diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..bc0863c
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "cif-tests"]
+	path = cif-tests
+	url = https://github.com/comes-group/cif-tests
diff --git a/cif-tests b/cif-tests
new file mode 160000
index 0000000..b75d28c
--- /dev/null
+++ b/cif-tests
@@ -0,0 +1 @@
+Subproject commit b75d28c082b4355be605e111690dca0ebf15bcca
diff --git a/test_runner.sh b/test_runner.sh
index 5923f5c..daa4fe1 100755
--- a/test_runner.sh
+++ b/test_runner.sh
@@ -1,8 +1,29 @@
 #!/usr/bin/sh
 
-for image in ../cif-tests/valid/*.cif; do
+exit_code=0
+
+echo "--- Valid tests: ---"
+for image in cif-tests/valid/*.cif; do
     echo "Running test on $image"
-    ./zardzewialy-dekoder-cif $image aaa.png
-    echo ""
+    stderr="$(./zardzewialy-dekoder-cif $image aaa.png 2>&1 > /dev/null)"
+    if [[ ${#stderr} != 0 ]]; then
+        echo "Failed on a valid test:"
+        echo $stderr
+        exit_code=1
+    fi
 done
 
+echo ""
+echo "--- Invalid tests: ---"
+for image in cif-tests/invalid/*.cif; do
+    echo "Running test on $image"
+    stderr="$(./zardzewialy-dekoder-cif $image aaa.png 2>&1 /dev/null)"
+    if [[ ${#stderr} == 0 ]]; then
+        echo "Error: preduced an invalid image"
+        exit_code=1
+    fi
+done
+
+rm aaa.png
+exit $exit_code
+