jasmine.getEnv().allowRespy(true);
OR
beforeEach(() => { spyOn(some, "method").and.returnValue(X) })
it("Test", () => { some.method = jasmine.createSpy().and.returnValue(Y) })
jasmine.getEnv().allowRespy(true);
OR
beforeEach(() => { spyOn(some, "method").and.returnValue(X) })
it("Test", () => { some.method = jasmine.createSpy().and.returnValue(Y) })