accomodate bsd-like macos with some tweaks to test script

focused more on functions and returns rather than exiting subprocesses

test/gui/run-gui-test

@@ -1,26 +1,48 @@
 #!/usr/bin/sh
+
 #   check if we can open xeyes and view it from denv
 #   only run this with docker machines right now
 
-set -o nounset
-set -o errexit
+docker_check() {
+  if ! command -v docker > /dev/null 2>&1; then
+    printf "docker not available. Not running test."
+    return 1
+  fi
+  return 0
+}
+
+build_test_image() {
+  cd "${1}" || return 1
+  docker build . -t "${2}"
+}
 
-if ! command -v docker > /dev/null 2>&1; then
-  printf "docker not available. Not running test."
-  exit 1
-fi
+run_gui_test() {
+  cd "${1}" || return 1
+  "${2}" init --clean-env "${3}:latest" || return 2
+  "${2}" xeyes || return 3
+  cd || return 4
+  rm -r "${1}"
+}
 
-_run_gui_test_dir="$(cd -- "$(dirname -- "$0")" && pwd)"
-_denv_dir="$(cd -- "${_run_gui_test_dir}/../../" && pwd)"
-_denv="${_denv_dir}/denv"
-_test_image_name="denv-gui-test-image"
+main() {
+  _run_gui_test_dir="$(cd -- "$(dirname -- "$0")" && pwd)"
+  _denv_dir="$(cd -- "${_run_gui_test_dir}/../../" && pwd)"
+  _denv="${_denv_dir}/denv"
+  _test_image_name="denv-gui-test-image"
 
-cd "${_run_gui_test_dir}/image"
-docker build . -t "${_test_image_name}"
+  docker_check || return $?
+
+  build_test_image \
+    "${_run_gui_test_dir}/image" \
+    "${_test_image_name}" || return $?
+
+  # need to accomodate mktemp on either GNU (left) or BSD (right)
+  test_d=$(mktemp -d 2> /dev/null || mktemp -d -t 'denv-test-gui-tmpdir')
+
+  run_gui_test \
+    "${test_d}" \
+    "${_test_image_name}" \
+    "${_denv}"
+}
 
-test_d=$(mktemp --directory)
-cd "${test_d}"
-"${_denv}" init --clean-env "${_test_image_name}:latest"
-"${_denv}" xeyes
-cd
-rm -r "${test_d}"
+main