TestCase::assertSame (and related exact comparisons) must compare float exactly #4966
Description
| Q | A |
|---|---|
| PHPUnit version | 9.5.10 |
| PHP version | 7.4 |
| Installation Method | Composer |
Summary
Currently test case like:
$this->assertSame(8.20234376757473, 8.20234376757474);
pass even if the numbers are different. They are really stored differently, test case:
$this->assertSame(bin2hex(pack('e', 8.20234376757473)), bin2hex(pack('e', 8.20234376757474)));
fails correctly.
It seems phpunit converts float numbers using default php float to string conversion which depends on php.ini precision configuration, test case like:
ini_set('precision', '20');
$this->assertSame(8.20234376757473, 8.20234376757474);
fails as expected.
Also, the float diff output has currently limited precision.
To fix exact comparisons & diff output, I propose to convert float numbers to string using function like:
/**
* Cast float to string with lossless precision.
*/
final public static function castFloatToString(float $value): string
{
$precisionBackup = ini_get('precision');
ini_set('precision', '-1');
try {
return (string) $value;
} finally {
ini_set('precision', $precisionBackup);
}
}