add tests for version commands

test/version-origin.bats

@@ -0,0 +1,38 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+setup() {
+  mkdir -p "$RBENV_TEST_DIR"
+  cd "$RBENV_TEST_DIR"
+}
+
+@test "reports global file even if it doesn't exist" {
+  assert [ ! -e "${RBENV_ROOT}/version" ]
+  run rbenv-version-origin
+  assert_success "${RBENV_ROOT}/version"
+}
+
+@test "detects global file" {
+  mkdir -p "$RBENV_ROOT"
+  touch "${RBENV_ROOT}/version"
+  run rbenv-version-origin
+  assert_success "${RBENV_ROOT}/version"
+}
+
+@test "detects RBENV_VERSION" {
+  RBENV_VERSION=1 run rbenv-version-origin
+  assert_success "RBENV_VERSION environment variable"
+}
+
+@test "detects local file" {
+  touch .ruby-version
+  run rbenv-version-origin
+  assert_success "${PWD}/.ruby-version"
+}
+
+@test "detects alternate version file" {
+  touch .rbenv-version
+  run rbenv-version-origin
+  assert_success "${PWD}/.rbenv-version"
+}