mockPerformance()

mockPerformance(overrides): MockPerformanceResult

Creates a mock performance object on globalThis for Node.js tests.

remarque

Always call restore() for cleanup. Auto-restored after each test if forgotten.

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Parameters

overrides: Partial<Performance> = {}

Properties to override on the mock performance.

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Returns: MockPerformanceResult

Object containing the mock performance and restore function.

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Since

2.0.0

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Example

const { performance, restore } = mockPerformance({
  now: vi.fn(() => 12345),
});
expect(performance.now()).toBe(12345);
restore();

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Use Cases

Control timing 📌

Mock performance.now() to return deterministic timestamps. Critical for testing animations, timeouts, or performance markers.

#control#timing#performance#deterministic#timestamps#testing

const { restore } = mockPerformance({
  now: () => 1000
});
const time = performance.now(); // Always 1000
restore();

Test duration calculations

Verify elapsed time logic with predictable values.

#test#duration#elapsed#time#calculations#predictable

let time = 0;
const { restore } = mockPerformance({
  now: () => time
});

const start = performance.now();
time = 500;
const elapsed = performance.now() - start;

expect(elapsed).toBe(500);
restore();

MockPerformanceResult

Interface

Result of mockPerformance().

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Since

2.0.0

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Properties

performance: Performance

restore(): () => void

Returns

void