Fix blueprint tests

Author: dfreeman

ts/tests/blueprints/ember-cli-typescript-test.ts

@@ -6,12 +6,15 @@ import helpers from 'ember-cli-blueprint-test-helpers/helpers';
 import chaiHelpers from 'ember-cli-blueprint-test-helpers/chai';
 import Blueprint from 'ember-cli/lib/models/blueprint';
 
+import { setupPublishedVersionStashing } from '../helpers/stash-published-version';
 import ects from '../../blueprints/ember-cli-typescript/index';
 
 const expect = chaiHelpers.expect;
 const file = chaiHelpers.file;
 
 describe('Acceptance: ember-cli-typescript generator', function () {
+  setupPublishedVersionStashing(this);
+
   helpers.setupTestHooks(this, {
     disabledTasks: ['addon-install', 'bower-install'],
   });

ts/tests/helpers/stash-published-version.ts

@@ -0,0 +1,21 @@
+import fs from 'fs-extra';
+
+const PACKAGE_PATH = 'node_modules/ember-cli-typescript';
+
+/**
+ * We have assorted devDependencies that themselves depend on `ember-cli-typescript`.
+ * This means we have a published copy of the addon present in `node_modules` normally,
+ * though `ember-cli-blueprint-test-helpers` fiddles around in there as well.
+ *
+ * This helper ensures we move the published version of the addon out of the way into
+ * an inert location during the enclosing `describe` block and put it back afterwards.
+ */
+export function setupPublishedVersionStashing(hooks: Mocha.Suite): void {
+  hooks.beforeAll(async () => {
+    await fs.move(PACKAGE_PATH, `${PACKAGE_PATH}.published`);
+  });
+
+  hooks.afterAll(async () => {
+    await fs.move(`${PACKAGE_PATH}.published`, PACKAGE_PATH);
+  });
+}