React\Promise\FunctionReduceTest::shouldReducePromisedValuesWithoutInitialValue PHP Method

    public function shouldReducePromisedValuesWithoutInitialValue()
    {
        $mock = $this->createCallableMock();
        $mock->expects($this->once())->method('__invoke')->with($this->identicalTo(6));
        reduce([resolve(1), resolve(2), resolve(3)], $this->plus())->then($mock);
    }