React\Promise\FunctionReduceTest::shouldAllowSparseArrayInputWithoutInitialValue PHP Method

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