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Fix flaky perf tests by replacing wall-clock thresholds with relative comparisons #195

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Merged
shellicar merged 1 commit into from
Apr 6, 2026
Merged

Fix flaky perf tests by replacing wall-clock thresholds with relative comparisons #195

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36 changes: 20 additions & 16 deletions apps/claude-cli/test/terminal-perf.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -30,19 +30,21 @@ describe('Terminal wrapping cache', () => {
const editor = createEditor();

// Prime: first render wraps all 10K lines and caches them
const primeStart = process.hrtime.bigint();
term.renderEditor(editor, '> ');
const primeMs = Number(process.hrtime.bigint() - primeStart) / 1_000_000;

// Append 1 line to displayBuffer
term.info('new line');

// Measure: second render wraps only the 1 new line
const start = process.hrtime.bigint();
const warmStart = process.hrtime.bigint();
term.renderEditor(editor, '> ');
const end = process.hrtime.bigint();
const warmMs = Number(process.hrtime.bigint() - warmStart) / 1_000_000;

const actual = Number(end - start) / 1_000_000;
const expected = process.env.CI ? 5 : 1;
expect(actual).toBeLessThan(expected);
// Cached render (1 new line) must be at least 10x faster than the cold render (10K lines).
// The ratio is typically 1000x+; 10x gives plenty of CI headroom without any absolute threshold.
expect(warmMs).toBeLessThan(primeMs / 10);
});

it('resize re-wrap at 10K history lines completes in under 2ms', () => {
Expand Down Expand Up @@ -77,13 +79,14 @@ describe('Terminal wrapping cache', () => {
// Simulate resize to 160 columns
screenColumns = 160;

const start = process.hrtime.bigint();
const resizeStart = process.hrtime.bigint();
term.renderEditor(editor, '> ');
const end = process.hrtime.bigint();
const resizeMs = Number(process.hrtime.bigint() - resizeStart) / 1_000_000;

const actual = Number(end - start) / 1_000_000;
const expected = process.env.CI ? 25 : 2;
expect(actual).toBeLessThan(expected);
// Sanity bound: re-wrapping 10K lines on any modern machine takes well under 50ms.
// No CI conditional — if this ever exceeds 50ms something is catastrophically wrong
// (e.g. accidentally O(n²)), and we want to know regardless of environment.
expect(resizeMs).toBeLessThan(50);
});

it('keystroke-only render at 10K history lines completes in under 1ms', () => {
Expand All @@ -97,16 +100,17 @@ describe('Terminal wrapping cache', () => {
const editor1 = createEditor();
const editor2 = insertChar(editor1, 'x');

// Prime: first render establishes cache baseline
// Prime: first render wraps all 10K lines and caches them
const primeStart = process.hrtime.bigint();
term.renderEditor(editor1, '> ');
const primeMs = Number(process.hrtime.bigint() - primeStart) / 1_000_000;

// Measure: keystroke-only render (editor changed, history unchanged)
const start = process.hrtime.bigint();
const warmStart = process.hrtime.bigint();
term.renderEditor(editor2, '> ');
const end = process.hrtime.bigint();
const warmMs = Number(process.hrtime.bigint() - warmStart) / 1_000_000;

const elapsedMs = Number(end - start) / 1_000_000;
const expected = process.env.CI ? 5 : 1;
expect(elapsedMs).toBeLessThan(expected);
// Cached render (history unchanged) must be at least 10x faster than the cold render (10K lines).
expect(warmMs).toBeLessThan(primeMs / 10);
});
});
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