Travis CI: Use the latest PHPUnit 6.x branch

[netweb]

Follow up to #39822 / [40536] where PHPunit 6.x support was added to use PHPUnit 6.1 for Travis CI PHP 7.x versions

PHPUnit 6.2 was released 2nd June 2017, and the latest 6.2.3 released 3rd July 2017

We should use the latest 6.x branches rather than the 6.1.x branch

Here's a Travis CI job testing this patch as at current SVN revision [41179]

​https://travis-ci.org/ntwb/wordpress/builds/258400758 via ​https://github.com/ntwb/wordpress/pull/4

[ayeshrajans]

I'm sorry if I'm missing something. Can't we composer global require phpunit/phpunit:^6.2?
Composer lately started to recommend the caret operator, and it should pick the latest available release. The patch #1 with asterisk should be functionally the same, but caret is a lot more commonly used in the documentation.

Ref: ​https://getcomposer.org/doc/articles/versions.md#caret-version-range-

[ayeshrajans]

A slightly different patch with the caret.

[ayeshrajans]

Please ignore my previous file. This one is newer and fixes the echo calls as well.

[netweb]

Thanks @ayeshrajans, hadn't seen this until you mentioned it, cheers +1

Refreshed patch uses ^6 and ^4 to use latest PHPUnit 6.x and 4.x respectively where required

​https://semver.mwl.be/#?package=phpunit%2Fphpunit&version=%5E6&minimum-stability=stable
​https://semver.mwl.be/#?package=phpunit%2Fphpunit&version=%5E4&minimum-stability=stable

[johnbillion]

I'm confident in PHPUnit's ability to follow semver without breaking compatibility within a major version, so let's do this.

[johnbillion]

In 41294:

Build/Test tools: Use the latest in the 4.x and 6.x branches of PHPUnit when running tests on Travis.

Props netweb, ayeshrajans

Fixes #41472

[johnbillion]

This should be back-ported to branches. Doesn't need a patch, I'll merge.

[johnbillion]

In 41295:

Build/Test tools: Use the latest in the 4.x and 6.x branches of PHPUnit when running tests on Travis for the 4.8 branch.

See #41472

Merges [41294] to the 4.8 branch.

[johnbillion]

In 41296:

Build/Test tools: Use the latest in the 4.x and 6.x branches of PHPUnit when running tests on Travis for the 4.7 branch.

See #41472

Merges [41294] to the 4.7 branch.

[johnbillion]

In 41297:

Build/Test tools: Use the latest in the 4.x and 5.x branches of PHPUnit when running tests on Travis for the 4.6 branch.

See #41472

[johnbillion]

In 41298:

Build/Test tools: Use the latest in the 4.x and 5.x branches of PHPUnit when running tests on Travis for the 4.5 branch.

See #41472

[johnbillion]

In 41299:

Build/Test tools: Use the latest in the 4.x and 5.x branches of PHPUnit when running tests on Travis for the 4.4 branch.

See #41472

[johnbillion]

In 41300:

Build/Test tools: Use the latest in the 4.x and 5.x branches of PHPUnit when running tests on Travis for the 4.3 branch.

See #41472

[johnbillion]

In 41301:

Build/Test tools: Use the latest in the 4.x and 5.x branches of PHPUnit when running tests on Travis for the 4.2 branch.

See #41472

[johnbillion]

In 41302:

Build/Test tools: Use the latest in the 4.x and 5.x branches of PHPUnit when running tests on Travis for the 4.1 branch.

See #41472

[johnbillion]

In 41303:

Build/Test tools: Use the latest in the 4.x and 5.x branches of PHPUnit when running tests on Travis for the 4.0 branch.

See #41472