Module flake_detector 

Anytime-Valid Flake Detector (bd-1plj).

Detects flaky timing regressions in E2E tests without inflating false positives, using anytime-valid e-process statistics.

Mathematical Model

For sub-Gaussian residuals r_t (mean 0 under null), the e-value at time t is:

e_t = exp(λ × r_t − (λ² × σ²) / 2)
E_t = ∏_{i=1}^t e_i

We reject H₀ (system is stable) when E_t > 1/α, providing anytime-valid Type I error control.

Key Properties

• Anytime-valid: Can stop testing early without invalid inference
• No false positives in stable runs: E[E_t] ≤ 1 under H₀
• Early detection: Strong evidence triggers early failure
• Variable-length support: Works with different test run lengths

Failure Modes

Condition	Behavior	Rationale
σ = 0	Clamp to σ_MIN	Division by zero guard
E_t underflow	Clamp to E_MIN	Prevents permanent zero-lock
E_t overflow	Clamp to E_MAX	Numerical stability
No observations	E_t = 1	Identity element

Example

use ftui_runtime::flake_detector::{FlakeDetector, FlakeConfig};

let mut detector = FlakeDetector::new(FlakeConfig::default());

// Observe latency deviations
let decision = detector.observe(latency_deviation);
if decision.is_flaky {
    eprintln!("Flaky test detected");
}

Structs

EvidenceLog

Log entry for evidence tracking.

FlakeConfig

Configuration for the flake detector.

FlakeDecision

Decision returned by the flake detector.

FlakeDetector

Anytime-valid flake detector using e-process statistics.

FlakeSummary

Summary of flake detection run.