Expected size is wrong in assertCount error message

[JeroenDeDauw]

Q	A
PHPUnit version	7.3.5
PHP version	7.2.6
Installation Method	Composer

I have this and the test passes:

$this->assertCount( 6, $someGenerator );

I changed it from 6 to 5 to verify the test is being run

$this->assertCount( 5, $someGenerator );

Got error

Failed asserting that actual size 0 matches expected size 5.

While I expected to get

Failed asserting that actual size 6 matches expected size 5.

[sebastianbergmann]

I cannot reproduce this:

<?php declare(strict_types=1);
class Test extends PHPUnit\Framework\TestCase
{
    public function testOne(): void
    {
        $a = [1, 2, 3];
        
        $this->assertCount(4, $a);
    }
}

$ phpunit Test
PHPUnit 7.3.5 by Sebastian Bergmann and contributors.

F                                                                   1 / 1 (100%)

Time: 30 ms, Memory: 4.00MB

There was 1 failure:

1) Test::testOne
Failed asserting that actual size 3 matches expected size 4.

/home/sb/Test.php:8

FAILURES!
Tests: 1, Assertions: 1, Failures: 1.

[JeroenDeDauw]

My input is a Generator, not an array. I just realized that Generator is not countable, so the "0" in the failure message makes some form of sense. Still, either assertCount should work fully with Generator or not at all.

[sebastianbergmann]

Thank you for your report.

Please provide a minimal, self-contained, reproducing test case that shows the problem you are reporting.

Without such a minimal, self-contained, reproducing test case I will not be able to investigate this issue.

[kubawerlos]

    public function testGenerator()
    {
        $generator = static function () {
            yield 1;
            yield 2;
            yield 3;
        };

        static::assertCount(3, $generator());
        static::assertCount(4, $generator());
    }

[sebastianbergmann]

• Generator does not implement Countable
• Generator implements Iterator
• Since 4123b6a (to fix PHPUnit and Generators  #2149), PHPUnit iterates over the elements yielded by the generator to count them
• Due to this iteration, the second assertCount() in the example above fails because the generator yielded all of its elements already

[sebastianbergmann]

AFAICS, the only sensible thing to do here would be to disallow assertCount() on generators.

[JeroenDeDauw]

The issue does not depend on calling assertCount twice.

   static::assertCount(4, $generator());

That assert alone does the trick. You will get the error saying 0 does not match 4.

[JeroenDeDauw]

Disallowing Generator instances would be one way to make the behavior of assertCount consistent, but has the downsides that

• it is a breaking change
• assertCount not being able to work with any iterable is unintuitive

[guilliamxavier]

Sorry for bringing more issue rather than a solution, but besides generators, there is the same problem with other non-countable, forward-only (non-rewindable) iterators/traversables, e.g.:

assertCount(4, new \NoRewindIterator(new \ArrayIterator([1, 2, 3])));

or things like PDOStatement (even though a bit far-fetched)...

[JeroenDeDauw]

The fix that is up should also take care of those, see #3304

[stale]

This issue has been automatically marked as stale because it has not had activity within the last 60 days. It will be closed after 7 days if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically closed because it has not had activity since it was marked as stale. Thank you for your contributions.

[epdenouden]

!stale