Robust test env setup

The test environment needs an isolated NODENV_ROOT, an unaltered
NODENV_VERSION, nodenv to be in PATH (from npm), for the plugin under
test to be in PATH, and for the plugin under test's hooks to be in
NODENV_HOOK_PATH.

An alternative would be to just symlink the plugin under test into a
dummy NODENV_ROOT/plugins. However, that's much slower than just setting
the env vars. Further, the explicit variables more clearly document
what's necessary for a plugin integration.

Author: jasonkarns

test/nodenv-package-json-engine.bats

@@ -86,6 +86,7 @@ load test_helper
 }
 
 @test 'Does not match babel preset env settings' {
+  create_version 4.2.1
   cd_into_babel_env_package
   run nodenv version-name
   assert_success 'system'

test/test_helper.bash

@@ -3,17 +3,20 @@
 load ../node_modules/bats-assert/all
 
 setup() {
+  # common nodenv setup
   unset NODENV_VERSION
 
-  EXAMPLE_PACKAGE_DIR="$BATS_TMPDIR/example_package"
+  local node_modules_bin=$BATS_TEST_DIRNAME/../node_modules/.bin
+  local plugin_bin=$BATS_TEST_DIRNAME/../bin
+
+  export PATH="$plugin_bin:$node_modules_bin:/usr/bin:/bin:/usr/sbin:/sbin"
 
   export NODENV_ROOT="$BATS_TMPDIR/nodenv_root"
+  export NODENV_HOOK_PATH="$BATS_TEST_DIRNAME/../etc/nodenv.d"
 
-  PATH="$(npm bin):/usr/bin:/bin:/usr/sbin:/sbin"
-  PATH="${BATS_TEST_DIRNAME}/../bin:$PATH"
-  export PATH
+  # unique
 
-  eval "$(nodenv init -)"
+  EXAMPLE_PACKAGE_DIR="$BATS_TMPDIR/example_package"
 }
 
 teardown() {