Adding BC break test (#86)

* Adding BC break test

* make it automatically detect latest version

* Test adding a BC break

* make sure code works :/

* Try to add another BC break

* Adding a third BC break.

(revering others)

* Reverted all "test BC breaks"

* Moved around code

* minor

* minor

.travis.yml

@@ -23,9 +23,16 @@ matrix:
     allow_failures:
         - php: nightly
     include:
+        - php: 7.2
+          name: Backward compatibillity check
+          env: DEPENDENCIES="roave/backward-compatibility-check" TEST_COMMAND="./vendor/bin/roave-backward-compatibility-check"
         - php: 7.1
+          name: Lowest version of dependencies
           env: COMPOSER_FLAGS="--prefer-stable --prefer-lowest" COVERAGE=true TEST_COMMAND="composer test-ci"
 
+before_install:
+    - if ! [ -v "$DEPENDENCIES" ]; then composer require --no-update ${DEPENDENCIES}; fi;
+
 install:
     - composer update ${COMPOSER_FLAGS} --prefer-source --no-interaction