Test agains neweset dependencies

Author: alexander-schranz

.travis.yml

@@ -1,21 +1,29 @@
 language: php
 
-php:
-  - 7.0
-  - 7.1
-  - 7.2
+
+env:
+  global:
+    - USE_COMPOSER_LOCK=false
 
 matrix:
   include:
+    - php: 7.0
+      env:
+          - USE_COMPOSER_LOCK=true
     - php: 7.1
-      env: STATIC_ANALYSIS=true
+          - COMPOSER_FLAGS="--prefer-lowest"
+    - php: 7.2
+    - php: 7.3
+      env:
+          - STATIC_ANALYSIS=true
 
 cache:
   directories:
     - $HOME/.composer/cache
 
 install:
-  - composer install --no-interaction
+  - if [[ $USE_COMPOSER_LOCK != "false" ]]; then rm composer.lock; fi
+  - composer install --no-interaction $COMPOSER_FLAGS
   # coding style
   - if [[ $STATIC_ANALYSIS != "" ]]; then composer create-project symplify/easy-coding-standard temp/ecs; fi