Project 18: Reliability Test Harness (Unity, HIL, Fuzzing, Soak Tests)

Build a complete firmware reliability system that combines target unit tests, host fuzzing, hardware-in-the-loop automation, and long-run soak testing.

Quick Reference

Attribute Value
Difficulty Expert
Time Estimate 2-3 weeks
Main Programming Language C
Alternative Programming Languages C++, Python (test orchestration)
Coolness Level Level 4
Business Potential Level 5
Prerequisites Testing fundamentals, parser robustness basics
Key Topics Unity tests, HIL scripting, fuzzing, leak detection, soak methodology

1. Learning Objectives

  1. Build a reliable embedded test pyramid.
  2. Automate hardware interaction and fault injection.
  3. Fuzz packet and storage parsers safely.
  4. Detect leaks and stability drift in long runs.

2. Theory

2.1 Reliability is a System

Quality emerges from layered tests and fast feedback loops, not from one giant test stage.

2.2 Failure Reproduction Discipline

A failure without deterministic reproduction steps is not debug-ready.

3. Specification

  • Target unit tests using ESP-IDF Unity support.
  • HIL harness for keyboard and SD workflows.
  • Fuzz campaigns for packet/file parsers.
  • 24-hour soak with health telemetry.

Output:

[unit] PASS 128
[fuzz] PASS 12000 cases
[hil] PASS keyboard automation
[soak] PASS 24h resets=0 leak_slope=+0.2KB/h

4. Architecture

[Test Orchestrator] -> [Unit Runner]
                    -> [Host Fuzzer]
                    -> [HIL Controller]
                    -> [Soak Monitor]

5. Implementation Guide

Core question:

“How do I prove this firmware remains stable under both normal and adversarial inputs?”

Design questions:

  1. Which tests gate every commit?
  2. Which failures block release immediately?
  3. Which metrics indicate memory leak onset?

6. Testing Strategy

  • Commit-level: fast unit and parser tests.
  • Nightly: HIL and fuzz regressions.
  • Weekly: soak and trend analysis.

7. Pitfalls

  • Over-reliance on unit tests without hardware realism.
  • Fuzzing without crash triage strategy.
  • Soak logs too sparse for root-cause analysis.

8. Extensions

  • Add mutation corpus minimization.
  • Add flaky-test quarantine and auto-retry reporting.

9. Completion

  • Reliability suite runs from one command.
  • Failures are reproducible with clear artifacts.
  • Soak metrics show stable long-run behavior.