Add tests for `rbenv install/uninstall` hooks

test/hooks.bats

+#!/usr/bin/env bats
+
+load test_helper
+
+setup() {
+  export RBENV_ROOT="${TMP}/rbenv"
+  export HOOK_PATH="${TMP}/i has hooks"
+  mkdir -p "$HOOK_PATH"
+}
+
+@test "rbenv-install hooks" {
+  cat > "${HOOK_PATH}/install.bash" <<OUT
+before_install 'echo before: \$PREFIX'
+after_install 'echo after: \$STATUS'
+OUT
+  stub rbenv-hooks "install : echo '$HOOK_PATH'/install.bash"
+  stub rbenv-rehash "echo rehashed"
+
+  definition="${TMP}/2.0.0"
+  cat > "$definition" <<<"echo ruby-build"
+  run rbenv-install "$definition"
+
+  assert_success
+  assert_output <<-OUT
+before: ${RBENV_ROOT}/versions/2.0.0
+ruby-build
+after: 0
+rehashed
+OUT
+}
+
+@test "rbenv-uninstall hooks" {
+  cat > "${HOOK_PATH}/uninstall.bash" <<OUT
+before_uninstall 'echo before: \$PREFIX'
+after_uninstall 'echo after.'
+rm() {
+  echo "rm \$@"
+  command rm "\$@"
+}
+OUT
+  stub rbenv-hooks "uninstall : echo '$HOOK_PATH'/uninstall.bash"
+  stub rbenv-rehash "echo rehashed"
+
+  mkdir -p "${RBENV_ROOT}/versions/2.0.0"
+  run rbenv-uninstall -f 2.0.0
+
+  assert_success
+  assert_output <<-OUT
+before: ${RBENV_ROOT}/versions/2.0.0
+rm -rf ${RBENV_ROOT}/versions/2.0.0
+rehashed
+after.
+OUT
+
+  assert [ ! -d "${RBENV_ROOT}/versions/2.0.0" ]
+}