Update phpunit/phpunit requirement from ^8 to ^9

[dependabot[bot]]

Updates the requirements on phpunit/phpunit to permit the latest version.

Changelog

Sourced from phpunit/phpunit's changelog.

9.4.3 - 2020-11-10

Fixed

• #4446: The --no-logging and --no-coverage do not only affect XML configuration settings
• #4499: Restore support for case-insensitive namespaced class names when invoking the test runner with the test case file name
• #4514: --fail-on-skipped does not work

9.4.2 - 2020-10-19

Added

• Added missing PHPUnit\Framework\assertObjectEquals() and PHPUnit\Framework\objectEquals() wrapper functions

Changed

• PHPUnit\Framework\Assert::assertObjectEquals() is now static

9.4.1 - 2020-10-11

Fixed

• #4480: Methods with "static" return type (introduced in PHP 8) are not handled correctly by test double code generator

9.4.0 - 2020-10-02

Added

• #4462: Support for Cobertura XML report format
• #4464: Filter based on covered (@covers) / used (@uses) units of code
• #4467: Convenient custom comparison of objects

Changed

• The PHPUnit XML configuration generator (that is invoked using the --generate-configuration CLI option) now asks for a cache directory (default: .phpunit.cache)

Commits

• 9fa359f Prepare release
• cc2a3f8 Merge branch '8.5' into 9.4
• f5c8a5d Prepare release
• 078dd79 Merge branch '8.5' into 9.4
• 74e64bf Prepare release
• d6f4c3e Update tools
• 150b727 Closes #4514
• ee7054a Merge branch '8.5' into 9.4
• 81f56dc Update tools
• fe16318 Merge branch '8.5' into 9.4
• Additional commits viewable in compare view

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