Refactor “tests/default.nix” file

tests/default.nix

@@ -5,59 +5,90 @@
 let
   packs = (import ../.).packs;
 
+  # “e” stands for “executable”.
+  # Attribute name is executable name.
+  # Attribute value is an escaped full path in Nix store to an executable.
+  # For instance { dc = "'/nix/store/…-bc-…/bin/dc'"; }
+  e = builtins.mapAttrs (n: v: pkgs.lib.escapeShellArg "${v}/bin/${n}") {
+    cat = pkgs.coreutils;
+    cp = pkgs.coreutils;
+    id = pkgs.coreutils;
+    ln = pkgs.coreutils;
+    sleep = pkgs.coreutils;
+    timeout = pkgs.coreutils;
+
+    dc = pkgs.bc;
+    grep = pkgs.gnugrep;
+    tar = pkgs.gnutar;
+    xargs = pkgs.findutils;
+
+    pgrep = pkgs.procps;
+    ps = pkgs.procps;
+  };
+
+  guardDependencies =
+    builtins.concatStringsSep "\n" (map (executable: ''
+      if ! [[ -r ${executable} ]] || ! [[ -e ${executable} ]]; then
+        >&2 printf 'Executable "%s" is not found!\n' ${executable}
+        exit 1
+      fi
+    '') (builtins.attrValues e));
+
   smokeTest = pack: pkgs.runCommandLocal "smoketest" {
     server = pack.server;
     world = ./testdata/SmokeTest.tar.gz;
     props = ./testdata/server.properties;
-    buildInputs = with pkgs; [ jre8 rsync procps psmisc tmux ];
+    buildInputs = with pkgs; [ jre8 rsync tmux ];
 
     # Enable web access
     __noChroot = 1;
   } ''
-    set -e
+    set -Eeuo pipefail || exit
 
-    ln -s $server server
-    tar xvzf $world
-    cat $props > server.properties
+    # Guard dependencies first
+    ${guardDependencies}
+
+    ${e.ln} -s -- "$server" server
+    ${e.tar} -xvz --file="$world"
+    ${e.cat} -- "$props" > server.properties
     echo -n server-port= >> server.properties
-    id -u | ${pkgs.bc}/bin/dc -e '? 1000 % 30000 + p' >> server.properties
-    cat server.properties
+    ${e.id} -u | ${e.dc} -e '? 1000 % 30000 + p' >> server.properties
+    ${e.cat} server.properties
 
     echo 'eula=true' > eula.txt
 
     export SKIP_TMUX=1
     export KILL_PROMETHEUS=1
 
-    echo | timeout -s 9 900 bash server/start.sh -Dfml.queryResult=confirm &
-    sleep 3
+    echo | ${e.timeout} -s 9 900 bash server/start.sh -Dfml.queryResult=confirm &
+    ${e.sleep} 3
 
     terminate() {
+      set -Eeuo pipefail || exit
       echo 'Exiting.'
-      set +e
-      pgrep -s 0 | grep -v "^$$$" | xargs kill
-      set -e
+      ${e.pgrep} -s 0 | (${e.grep} -v "^$$$" || true) | ${e.xargs} kill
       echo 'Exited.'
     }
 
     time=0
     while true; do
-      grep 'Task Failed Successfully' logs/latest.log && {
+      if ${e.grep} 'Task Failed Successfully' logs/latest.log; then
         echo 'Smoke test successful. Exiting.'
         terminate
-        cp logs/latest.log $out
+        ${e.cp} logs/latest.log -- "$out"
         exit 0
-      }
-      ps -u $UID | grep -q java || {
-        echo 'Java process unexpectedly terminated'
-	exit 1
-      }
-      time=$(($time + 1))
-      if [[ $time -gt 1000 ]]; then
-        echo 'Exiting with timeout'
-        terminate
+      fi
+      if ! ${e.ps} -u "$UID" | ${e.grep} -q java; then
+        >&2 echo 'Java process unexpectedly terminated'
+        exit 1
+      fi
+      time=$(( time + 1 ))
+      if (( time > 1000 )); then
+        >&2 echo 'Exiting with timeout'
+        >&2 terminate
         exit 1
       fi
-      sleep 1
+      ${e.sleep} 1
     done
   '';
 in