Not a case with regular Packagist packages, but some custom installers with custom repos do this, and the current behavior should not randomly change at some point, as that would cause downstream breakage.
The `LibraryInstallerTest::testUninstall()` method mocks a `Package` object, but did not set an expectation for a call to `getName()`, while that method _is_ called in the `LibraryInstaller::uninstall()` method.
Without expectation, the mock returns `null`, which was subsequently being passed on to `strpos()` leading to the below error.
Fixes:
```
Deprecation triggered by Composer\Test\Installer\LibraryInstallerTest::testUninstall:
strpos(): Passing null to parameter #1 ($haystack) of type string is deprecated
Stack trace:
0 [internal function]: Symfony\Bridge\PhpUnit\DeprecationErrorHandler->handleError(8192, '...', '...', 202)
1 src/Composer/Installer/LibraryInstaller.php(202): strpos(NULL, '...')
2 vendor/react/promise/src/FulfilledPromise.php(28): Composer\Installer\LibraryInstaller->Composer\Installer\{closure}(NULL)
3 src/Composer/Installer/LibraryInstaller.php(208): React\Promise\FulfilledPromise->then(Object(Closure))
4 tests/Composer/Test/Installer/LibraryInstallerTest.php(221): Composer\Installer\LibraryInstaller->uninstall(Object(Mock_InstalledRepositoryInterface_e3699f95), Object(Mock_Package_e4571076))
...
```
Not all tests in the `InstallerTest` class actually create a temporary directory and set the `$this->tempComposerHome` property.
Those tests which didn't, throw a notice in PHP 8.1.
Fixes 3 notices along the lines of:
```
Deprecation triggered by Composer\Test\InstallerTest::tearDown:
is_dir(): Passing null to parameter #1 ($filename) of type string is deprecated
Stack trace:
0 [internal function]: Symfony\Bridge\PhpUnit\DeprecationErrorHandler->handleError(8192, '...', '...', 53)
1 tests/Composer/Test/InstallerTest.php(53): is_dir(NULL)
...
```
... to proof the existence of the bug and demonstrate the effect.
Note: in the test the backtrack limit is being lowered (and restored back to the default afterwards) to prevent the tests needing ridiculously huge test fixture files.
megubyte