What is condition-wait?

This Claude skill optimizes automated testing by replacing unreliable arbitrary timeouts with robust condition-based polling. It is specifically designed to eliminate flaky tests caused by race conditions and timing dependencies, ensuring consistent test results across different environments and CI/CD pipelines while significantly reducing overall execution time.

When should I use condition-wait?

condition-wait is useful in the following scenarios: • Eliminating flaky tests that pass on local machines but fail under load or in CI/CD environments due to timing guesses. • Replacing hardcoded sleep or setTimeout calls with dynamic polling to wait for specific UI states, API responses, or database changes. • Synchronizing asynchronous operations in integration tests to ensure assertions only run after the system reaches the required state. • Improving test suite performance by removing unnecessary wait times and proceeding immediately once a condition is met. • Handling file system or resource availability checks where the timing of creation or modification is unpredictable.

name	condition-wait
description	Use when tests have race conditions, timing dependencies, or inconsistent pass/fail behavior - replaces arbitrary timeouts with condition polling to wait for actual state changes, eliminating flaky tests from timing guesses
allowed-tools	Bash(pytest:*), Read

Condition-Based Waiting

Overview

Flaky tests often guess at timing with arbitrary delays. This creates race conditions where tests pass on fast machines but fail under load or in CI.

Core principle: Wait for the actual condition you care about, not a guess about how long it takes.

When to Use

digraph when_to_use {
    "Test uses setTimeout/sleep?" [shape=diamond];
    "Testing timing behavior?" [shape=diamond];
    "Document WHY timeout needed" [shape=box];
    "Use condition-based waiting" [shape=box];

    "Test uses setTimeout/sleep?" -> "Testing timing behavior?" [label="yes"];
    "Testing timing behavior?" -> "Document WHY timeout needed" [label="yes"];
    "Testing timing behavior?" -> "Use condition-based waiting" [label="no"];
}

Use when:

Tests have arbitrary delays (setTimeout, sleep, time.sleep())
Tests are flaky (pass sometimes, fail under load)
Tests timeout when run in parallel
Waiting for async operations to complete

Don't use when:

Testing actual timing behavior (debounce, throttle intervals)
Always document WHY if using arbitrary timeout

Core Pattern

// ❌ BEFORE: Guessing at timing
await new Promise(r => setTimeout(r, 50));
const result = getResult();
expect(result).toBeDefined();

// ✅ AFTER: Waiting for condition
await waitFor(() => getResult() !== undefined);
const result = getResult();
expect(result).toBeDefined();

Quick Patterns

Scenario	Pattern
Wait for event	`waitFor(() => events.find(e => e.type === 'DONE'))`
Wait for state	`waitFor(() => machine.state === 'ready')`
Wait for count	`waitFor(() => items.length >= 5)`
Wait for file	`waitFor(() => fs.existsSync(path))`
Complex condition	`waitFor(() => obj.ready && obj.value > 10)`

Implementation

Generic polling function:

async function waitFor<T>(
  condition: () => T | undefined | null | false,
  description: string,
  timeoutMs = 5000
): Promise<T> {
  const startTime = Date.now();

  while (true) {
    const result = condition();
    if (result) return result;

    if (Date.now() - startTime > timeoutMs) {
      throw new Error(`Timeout waiting for ${description} after ${timeoutMs}ms`);
    }

    await new Promise(r => setTimeout(r, 10)); // Poll every 10ms
  }
}

See @example.ts for complete implementation with domain-specific helpers (waitForEvent, waitForEventCount, waitForEventMatch) from actual debugging session.

Common Mistakes

❌ Polling too fast: setTimeout(check, 1) - wastes CPU ✅ Fix: Poll every 10ms

❌ No timeout: Loop forever if condition never met ✅ Fix: Always include timeout with clear error

❌ Stale data: Cache state before loop ✅ Fix: Call getter inside loop for fresh data

When Arbitrary Timeout IS Correct

// Tool ticks every 100ms - need 2 ticks to verify partial output
await waitForEvent(manager, 'TOOL_STARTED'); // First: wait for condition
await new Promise(r => setTimeout(r, 200));   // Then: wait for timed behavior
// 200ms = 2 ticks at 100ms intervals - documented and justified

Requirements:

First wait for triggering condition
Based on known timing (not guessing)
Comment explaining WHY

Real-World Impact

From debugging session (2025-10-03):

Fixed 15 flaky tests across 3 files
Pass rate: 60% → 100%
Execution time: 40% faster
No more race conditions

condition-wait

When & Why to Use This Skill

Use Cases