test for disabled fairness and annotate it properly
• clean up duplicate imports in test module
• use Tokio's virtual time to avoid flakiness in time slice fairness test
• move Tokio's test utilities to dev dependencies
• document enabling tokio's test-util feature for deterministic tests

Testing

• make fmt
• make lint
• make test
• cargo test --test connection_actor fairness_yields_low_with_time_slice -- --exact --nocapture

---

https://chatgpt.com/codex/tasks/task_e_68684cd037548322a494feb0d1e8476d

Summary by Sourcery

Add comprehensive fairness tests for connection queues, use Tokio virtual time for deterministic scheduling, reorganize dependencies, and update documentation for test utilities

Build:

• Move Tokio's test-util feature into dev-dependencies in Cargo.toml

Documentation:

• Document enabling Tokio's test-util feature for deterministic tests

Tests:

• Add disabled-fairness test when max_high_before_low is zero
• Add time-slice fairness test using Tokio's virtual time to avoid flakiness
• Clean up duplicate imports in the test module

[sourcery-ai]

Reviewer's Guide

This PR introduces two new asynchronous tests for queue fairness under disabled and time-slice configurations using Tokio's virtual time, cleans up duplicate test imports, and enables/documentation for Tokio's test utilities via a dev-only dependency.

Class diagram for new and updated test utilities usage

classDiagram
    class ConnectionActorTestModule {
        +fairness_yields_low_with_time_slice()
        +fairness_disabled()
        <<test>>
    }
    class TokioTestUtil {
        +pause()
        +advance()
        <<test-util>>
    }
    ConnectionActorTestModule ..> TokioTestUtil : uses

Loading

File-Level Changes

Change	Details	Files
Add disabled and time-slice fairness tests	Add disabled fairness test for zero max_high_before_low Add time-slice fairness test using Tokio’s virtual clock Annotate both tests with rstest and #[tokio::test]	tests/connection_actor.rs
Cleanup duplicate imports in tests	Remove redundant import statements in test module	tests/connection_actor.rs
Enable and document Tokio test utilities	Move tokio with test-util feature into dev-dependencies Document enabling tokio’s test-util feature in documentation	Cargo.toml docs/rust-testing-with-rstest-fixtures.md

---

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[coderabbitai]

Summary by CodeRabbit

• New Features

  • Introduced a new asynchronous test to verify fairness behaviour in connection handling with specific time slice and priority configurations.

• Documentation

  • Added guidance on enabling Tokio test utilities for use with rstest, including configuration instructions.

• Chores

  • Updated development dependencies to include Tokio with test utilities enabled for improved testing support.

Walkthrough

This update adds Tokio as a dev-dependency with test utilities enabled, enhances documentation with guidance on enabling Tokio test features for rstest, and introduces a new asynchronous test verifying fairness behaviour in ConnectionActor using Tokio's paused clock.

Changes

Files	Change Summary
Cargo.toml	Added Tokio crate as a dev-dependency with test-util feature enabled and default features off.
docs/rust-testing-with-rstest-fixtures.md	Added instructions for enabling Tokio test utilities in rstest by configuring Cargo.toml.
tests/connection_actor.rs	Added async test fairness_yields_low_with_time_slice using Tokio's paused clock; updated imports.

Possibly related issues

• Add test for time_slice-based fairness yielding in queue system #150: This issue requests an async test verifying fairness yielding behaviour with a time slice, which matches the new test added in this PR.

Possibly related PRs

• Add fairness counter for low-priority queue #145: Adds async tests for fairness behaviour in ConnectionActor, closely related to the new fairness test here.
• Add fairness disabled test #176: Adds async tests for fairness configurations in ConnectionActor, complementing the test added in this PR.
• Implement connection actor with prioritised write loop #129: Introduces initial ConnectionActor implementation and tests; this PR builds upon that foundation with additional fairness testing.

Summary by CodeRabbit

• New Features

  • Introduced two new asynchronous tests to verify fairness configurations in connection handling, ensuring correct prioritisation of high and low-priority frames.

• Documentation

  • Added guidance on enabling Tokio's test utilities for use with rstest, including configuration instructions.

• Chores

  • Updated development dependencies to include Tokio with test utilities enabled for improved testing support.

Poem

🐇 In code's swift race, I pause the clock,
With Tokio's help, I set the block.
Fairness tested, frames in line,
Low and high, they intertwine.
Dev-deps tuned, docs now bright,
Hop along, the tests take flight! 🌸🐰

---

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• Cargo.toml (1 hunks)
• tests/connection_actor.rs (2 hunks)

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🔇 Additional comments (3)

Cargo.toml (1)

25-25: Excellent addition for deterministic testing.

The tokio dev-dependency with test-util feature enabled is properly configured for virtual time testing. The explicit version range and minimal feature set follow best practices.

tests/connection_actor.rs (2)

8-11: Clean import organisation.

The addition of sync::oneshot is minimal and necessary for the new test. The import structure remains well-organised.

---

107-149: Excellent deterministic test implementation.

This test demonstrates best practices for async testing:

• Uses Tokio's virtual time for deterministic behaviour
• Clear documentation explaining the virtual time usage
• Proper task spawning with oneshot channel communication
• Logical timing sequence that exceeds the time slice threshold
• Comprehensive assertions verifying both presence and position of the low-priority frame

The test logic correctly verifies that time-based fairness yields low-priority frames when the time slice is exceeded, even with max_high_before_low: 0.

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[codescene-delta-analysis]

Gates Passed
6 Quality Gates Passed

See analysis details in CodeScene

Quality Gate Profile: Pay Down Tech Debt
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[sourcery-ai]

Hey @leynos - I've reviewed your changes - here's some feedback:

• Move the Tokio test‐util dependency into [dev-dependencies] in Cargo.toml (instead of main dependencies) to match the docs and avoid shipping test-only features.
• In fairness_yields_low_with_time_slice, consider tightening the assertion by checking the exact sequence or at least the relative ordering of high-priority items around the low-priority one for stronger determinism.
• Extract the common actor setup/run logic in the new fairness tests into a shared helper or fixture to reduce duplication and improve readability.

Prompt for AI Agents

Please address the comments from this code review:
## Overall Comments
- Move the Tokio test‐util dependency into `[dev-dependencies]` in Cargo.toml (instead of main dependencies) to match the docs and avoid shipping test-only features.
- In `fairness_yields_low_with_time_slice`, consider tightening the assertion by checking the exact sequence or at least the relative ordering of high-priority items around the low-priority one for stronger determinism.
- Extract the common actor setup/run logic in the new fairness tests into a shared helper or fixture to reduce duplication and improve readability.

---

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[codescene-delta-analysis]

Gates Passed
6 Quality Gates Passed

See analysis details in CodeScene

Quality Gate Profile: Pay Down Tech Debt
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