Break stub/restore test-helpers into their own stub.sh file

test/stub.sh

@@ -0,0 +1,35 @@
+# Stub commands for testing purposes.
+#
+# Arguments:
+#   - $1: Name of command to stub.
+#   - $2: Output will go to STDERR when $2 is "STDERR".
+#
+stub() {
+  local cmd="$1"
+  if [ "$2" == "STDERR" ]; then local redirect=" 1>&2"; fi
+
+  if [[ "$(type "$cmd" | head -1)" == *"is a function" ]]; then
+    local source="$(type "$cmd" | tail -n +2)"
+    source="${source/$cmd/non_stubbed_${cmd}}"
+    eval "$source"
+  fi
+  eval "$(echo -e "${1}() {\n  echo \"$1 stub: \$@\"$redirect\n}")"
+}
+
+# Restore the original command/function that was stubbed with stub().
+#
+# Arguments:
+#   - $1: Name of command to restore.
+#
+restore() {
+  local cmd="$1"
+  unset -f "$cmd"
+  if type "non_stubbed_${cmd}" &>/dev/null; then
+    if [[ "$(type "non_stubbed_${cmd}" | head -1)" == *"is a function" ]]; then
+      local source="$(type "non_stubbed_$cmd" | tail -n +2)"
+      source="${source/non_stubbed_${cmd}/$cmd}"
+      eval "$source"
+      unset -f "non_stubbed_${cmd}"
+    fi
+  fi
+}