There are rare occasions when writing unit tests where I need to verify the value of a private property on a Typescript object instance.

Imagine SomeObject has a private property called PrivateProp. We can skip the type checking using any type assertion.

it('equals some value', () => {
  const someObject = new SomeObject();
  expect((<any>someObject).privateProp).to.eq 'some value';
});

This could also be expresses as (someObject as any)

See also This SO answer.