spyOn isDevMode() in Angular 6+ Unit Tests?

My code includes an if block like this

Service:

import { isDevMode } from '@angular/core';

export class MyService {
constructor() {}

methodToTest(): {
if (!isDevMode()) {
doSomething();
} else {
doSomethingDifferentInDevMode();
}
}
}


my-service.spec.ts (the relevant lines only):

it('should run doSomething() when isDevMode() returns false', () => {
// what should i do here to mock a false value return for isDevMode() ?
expect(doSomething).toHaveBeenCalled();
});


How do i spyOn the isDevMode() to make it return false for this single Angular unit test so that i may test that doSomething() is called?

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