Merge pull request #2 from piotr-oles/feature/improve-api

feat: improve api

README.md

@@ -23,33 +23,41 @@ This package helps you with writing E2E tests for your packages.
 Example:
 
 ```typescript
-import { createSandbox, Sandbox } from "karton";
+import { 
+  createSandbox,
+  Sandbox, 
+  packLocalPackage,
+  externalPackage, 
+  Package
+} from "karton";
 import path from 'path';
-import fs from 'fs-extra';
 
 describe('my-package', () => {
   let sandbox: Sandbox;
-  beforeEach(async () => {
+  let myPackage: Package;
+
+  beforeAll(async () => {
+    myPackage = await packLocalPackage(
+      path.resolve(__dirname, '../../')
+    );
     sandbox = await createSandbox();
   });
   afterEach(async () => {
-    await sandbox.destroy();
+    await sandbox.reset();
   });
+  afterAll(async () => {
+    await sandbox.cleanup();
+    await myPackage.remove();
+  })
 
   it.each([
-    '^4.0.0',
-    '^5.0.0'
-  ])('works with webpack %p', async (webpackVersion) => {
-    const packageJSON = JSON.parse(
-      await fs.readFile('fixtures/package.json', 'utf-8')
-    );
-    packageJSON.dependencies['webpack'] = webpackVersion;
-    packageJSON.dependencies['my-package'] = path.resolve(__dirname, '../my-package-0.0.0.tgz');
-
-    await sandbox.write('package.json', JSON.stringify(packageJSON));
-    await sandbox.write('src/test.js', await fs.readFile('fixtures/src/test.js'));
-
-    await sandbox.exec('yarn install');
+    externalPackage('webpack', '^4.0.0'),
+    externalPackage('webpack', '^5.0.0')
+  ])('works with webpack %p', async (webpack) => {
+    await sandbox.load(path.join(__dirname, 'fixtures/basic'));
+    await sandbox.install('yarn', {
+      dependencies: [myPackage, webpack]
+    });
     const result = await sandbox.exec('node src/test.js');
 
     expect(result).toEqual('my-package awesome output');

src/async.ts

@@ -0,0 +1,40 @@
+import { Logger } from "./logger";
+
+function wait(timeout = 250) {
+  return new Promise((resolve) => setTimeout(resolve, timeout));
+}
+
+interface RetryOptions {
+  retries?: number;
+  delay?: number;
+}
+
+/**
+ * The IO effects sometimes fail due to different external issues - for example, network or filesystem.
+ * To make these tests more reliable, we can wrap these effects in the `retry` function.
+ */
+async function retry<T>(
+  effect: () => Promise<T>,
+  logger: Logger,
+  options: RetryOptions = {}
+): Promise<T> {
+  const retries = options.retries || 3;
+  const delay = options.delay || 250;
+
+  let lastError: unknown;
+
+  for (let retry = 1; retry <= retries; ++retry) {
+    try {
+      return await effect();
+    } catch (error) {
+      logger.log(error.toString());
+      logger.log(`Retry ${retry} of ${retries}.`);
+      lastError = error;
+      await wait(delay);
+    }
+  }
+
+  throw lastError;
+}
+
+export { wait, retry, RetryOptions };