Try again to fix travis failing at every sqlite tests

.travis.yml

@@ -10,17 +10,12 @@ php:
 services:
   - mysql
 
-cache:
-  directories:
-    - $HOME/.composer/cache
-    - $HOME/vendor
-
 before_install:
   - mysql -e 'CREATE DATABASE 2fauth_test;'
 
 before_script:
   - travis_retry composer self-update
-  - travis_retry composer install --no-interaction --prefer-source
+  - travis_retry composer install --no-interaction
   # no need to use a dedicated Travis .env file as phpunit
   # will use .env.testing by default
 

phpunit.xml

@@ -30,6 +30,8 @@
     </testsuites>
     <php>
         <env name="APP_ENV" value="testing"/>
-        <!-- Use .env.testing to customize other testing vars -->
+        <!-- following values override .env.testing vars -->
+        <env name="DB_CONNECTION" value="sqlite"/>
+        <env name="DB_DATABASE" value=":memory:"/>
     </php>
 </phpunit>