StringMatchesFormatDescription Does Not Handle Escaped % Properly

[mkasberg]

Q	A
PHPUnit version	6.5.3
PHP version	7.0.22-0ubuntu0.17.04.1
Installation Method	Git

I would expect the following test case to pass because the format string '%%' should produce a literal '%' (sprintf). But it fails in PHPUnit 6.5.3.

StringMatchesFormatDescriptionTest.php

<?php

use PHPUnit\Framework\TestCase;

class StringMatchesFormatDescriptionTest extends TestCase {

    public function testEscapedPercent() {
        $this->assertStringMatchesFormat('This %%d is escaped.', 'This %d is escaped.');
    }

}

Sample Output:

$ ./phpunit StringMatchesFormatDescriptionTest.php 
PHPUnit 6.5.3 by Sebastian Bergmann and contributors.

Runtime:       PHP 7.0.22-0ubuntu0.17.04.1 with Xdebug 2.5.0
Configuration: /home/mkasberg/repositories/phpunit/phpunit.xml

F                                                                   1 / 1 (100%)

Time: 436 ms, Memory: 4.00MB

There was 1 failure:

1) StringMatchesFormatDescriptionTest::testEscapedPercent
Failed asserting that string matches format description.
--- Expected
+++ Actual
@@ @@
-This %%d is escaped.
+This %d is escaped.

/home/mkasberg/repositories/phpunit/src/Framework/Constraint/Constraint.php:117
/home/mkasberg/repositories/phpunit/src/Framework/Constraint/Constraint.php:62
/home/mkasberg/repositories/phpunit/src/Framework/Assert.php:2116
/home/mkasberg/repositories/phpunit/src/Framework/Assert.php:1768
/home/mkasberg/repositories/phpunit/StringMatchesFormatDescriptionTest.php:8
/home/mkasberg/repositories/phpunit/src/Framework/TestCase.php:1071
/home/mkasberg/repositories/phpunit/src/Framework/TestCase.php:939
/home/mkasberg/repositories/phpunit/src/Framework/TestResult.php:698
/home/mkasberg/repositories/phpunit/src/Framework/TestCase.php:894
/home/mkasberg/repositories/phpunit/src/Framework/TestSuite.php:755
/home/mkasberg/repositories/phpunit/src/TextUI/TestRunner.php:546
/home/mkasberg/repositories/phpunit/src/TextUI/Command.php:195
/home/mkasberg/repositories/phpunit/src/TextUI/Command.php:148

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

---

I skimmed the source code for StringMatchesFormatDescription.php, and it is perhaps worth noting that we also seem to be missing a few other descriptors which are supported by PHP. For example, %b, %E, and %g. (Should we expect PHPUnit to support all of these?)

None of these are major bugs since it's certainly possible to work around them, but it might be nice to have better support for format string matching.

[sebastianbergmann]

I would consider (separate) pull requests that fix % escaping and add missing formatting placeholders.

[mkasberg]

I think I could take a stab at this. I'll see what I can come up with...