ArraysTest::testFlatten PHP Method

    public function testFlatten()
    {
        // Arrange
        $a = [1, 2, [3, [4]]];
        $a2 = [1, 2, [3, [[4]]]];
        // Act
        $x = __::flatten($a);
        $x2 = __::flatten($a2, true);
        // Assert
        $this->assertEquals([1, 2, 3, 4], $x);
        $this->assertEquals([1, 2, 3, [[4]]], $x2);
    }