Manually download phpunit 5.7 on travis

.travis.yml

@@ -43,6 +43,10 @@ cache:
 before_install:
   - php --info
 
+  # Download phpunit 5.7
+  - wget https://phar.phpunit.de/phpunit-5.7.phar -O phpunit
+  - chmod u+x phpunit
+
   # Set up DB
   - if [[ "$DB" == 'pgsql' ]]; then createuser -U travis -s oc_autotest; fi
   - if [[ "$DB" == 'mysql' ]]; then mysql -u root -e 'create database oc_autotest;'; fi
@@ -96,7 +100,7 @@ script:
 
   # Run PHP tests
   - cd tests
-  - phpunit --configuration phpunit.xml
+  - ../phpunit --configuration phpunit.xml
   - if [[ "$PHP_COVERAGE" = "TRUE" ]]; then wget https://scrutinizer-ci.com/ocular.phar;
     fi
   - if [[ "$PHP_COVERAGE" = "TRUE" ]]; then php ocular.phar code-coverage:upload --format=php-clover