SQSCANGHA-89 Fix possible command injection

It is unlikely to be a real concern, since an attacker having the possibility to edit a pipeline can easily execute any command, but at least our step won't be involved

test/assertFileContains

@@ -1,10 +1,14 @@
 #!/bin/bash
 
+set -eou pipefail
+
 error() { echo -e "\\e[31m✗ $*\\e[0m"; }
 
-assertFileExists $1
+scriptDir=$(dirname -- "$(readlink -f -- "${BASH_SOURCE[0]}")")
 
-if ! grep -q $2 $1; then
+$scriptDir/assertFileExists "$1"
+
+if ! grep -q "$2" "$1"; then
   error "'$2' not found in '$1'"
   exit 1
 fi