Add test for Dockerfiles

test.mk

@@ -2,10 +2,11 @@
 yml_files:=$(shell find . -name "*.yml")
 json_files:=$(shell find . -name "*.json")
 jinja_files:=$(shell find . -name "*.j2")
+images = $(shell git diff --name-only $(TRAVIS_COMMIT_RANGE) | python util/parsefiles.py)
 
 test: test.syntax test.edx_east_roles
 
-test.syntax: test.syntax.yml test.syntax.json test.syntax.jinja
+test.syntax: test.syntax.yml test.syntax.json test.syntax.jinja test.syntax.dockerfiles
 
 test.syntax.yml: $(patsubst %,test.syntax.yml/%,$(yml_files))
 
@@ -22,5 +23,8 @@ test.syntax.jinja: $(patsubst %,test.syntax.jinja/%,$(jinja_files))
 test.syntax.jinja/%:
 	cd playbooks && python ../tests/jinja_check.py ../$*
 
+test.syntax.dockerfiles:
+	python util/check_dockerfile_coverage.py "$(images)"
+	
 test.edx_east_roles:
 	tests/test_edx_east_roles.sh