chore: debug phpunit issue

Author: atymic

.gitignore

@@ -1,4 +1,5 @@
 /vendor
 build
 composer.phar
-composer.lock
+composer.lock
+.phpunit.result.cache

.travis.yml

@@ -15,6 +15,8 @@ before_script:
     - travis_retry composer update ${COMPOSER_FLAGS} --no-interaction --prefer-source
 
 script:
+    - phpunit --version
+    - ./vendor/bin/phpunit --version
     - phpunit --coverage-text --coverage-clover=coverage.clover
 
 after_script: