How to test a function that output is random using Jest?

I used:

beforeEach(() => {
    jest.spyOn(global.Math, 'random').mockReturnValue(0.123456789);
});

afterEach(() => {
    jest.spyOn(global.Math, 'random').mockRestore();
})

It is easy to add and restores the functionality outside the tests.

Here's what I put at the top of my test file:

const mockMath = Object.create(global.Math);
mockMath.random = () => 0.5;
global.Math = mockMath;

In tests run from that file, Math.random always returns 0.5.

Full credit should go to this for the idea: https://stackoverflow.com/a/40460395/2140998, which clarifies that this overwrite is test-specific. My Object.create is just my additional extra little bit of caution avoiding tampering with the internals of Math itself.