PHPUnit throws a TypeError exception if called with a filename without extension

[morozov]

Q	A
PHPUnit version	8.4.1
PHP version	7.3.10
Installation Method	Composer

Summary

PHPUnit called with the name of a file that doesn't have an extension throws an unhandled TypeError exception.

How to reproduce

Assume there is a file without extension in the current directory (e.g. LICENSE).

$ phpunit LICENSE

Fatal error: Uncaught TypeError: substr() expects parameter 3 to be int, bool given in /home/morozov/Projects/dbal/vendor/phpunit/phpunit/src/TextUI/Command.php on line 808

TypeError: substr() expects parameter 3 to be int, bool given in /home/morozov/Projects/dbal/vendor/phpunit/phpunit/src/TextUI/Command.php on line 808

Call Stack:
    0.0002     491064   1. {main}() /home/morozov/Projects/dbal/vendor/phpunit/phpunit/phpunit:0
    0.0037    1047904   2. PHPUnit\TextUI\Command::main() /home/morozov/Projects/dbal/vendor/phpunit/phpunit/phpunit:61
    0.0037    1048016   3. PHPUnit\TextUI\Command->run() /home/morozov/Projects/dbal/vendor/phpunit/phpunit/src/TextUI/Command.php:159
    0.0037    1048016   4. PHPUnit\TextUI\Command->handleArguments() /home/morozov/Projects/dbal/vendor/phpunit/phpunit/src/TextUI/Command.php:167
    0.0047    1217712   5. substr() /home/morozov/Projects/dbal/vendor/phpunit/phpunit/src/TextUI/Command.php:808

Expected behavior

According to the usage, the first passed parameter is the test class. Since the class does not exist in the suite, PHPUnit should not run any tests and report a human-readable error.