React\Promise\FunctionReduceTest::shouldReduceEmptyInputWithInitialPromise PHP Method

    public function shouldReduceEmptyInputWithInitialPromise()
    {
        $mock = $this->createCallableMock();
        $mock->expects($this->once())->method('__invoke')->with($this->identicalTo(1));
        reduce([], $this->plus(), resolve(1))->then($mock);
    }