Cover all expressions with integration tests

[norberttech]

Every expression is covered with a unit tests that looks like this:

<?php

    public function test_array_unpack() : void
    {
        $row = Row::create(
            Entry::int('id', 1),
            Entry::array('array_entry', [
                'status' => 'PENDING',
                'enabled' => true,
                'array' => ['foo' => 'bar'],
            ]),
        );

        $this->assertSame(
            [
                'status' => 'PENDING',
                'enabled' => true,
                'array' => ['foo' => 'bar'],
            ],
            (new ArrayUnpack(ref('array_entry')))->eval($row)
        );
    }

however this does not show how to use given expressions, integration tests would solve that problem, for example:

<?php

namespace Flow\ETL\Tests\Integration\Row\Reference\Expression;

use Flow\ETL\DSL\Entry;
use Flow\ETL\DSL\From;
use Flow\ETL\DSL\To;
use Flow\ETL\Flow;
use Flow\ETL\Memory\ArrayMemory;
use Flow\ETL\Row;
use Flow\ETL\Rows;
use PHPUnit\Framework\TestCase;
use function Flow\ETL\DSL\array_expand;
use function Flow\ETL\DSL\ref;

final class ArrayUnpackTest extends TestCase
{
    public function test_array_unpack() : void
    {
        (new Flow())
            ->read(
                From::rows(new Rows(
                    Row::with(Entry::int('id', 1), Entry::array('array', ['a' => 1, 'b' => 2, 'c' => 3])),
                ))
            )
            ->withEntry('expanded', array_expand(ref('array')))
            ->write(To::memory($memory = new ArrayMemory()))
            ->run();

        $this->assertSame(
            [
                ['id' => 1, 'array' => ['a' => 1, 'b' => 2, 'c' => 3], 'expanded' => 1],
                ['id' => 1, 'array' => ['a' => 1, 'b' => 2, 'c' => 3], 'expanded' => 2],
                ['id' => 1, 'array' => ['a' => 1, 'b' => 2, 'c' => 3], 'expanded' => 3],
            ],
            $memory->data
        );
    }
}

[stloyd]

@norberttech I think we have covered maybe not all of the tests as integration ones but for sure the critical ones are covered. I guess this task is done.