add tests

Author: asbiin

.travis.yml

@@ -4,6 +4,8 @@ language: php
 
 php:
   - 7.3
+  - 7.4
+  - 8.0
 
 install:
   - composer install --prefer-dist

phpunit.xml.dist

@@ -10,4 +10,7 @@
       <directory>test</directory>
     </testsuite>
   </testsuites>
+  <php>
+    <env name="XDEBUG_MODE" value="coverage"/>
+  </php>
 </phpunit>