diff --git a/circle.yml b/circle.yml
index 550389cab..7a5a15850 100644
--- a/circle.yml
+++ b/circle.yml
@@ -1,7 +1,29 @@
 machine:
   php:
     version: 5.6.17
+dependencies:
+  pre:
+    - curl -s -L -O https://github.com/phpbrew/phpbrew/raw/master/phpbrew
+    - chmod +x phpbrew
+    - sudo mv phpbrew /usr/bin/phpbrew
+    - phpbrew init
+    - phpbrew known --update
+    - phpbrew update
+    - phpbrew install 5.5.38
+    - phpbrew install 7.0.14
+    - phpbrew install 7.1.0
 
 test:
   override:
     - vendor/bin/phpunit tests --coverage-text
+    - composer update && vendor/bin/phpunit tests
+    - composer update --prefer-lowest && vendor/bin/phpunit tests
+
+    - source ~/.phpbrew/bashrc && phpbrew switch 5.5.38 && php -v && composer update && vendor/bin/phpunit tests
+    - source ~/.phpbrew/bashrc && phpbrew switch 5.5.38 && php -v && composer update --prefer-lowest && vendor/bin/phpunit tests
+
+    - source ~/.phpbrew/bashrc && phpbrew switch 7.0.14 && php -v && composer update && vendor/bin/phpunit tests
+    - source ~/.phpbrew/bashrc && phpbrew switch 7.0.14 && php -v && composer update --prefer-lowest && vendor/bin/phpunit tests
+
+    - source ~/.phpbrew/bashrc && phpbrew switch 7.1.0 && php -v && composer update && vendor/bin/phpunit tests
+    - source ~/.phpbrew/bashrc && phpbrew switch 7.1.0 && php -v && composer update --prefer-lowest && vendor/bin/phpunit tests
\ No newline at end of file
diff --git a/composer.json b/composer.json
index aed5ad7bf..357083cc5 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,7 @@
     "require-dev": {
         "guzzlehttp/guzzle": "6.2.1",
         "kevinrob/guzzle-cache-middleware": "1.4.1",
-        "phpunit/phpunit": "4.8.26",
+        "phpunit/phpunit": ">=4.8.26 <5.4",
         "phpdocumentor/phpdocumentor": "2.*",
         "predis/predis": "1.0.*",
         "zendframework/zend-serializer": "2.7.*"