diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index f52821a..f695bac 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -9,11 +9,29 @@ variables:
 before_script:
   - docker login -u "gitlab-ci-token" -p "$CI_BUILD_TOKEN" registry.gitlab.com
 
+.test_build: &test_build
+  stage: test
+  script:
+    # Hack to set an array in /bin/sh
+    # http://unix.stackexchange.com/a/137571
+    - set $CI_BUILD_NAME
+    - export JOB=$(printf '%s\n' "$1")
+    - docker build -f "Dockerfile.$JOB" .
+  except:
+    - master
+
 .build_and_deploy: &build_and_deploy
   stage: build
   script:
     - docker build -t "$CI_REGISTRY_IMAGE:$CI_BUILD_NAME" -f "Dockerfile.$CI_BUILD_NAME" .
     - docker push "$CI_REGISTRY_IMAGE:$CI_BUILD_NAME"
+  only:
+    - master
+
+ruby-2.1 test: *test_build
+ruby-2.2 test: *test_build
+ruby-2.3 test: *test_build
+www-gitlab-com test: *test_build
 
 ruby-2.1: *build_and_deploy
 ruby-2.2: *build_and_deploy