Plan for the future (see #3130): Allow for phpunit 5.x. #3139
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
I started to fix #3130, but then stopped when I realized that mixing Drush with Drupal prevents us from using phpunit 5.x, and erg sebastion/version 2.x, making the upgrade pointless.
However, I realized that at some point, Drupal will upgrade to phpunit 5.x. While we cannot anticipate every upgrade that Drupal might make, phpunit 4.x is very old, so this is probably overdue, or at least likely to happen eventually.
This PR sets up highest / lowest testing for the isolation tests, and allows the isolation tests to run across different versions of phpunit and sebastion/version. This will give us the flexibility to test with multiple versions of other libraries in the future, if we so desire.
The value for Drush being ahead of the game on upgrades is that it allows newer versions of Drupal to be used with more versions of Drush, making
composer update
easier to get through when there are minor Drupal upgrades. It behoves us to do this due to the limitations in Composer that can come into play when the dependency analysis of an upgrade is complicated (e.g. as it was for the upgrade to Drupal 8.4.0).