MockTracker.property method | Node.js node:test module | Bun

Creates a mock for a property value on an object. This allows you to track and control access to a specific property, including how many times it is read (getter) or written (setter), and to restore the original value after mocking.

test('mocks a property value', (t) => {
const obj = { foo: 42 };
const prop = t.mock.property(obj, 'foo', 100);

assert.strictEqual(obj.foo, 100);
assert.strictEqual(prop.mock.accessCount(), 1);
assert.strictEqual(prop.mock.accesses[0].type, 'get');
assert.strictEqual(prop.mock.accesses[0].value, 100);

obj.foo = 200;
assert.strictEqual(prop.mock.accessCount(), 2);
assert.strictEqual(prop.mock.accesses[1].type, 'set');
assert.strictEqual(prop.mock.accesses[1].value, 200);

prop.mock.restore();
assert.strictEqual(obj.foo, 42);
});

The object whose value is being mocked.

An optional value used as the mock value for object[propertyName]. Default: The original property value.

A proxy to the mocked object. The mocked object contains a special mock property, which is an instance of [MockPropertyContext][], and can be used for inspecting and changing the behavior of the mocked property.