Agent skill

condition-based-waiting

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

View SKILL.md on GitHub Repository
Stars 0
Forks 1

Install this agent skill to your Project

npx add-skill https://github.com/nimeshgurung/artifact-hub-collections/tree/main/skills/raw/obra/superpowers/skills/condition-based-waiting

SKILL.md

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

dot
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

typescript
// ❌ 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:

typescript
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

typescript
// 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:

  1. First wait for triggering condition
  2. Based on known timing (not guessing)
  3. 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

Recommended Agent Skills

Expand your agent's capabilities with these related and highly-rated skills.

nimeshgurung/artifact-hub-collections

internal-comms

A set of resources to help me write all kinds of internal communications, using the formats that my company likes to use. Claude should use this skill whenever asked to write some sort of internal communications (status reports, leadership updates, 3P updates, company newsletters, FAQs, incident reports, project updates, etc.).

0 1
Explore
nimeshgurung/artifact-hub-collections

mcp-builder

Guide for creating high-quality MCP (Model Context Protocol) servers that enable LLMs to interact with external services through well-designed tools. Use when building MCP servers to integrate external APIs or services, whether in Python (FastMCP) or Node/TypeScript (MCP SDK).

0 1
Explore
nimeshgurung/artifact-hub-collections

canvas-design

Create beautiful visual art in .png and .pdf documents using design philosophy. You should use this skill when the user asks to create a poster, piece of art, design, or other static piece. Create original visual designs, never copying existing artists' work to avoid copyright violations.

0 1
Explore
nimeshgurung/artifact-hub-collections

brand-guidelines

Applies Anthropic's official brand colors and typography to any sort of artifact that may benefit from having Anthropic's look-and-feel. Use it when brand colors or style guidelines, visual formatting, or company design standards apply.

0 1
Explore
nimeshgurung/artifact-hub-collections

algorithmic-art

Creating algorithmic art using p5.js with seeded randomness and interactive parameter exploration. Use this when users request creating art using code, generative art, algorithmic art, flow fields, or particle systems. Create original algorithmic art rather than copying existing artists' work to avoid copyright violations.

0 1
Explore
nimeshgurung/artifact-hub-collections

template-skill

Replace with description of the skill and when Claude should use it.

0 1
Explore

Didn't find tool you were looking for?

Be as detailed as possible for better results