add env to make ctest print on failure
diff --git a/.travis.yml b/.travis.yml
index 83c52f0..021b8b5 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -13,6 +13,9 @@
     - os: osx
       env: BUILD_TYPE=Release STD=c++11
 
+env:
+    - CTEST_OUTPUT_ON_FAILURE=1
+
 language:
     - cpp