add tests for version commands

test/version-file-read.bats

@@ -0,0 +1,39 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+setup() {
+  mkdir -p "${RBENV_TEST_DIR}/myproject"
+  cd "${RBENV_TEST_DIR}/myproject"
+}
+
+@test "fails without arguments" {
+  run rbenv-version-file-read
+  assert_failure ""
+}
+
+@test "fails for invalid file" {
+  run rbenv-version-file-read "non-existent"
+  assert_failure ""
+}
+
+@test "reads simple version file" {
+  cat > my-version <<<"1.9.3"
+  run rbenv-version-file-read my-version
+  assert_success "1.9.3"
+}
+
+@test "reads only the first word from file" {
+  cat > my-version <<<"1.9.3-p194@tag 1.8.7 hi"
+  run rbenv-version-file-read my-version
+  assert_success "1.9.3-p194@tag"
+}
+
+@test "loads only the first line in file" {
+  cat > my-version <<IN
+1.8.7 one
+1.9.3 two
+IN
+  run rbenv-version-file-read my-version
+  assert_success "1.8.7"
+}