fix(tui): replace flaky setTimeout(0) tick() with robust flush utility in TUI tests

[JeremyDev87]

Problem

TUI integration tests intermittently fail in CI because tick() only waits one macrotask (setTimeout(resolve, 0)), but Ink (React) rendering sometimes needs 2-3 macrotask cycles to complete the event → state update → reconcile → render pipeline.

Example failure (PR #1117 CI, eventbus-ui.integration.spec.tsx:313):

expect(lastFrame()).toContain('RUNNING')
// Actual: full TUI frame rendered but still showing 'idle' instead of 'RUNNING'

Same test passes in PRs #1114 and #1115 — classic flaky timing issue.

Root Cause

// Current: single macrotask — not enough for Ink rendering pipeline
const tick = () => new Promise(resolve => setTimeout(resolve, 0));

This pattern is duplicated in 5 files with 74 await tick() call sites:

• eventbus-ui.integration.spec.tsx (44 calls)
• dashboard-app.spec.tsx (14 calls)
• transport-tui.integration.spec.tsx (7 calls)
• __perf__/memory-stability.spec.tsx (5 calls)
• __perf__/rendering-performance.spec.tsx (4 calls)

Solution

1. Create shared test utility: apps/mcp-server/src/tui/testing/tui-test-utils.ts

/**
 * Flush multiple macrotask cycles so Ink completes its render pipeline.
 * Replaces the fragile single-setTimeout tick() used across TUI tests.
 */
export async function flushInk(cycles = 3): Promise<void> {
  for (let i = 0; i < cycles; i++) {
    await new Promise(resolve => setTimeout(resolve, 0));
  }
}

/**
 * Retry an assertion until it passes or times out.
 * Use for frame content assertions that depend on Ink render timing.
 */
export async function waitForFrame(
  getFrame: () => string | undefined,
  assertion: (frame: string) => void,
  timeoutMs = 500,
): Promise<void> {
  const start = Date.now();
  let lastError: Error | undefined;
  while (Date.now() - start < timeoutMs) {
    try {
      assertion(getFrame() ?? '');
      return;
    } catch (err) {
      lastError = err as Error;
      await new Promise(resolve => setTimeout(resolve, 10));
    }
  }
  throw lastError ?? new Error('waitForFrame timeout');
}

2. Replace tick() in all 5 files

// BEFORE (each file):
const tick = () => new Promise(resolve => setTimeout(resolve, 0));

// AFTER (each file):
import { flushInk } from './testing/tui-test-utils';
// or: import { flushInk } from '../testing/tui-test-utils';

Then replace await tick() → await flushInk() across all 74 call sites.

3. (Optional) Migrate critical assertions to waitForFrame

For assertions most prone to flakiness (long tests with many sequential events), use waitForFrame:

// BEFORE:
await tick();
expect(lastFrame()).toContain('RUNNING');

// AFTER:
await waitForFrame(lastFrame, frame => expect(frame).toContain('RUNNING'));

Files to Modify

File	Changes
src/tui/testing/tui-test-utils.ts	CREATE — flushInk() + waitForFrame()
src/tui/testing/tui-test-utils.spec.ts	CREATE — unit tests for utilities
src/tui/eventbus-ui.integration.spec.tsx	Replace tick → flushInk (44 sites)
src/tui/dashboard-app.spec.tsx	Replace tick → flushInk (14 sites)
src/tui/transport-tui.integration.spec.tsx	Replace tick → flushInk (7 sites)
src/tui/__perf__/rendering-performance.spec.tsx	Replace tick → flushInk (4 sites)
src/tui/__perf__/memory-stability.spec.tsx	Replace tick → flushInk (5 sites)

Verification

# Run all TUI tests multiple times to confirm no flakiness
for i in {1..5}; do
  yarn workspace codingbuddy test -- --testPathPattern="src/tui/(eventbus|dashboard|transport|__perf__)" && echo "Run $i: PASS" || echo "Run $i: FAIL"
done

Acceptance Criteria

• Shared flushInk() utility created with tests
• No inline tick() definitions remain in TUI test files
• All 74 call sites migrated to flushInk()
• TUI tests pass 5 consecutive runs locally
• CI passes