03/02(wip): add auto fixture example

Author: kettanaito

exercises/03.context/02.solution.automatic-fixtures/package.json

@@ -9,5 +9,8 @@
   "devDependencies": {
     "vite": "^6.0.7",
     "vitest": "^3.0.5"
+  },
+  "dependencies": {
+    "sqlite3": "^5.1.7"
   }
 }

exercises/03.context/02.solution.automatic-fixtures/src/db.ts

@@ -0,0 +1,19 @@
+import sqlite3, { type Database } from 'sqlite3'
+
+export class DatabaseClient {
+	constructor(private readonly db: Database) {}
+
+	public async query(query: string, params: Array<unknown>): Promise<any> {
+		return new Promise((resolve, reject) => {
+			this.db.get(query, params, function (error, row) {
+				if (error) {
+					return reject(error)
+				}
+
+				resolve(row)
+			})
+		})
+	}
+}
+
+export const client = new DatabaseClient(new sqlite3.Database(':memory:'))

exercises/03.context/02.solution.automatic-fixtures/src/example.test.ts

@@ -0,0 +1,24 @@
+import { test } from '../test-extend'
+
+test('throws if the user is not found', async () => {
+	const { queryUser } = await import('./query-user')
+
+	await expect(queryUser('abc-123')).resolves.toBeUndefined()
+})
+
+test('returns the user by id', async ({ createMockDatabase }) => {
+	const { queryUser } = await import('./query-user')
+
+	await createMockDatabase((db, done) => {
+		db.run(
+			'INSERT INTO users (id, name) VALUES (?, ?)',
+			['abc-123', 'John Doe'],
+			done,
+		)
+	})
+
+	await expect(queryUser('abc-123')).resolves.toEqual({
+		id: 'abc-123',
+		name: 'John Doe',
+	})
+})

exercises/03.context/02.solution.automatic-fixtures/src/query-user.ts

@@ -0,0 +1,10 @@
+import { client } from './db'
+
+export interface User {
+	id: string
+	name: string
+}
+
+export async function queryUser(id: string): Promise<User> {
+	return await client.query(`SELECT * FROM users WHERE id = ?`, [id])
+}

exercises/03.context/02.solution.automatic-fixtures/test-extend.ts

@@ -0,0 +1,46 @@
+import { test as testBase } from 'vitest'
+import sqlite3, { type Database } from 'sqlite3'
+
+interface Fixtures {
+	createMockDatabase: (
+		init: (database: Database, done: () => void) => void,
+	) => Promise<void>
+}
+
+export const test = testBase.extend<Fixtures>({
+	createMockDatabase: [
+		async ({ task }, use) => {
+			const db = new sqlite3.Database(':memory:')
+
+			vi.doMock(import('./src/db'), async (importOriginal) => {
+				const original = await importOriginal()
+				const mockClient = new original.DatabaseClient(db)
+
+				return {
+					...original,
+					client: mockClient,
+				}
+			})
+
+			await new Promise<void>((resolve) => {
+				db.serialize(() => {
+					db.run('CREATE TABLE users (id TEXT, name TEXT)', resolve)
+				})
+			})
+
+			await use((initDatabase) => {
+				return new Promise((resolve) => {
+					initDatabase(db, resolve)
+				})
+			})
+
+			await new Promise<void>((resolve) => {
+				db.close(() => resolve())
+			})
+			vi.doUnmock(import('./src/db'))
+		},
+		{
+			auto: true,
+		},
+	],
+})

exercises/03.context/02.solution.automatic-fixtures/tsconfig.test.json

@@ -1,6 +1,6 @@
 {
 	"extends": "./tsconfig.app.json",
-	"include": ["src/**/*", "src/**/*.test.ts*"],
+	"include": ["test-extend.ts", "src/**/*", "src/**/*.test.ts*"],
 	"exclude": [],
 	"compilerOptions": {
 		"types": ["vitest/globals"]