Clean up test suite

Author: SimonFrings

.travis.yml

@@ -16,7 +16,6 @@ matrix:
     - php: 7.3
     - php: 7.4
     - php: hhvm-3.18
-      install: composer require phpunit/phpunit:^5 --dev --no-interaction # requires legacy phpunit
   allow_failures:
     - php: hhvm-3.18
 

phpunit.xml.dist

@@ -1,11 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
-<phpunit bootstrap="vendor/autoload.php"
-         colors="true"
-         convertErrorsToExceptions="true"
-         convertNoticesToExceptions="true"
-         convertWarningsToExceptions="true"
->
+<phpunit bootstrap="vendor/autoload.php" colors="true">
     <testsuites>
         <testsuite name="Promise Timer Test Suite">
             <directory>./tests/</directory>