vault-bin: add passthru.tests

pkgs/tools/security/vault/vault-bin.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, unzip }:
+{ stdenv, fetchurl, unzip, nixosTests }:
 
 let
   version = "1.5.5";
@@ -44,6 +44,8 @@ in stdenv.mkDerivation {
     echo "complete -C $out/bin/vault vault" > $out/share/bash-completion/completions/vault
   '';
 
+  passthru.tests.vault = nixosTests.vault;
+
   meta = with stdenv.lib; {
     homepage = "https://www.vaultproject.io";
     description = "A tool for managing secrets, this binary includes the UI";