Add examples

README.md

@@ -11,7 +11,8 @@ $ npm i -D @mizdra/inline-fixture-files
 ## Features
 
 - Write fixture files inline
-- TypeScript support
+- Type-safe access to the fixture file path
+- Share fixture files between test cases
 - Cross-platform support
 - Zero dependencies
 
@@ -32,7 +33,54 @@ However, this approach leads to the test code and fixture file definitions being
 
 `@mizdra/inline-fixture-files` allows you to define fixture files in your test code. This makes the test code easier to understand.
 
-```typescript
+```ts
+import dedent from 'dedent';
+import { createIFF } from '@mizdra/inline-fixture-files';
+
+const iff1 = await createIFF(
+  {
+    'src/index.ts': dedent`
+      export function hello() {
+        console.log('Hello, world!');
+      }
+    `,
+  },
+  { rootDir: join(fixtureDir, 'test-case-1') },
+);
+const iff2 = await createIFF(
+  {
+    src: {
+      'index.ts': dedent`
+        import { add } from './math';
+
+        export function hello() {
+          console.log('Hello, world!');
+          console.log(add(1, 2));
+        }
+      `,
+      'math.ts': dedent`
+        export function add(a: number, b: number): number {
+          return a + b;
+        }
+      `,
+    },
+  },
+  { rootDir: join(fixtureDir, 'test-case-1') },
+);
+```
+
+## API documentation
+
+See [/docs/api/index.md](/docs/api/index.md).
+
+## Examples
+
+### Example: Basic
+
+You can use `iff.paths` to get the paths of the generated fixture files.
+
+```ts
+// example/01-basic.test.ts
 import { rm } from 'node:fs/promises';
 import { tmpdir } from 'node:os';
 import { join } from 'node:path';
@@ -75,6 +123,124 @@ test('eslint reports lint errors', async () => {
 });
 ```
 
-## API documentation
+### Example: Random `roodDir`
 
-See [/docs/api/index.md](/docs/api/index.md).
+If you use `@mizdra/inline-fixture-files`, it is recommended to create a utility (`createIFFByRandomRootDir`) that generates a random `rootDir` and calls `createIFF` with it. This is very helpful to keep each test case independent.
+
+````ts
+// example/util/create-iff-by-random-root-dir.js
+import { randomUUID } from 'node:crypto';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { createIFF, Directory } from '@mizdra/inline-fixture-files';
+/**
+ * The root directory for fixtures.
+ *
+ * NOTE: To avoid bloating `fixtureDir`, it is recommended to delete `fixtureDir` at the beginning of the test.
+ * ```ts
+ * // vitest.setup.ts
+ * import { rm } from 'node:fs/promises';
+ * await rm(fixtureDir, { recursive: true, force: true });
+ * ```
+ */
+// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+const fixtureDir = join(tmpdir(), 'inline-fs-fixtures', process.env['VITEST_POOL_ID']!);
+
+export async function createIFFByRandomRootDir<const T extends Directory>(directory: T) {
+  const getRandomRootDir = () => join(fixtureDir, randomUUID());
+  const iff = await createIFF(directory, { rootDir: getRandomRootDir() });
+  return {
+    ...iff,
+    fork: async function forkImpl<const U extends Directory>(additionalDirectory: U) {
+      const forkedIff = await iff.fork(additionalDirectory, { rootDir: getRandomRootDir() });
+      return { ...forkedIff, fork: forkImpl };
+    },
+  };
+}
+````
+
+```ts
+// example/02-random-root-dir.test.ts
+import dedent from 'dedent';
+import { ESLint } from 'eslint';
+import { expect, test } from 'vitest';
+import { createIFFByRandomRootDir } from './util/create-iff-by-random-root-dir.js';
+
+test('eslint reports lint errors', async () => {
+  const iff = await createIFFByRandomRootDir({
+    '.eslintrc.cjs': `module.exports = { root: true, rules: { semi: 'error' } };`,
+    'src': {
+      'semi.js': dedent`
+        var withSemicolon = 1;
+        var withoutSemicolon = 2
+      `,
+    },
+  });
+
+  const eslint = new ESLint({ cwd: iff.rootDir, useEslintrc: true });
+  const results = await eslint.lintFiles([iff.paths['src/semi.js']]);
+  const formatter = await eslint.loadFormatter('unix');
+  const resultText = formatter.format(results);
+  expect(resultText).toStrictEqual(dedent`
+    ${iff.paths['src/semi.js']}:2:25: Missing semicolon. [Error/semi]
+
+    1 problem
+  `);
+});
+```
+
+### Example: Share fixture files between test cases
+
+`iff.fork` is an API that changes the root directory while taking over previously created fixture files. It allows fixture files to be shared between test cases.
+
+```ts
+// example/03-share-fixtures-between-test-cases.test.ts
+import { readFile } from 'node:fs/promises';
+import dedent from 'dedent';
+import { ESLint } from 'eslint';
+import { describe, expect, it } from 'vitest';
+import { createIFFByRandomRootDir } from './util/create-iff-by-random-root-dir.js';
+
+describe('eslint', async () => {
+  // Share `.eslintrc.cjs` between test cases.
+  const baseIFF = await createIFFByRandomRootDir({
+    '.eslintrc.cjs': `module.exports = { root: true, rules: { semi: 'error' } };`,
+  });
+
+  it('reports lint errors', async () => {
+    // The `fork` allows you to change the `rootDir` of fixtures while inheriting the fixtures from `baseIFF`.
+    const iff = await baseIFF.fork({
+      src: {
+        'semi.js': dedent`
