Add test with lowest composer flags (#40)

* Add test with lowest composer flags

* Do not use coverage

.travis.yml

@@ -1,22 +1,40 @@
 language: php
 
+cache:
+    directories:
+        - $HOME/.composer/cache/files
+
 php:
   - 5.4
   - 5.5
   - 5.6
   - 7.0
+  - 7.1
   - hhvm
 
-before_script:
-  - composer self-update
-  - composer install --no-interaction --prefer-source --dev
-  - ~/.nvm/nvm.sh install v0.6.14
-  - ~/.nvm/nvm.sh run v0.6.14
-
-script:
-  - make test
+env:
+  global:
+    - TEST_COMMAND="composer test"
 
 matrix:
   allow_failures:
     - php: hhvm
   fast_finish: true
+  include:
+    - php: 5.4
+      env: COMPOSER_FLAGS="--prefer-stable --prefer-lowest"
+
+before_install:
+  - if [[ $COVERAGE != true ]]; then phpenv config-rm xdebug.ini || true; fi
+
+install:
+  # To be removed when this issue will be resolved: https://github.com/composer/composer/issues/5355
+  - if [[ "$COMPOSER_FLAGS" == *"--prefer-lowest"* ]]; then travis_retry composer update --prefer-dist --no-interaction --prefer-stable --quiet; fi
+  - travis_retry composer update ${COMPOSER_FLAGS} --prefer-dist --no-interaction
+
+before_script:
+  - ~/.nvm/nvm.sh install v0.6.14
+  - ~/.nvm/nvm.sh run v0.6.14
+
+script:
+  - $TEST_COMMAND

composer.json

@@ -31,6 +31,10 @@
             "GuzzleHttp\\Tests\\Ring\\": "tests/"
         }
     },
+    "scripts": {
+        "test": "make test",
+        "test-ci": "make coverage"
+    },
     "extra": {
         "branch-alias": {
             "dev-master": "1.1-dev"