phpstream\tests\unit\operations\FlatMapOperationTest::testFlatMap PHP Method

    public function testFlatMap()
    {
        $instance = new FlatMapOperation([1, 2, 3], function () {
            return [4, 5, 6];
        });
        $result = $instance->toArray();
        $this->assertEquals([4, 5, 6, 4, 5, 6, 4, 5, 6], $result);
    }