+          var withSemicolon = 1;
+          var withoutSemicolon = 2
+        `,
+      },
+    });
+    const eslint = new ESLint({ cwd: iff.rootDir, useEslintrc: true });
+    const results = await eslint.lintFiles([iff.paths['src/semi.js']]);
+    const formatter = await eslint.loadFormatter('unix');
+    const resultText = formatter.format(results);
+    expect(resultText).toStrictEqual(dedent`
+      ${iff.paths['src/semi.js']}:2:25: Missing semicolon. [Error/semi]
+
+      1 problem
+    `);
+  });
+  it('fix lint errors', async () => {
+    const iff = await baseIFF.fork({
+      src: {
+        'semi.js': dedent`
+          var withoutSemicolon = 2
+        `,
+      },
+    });
+    const eslint = new ESLint({ cwd: iff.rootDir, useEslintrc: true, fix: true });
+    const results = await eslint.lintFiles([iff.paths['src/semi.js']]);
+
+    expect(await readFile(iff.paths['src/semi.js'], 'utf8')).toMatchInlineSnapshot('"var withoutSemicolon = 2"');
+    await ESLint.outputFixes(results);
+    expect(await readFile(iff.paths['src/semi.js'], 'utf8')).toMatchInlineSnapshot('"var withoutSemicolon = 2;"');
+  });
+});
+```

example/02-random-root-dir.test.ts

@@ -0,0 +1,26 @@
+import dedent from 'dedent';
+import { ESLint } from 'eslint';
+import { expect, test } from 'vitest';
+import { createIFFByRandomRootDir } from './util/create-iff-by-random-root-dir.js';
+
+test('eslint reports lint errors', async () => {
+  const iff = await createIFFByRandomRootDir({
+    '.eslintrc.cjs': `module.exports = { root: true, rules: { semi: 'error' } };`,
+    'src': {
+      'semi.js': dedent`
+        var withSemicolon = 1;
+        var withoutSemicolon = 2
+      `,
+    },
+  });
+
+  const eslint = new ESLint({ cwd: iff.rootDir, useEslintrc: true });
+  const results = await eslint.lintFiles([iff.paths['src/semi.js']]);
+  const formatter = await eslint.loadFormatter('unix');
+  const resultText = formatter.format(results);
+  expect(resultText).toStrictEqual(dedent`
+    ${iff.paths['src/semi.js']}:2:25: Missing semicolon. [Error/semi]
+
+    1 problem
+  `);
+});

example/03-share-fixtures-between-test-cases.test.ts

@@ -0,0 +1,48 @@
+import { readFile } from 'node:fs/promises';
+import dedent from 'dedent';
+import { ESLint } from 'eslint';
+import { describe, expect, it } from 'vitest';
+import { createIFFByRandomRootDir } from './util/create-iff-by-random-root-dir.js';
+
+describe('eslint', async () => {
+  // Share `.eslintrc.cjs` between test cases.
+  const baseIFF = await createIFFByRandomRootDir({
+    '.eslintrc.cjs': `module.exports = { root: true, rules: { semi: 'error' } };`,
+  });
+
+  it('reports lint errors', async () => {
+    // The `fork` allows you to change the `rootDir` of fixtures while inheriting the fixtures from `baseIFF`.
+    const iff = await baseIFF.fork({
+      src: {
+        'semi.js': dedent`
+          var withSemicolon = 1;
+          var withoutSemicolon = 2
+        `,
+      },
+    });
+    const eslint = new ESLint({ cwd: iff.rootDir, useEslintrc: true });
+    const results = await eslint.lintFiles([iff.paths['src/semi.js']]);
+    const formatter = await eslint.loadFormatter('unix');
+    const resultText = formatter.format(results);
+    expect(resultText).toStrictEqual(dedent`
+      ${iff.paths['src/semi.js']}:2:25: Missing semicolon. [Error/semi]
+
+      1 problem
+    `);
+  });
+  it('fix lint errors', async () => {
+    const iff = await baseIFF.fork({
+      src: {
+        'semi.js': dedent`
+          var withoutSemicolon = 2
+        `,
+      },
+    });
+    const eslint = new ESLint({ cwd: iff.rootDir, useEslintrc: true, fix: true });
+    const results = await eslint.lintFiles([iff.paths['src/semi.js']]);
+
+    expect(await readFile(iff.paths['src/semi.js'], 'utf8')).toMatchInlineSnapshot('"var withoutSemicolon = 2"');
+    await ESLint.outputFixes(results);
+    expect(await readFile(iff.paths['src/semi.js'], 'utf8')).toMatchInlineSnapshot('"var withoutSemicolon = 2;"');
+  });
+});

example/util/create-iff-by-random-root-dir.ts

@@ -0,0 +1,28 @@
+import { randomUUID } from 'node:crypto';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { createIFF, Directory } from '../../src/index.js';
+/**
+ * The root directory for fixtures.
+ *
+ * NOTE: To avoid bloating `fixtureDir`, it is recommended to delete `fixtureDir` at the beginning of the test.
+ * ```ts
+ * // vitest.setup.ts
+ * import { rm } from 'node:fs/promises';
+ * await rm(fixtureDir, { recursive: true, force: true });
+ * ```
+ */
+// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+const fixtureDir = join(tmpdir(), 'inline-fs-fixtures', process.env['VITEST_POOL_ID']!);
+
+export async function createIFFByRandomRootDir<const T extends Directory>(directory: T) {
+  const getRandomRootDir = () => join(fixtureDir, randomUUID());
+  const iff = await createIFF(directory, { rootDir: getRandomRootDir() });
+  return {
+    ...iff,
+    fork: async function forkImpl<const U extends Directory>(additionalDirectory: U) {
+      const forkedIff = await iff.fork(additionalDirectory, { rootDir: getRandomRootDir() });
+      return { ...forkedIff, fork: forkImpl };
+    },
+  };
+}