add tests for version commands

test/version.bats

@@ -0,0 +1,38 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+create_version() {
+  mkdir -p "${RBENV_ROOT}/versions/$1"
+}
+
+setup() {
+  mkdir -p "$RBENV_TEST_DIR"
+  cd "$RBENV_TEST_DIR"
+}
+
+@test "no version selected" {
+  assert [ ! -d "${RBENV_ROOT}/versions" ]
+  run rbenv-version
+  assert_success "system (set by ${RBENV_ROOT}/version)"
+}
+
+@test "set by RBENV_VERSION" {
+  create_version "1.9.3"
+  RBENV_VERSION=1.9.3 run rbenv-version
+  assert_success "1.9.3 (set by RBENV_VERSION environment variable)"
+}
+
+@test "set by local file" {
+  create_version "1.9.3"
+  cat > ".ruby-version" <<<"1.9.3"
+  run rbenv-version
+  assert_success "1.9.3 (set by ${PWD}/.ruby-version)"
+}
+
+@test "set by global file" {
+  create_version "1.9.3"
+  cat > "${RBENV_ROOT}/version" <<<"1.9.3"
+  run rbenv-version
+  assert_success "1.9.3 (set by ${RBENV_ROOT}/version)"
+}