Run tests on PHPUnit 9, on PHP 7.4 and add .gitattributes to exclude dev files from exports

[SimonFrings]

No description provided.

[clue]

@SimonFrings Thanks for the update!

It looks like this currently reports a warning, is this something you can look into?

https://travis-ci.org/github/graphp/graphviz/jobs/716530963#L526

It also looks like this creates a .phpunit.result.cache file when executed. Can we prevent or ignore this file?

[SimonFrings]

@SimonFrings Thanks for the update!

It looks like this currently reports a warning, is this something you can look into?

https://travis-ci.org/github/graphp/graphviz/jobs/716530963#L526

It also looks like this creates a .phpunit.result.cache file when executed. Can we prevent or ignore this file?

PHPUnit 9.3 released a new schema for the phpunit.xml configuration file. I had to migrate the file to the new format in order to avoid the warning. That also means every PHPUnit Version older than 9.3 will automatically report a warning when executing the test suite (because the new format is unknown).

It also appears that the <phpunit cacheResult="true|false"> XML configuration attribute was set to true instead of false as default. That caused the .phpunit.result.cache to be generated.

[clue]

@SimonFrings Thanks for the update! It looks like the new configuration file format is only supported by PHPUnit 9.3+, so older PHPUnit versions (on older PHP versions) will no longer generate a proper code coverage output.

This means we can not use a single configuration file that works across all PHPUnit versions referenced in this package. We can either ignore the warnings on some versions or ship multiple configuration files and configure our test jobs accordingly. Given PHPUnit's track record of deprecating and removing legacy functionality, there's a fair chance ignoring any warnings on newer versions isn't sustainable in the long run.

The result cache is kind of pointless for small libraries such as this one. I agree that turning it off is probably the best option for now. It's interesting old PHPUnit versions do not seem to complain about this (unknown) option. https://github.com/sebastianbergmann/phpunit/blob/8c908255db023c3861a8f3adc2cad1ed61dc4690/ChangeLog-9.3.md#934---2020-08-10 leads to sebastianbergmann/phpunit@a89b9ae, so it looks like this was supposed to be enabled as of PHPUnit 8+ but somewhat was disabled between PHPUnit 9 and PHPUnit 9.3.3.

[SimonFrings]

I went with the possibility to ship multiple configuration files. I told .travis.yml to use the phpunit.xml.dist for PHPUnit 9.3+ and the phpunit-legacy.xml.dist for older PHPUnit Versions.

[clue]

@SimonFrings Thanks for the update, changes LGTM!