diff --git a/conf/app.src b/conf/app.src
index 0071b42..d6d776d 100644
--- a/conf/app.src
+++ b/conf/app.src
@@ -3,4 +3,4 @@ SOURCE_SUM=c21eefaa87fca836e17d874296e67baf181ab5594f705090247614faae219d01
 SOURCE_SUM_PRG=sha256sum
 SOURCE_FORMAT=tar.gz
 SOURCE_IN_SUBDIR=true
-SOURCE_FILENAME=
+SOURCE_FILENAME=mattermost-4.3.0-linux-amd64.tar.gz
diff --git a/test.sh b/test.sh
index 57b9e3c..bd52d6f 100755
--- a/test.sh
+++ b/test.sh
@@ -5,6 +5,7 @@
 set -e
 
 # Configuration constants
+APP_ID="mattermost"
 APP_DIR="/vagrant"
 
 function _usage() {
@@ -46,9 +47,42 @@ function _vagrant_ssh() {
   return $exit_code
 }
 
+# Pre-download the app source archive declared in an app.src file.
+# The local archive will be used during tests, instead of being re-downloaded every time.
+#
+# TODO: let package_check do the caching itself
+function _cache_app_source() {
+  local app_src="conf/app.src"
+  if [ ! -e "conf/app.src" ]; then
+    return
+  fi
+
+  local src_url=$(grep 'SOURCE_URL=' "$app_src" | cut -d= -f2-)
+  local src_format=$(grep 'SOURCE_FORMAT=' "$app_src" | cut -d= -f2-)
+  local src_filename=$(grep 'SOURCE_FILENAME=' "$app_src" | cut -d= -f2-)
+  if [ "$src_filename" = "" ] ; then
+    src_filename="app.${src_format}"
+  fi
+
+  local lxc_name="pchecker_lxc"
+  local lxc_root="/var/lib/lxcsnaps/${lxc_name}/snap0/rootfs"
+  local local_src_dir="${lxc_root}/opt/yunohost-apps-src/${APP_ID}"
+
+  local file_exists=false
+  _vagrant_ssh "sudo test -e ${local_src_dir}/${src_filename}" && file_exists=true
+
+  if [ "$file_exists" = false ]; then
+    echo "--- Downloading and caching app source ---"
+    _vagrant_ssh " \
+      sudo mkdir -p ${local_src_dir} && \
+      sudo wget -O ${local_src_dir}/${src_filename} ${src_url};";
+  fi
+}
+
 function setup() {
   echo "--- Setting up Vagrant VM ---"
   vagrant up --provision
+  _cache_app_source
 }
 
 function test_package_check() {