03/03: add solution

Author: kettanaito

exercises/03.context/03.solution.global-context/README.mdx

@@ -1,3 +1 @@
 # Global context
-
-- Show how to expose the custom `test` function globally instead of importing it everywhere.

exercises/03.context/03.solution.global-context/package.json

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

exercises/03.context/03.solution.global-context/src/database.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/03.solution.global-context/src/example.test.ts

@@ -0,0 +1,20 @@
+import { queryUser } from './query-user'
+
+test('throws if the user is not found', async () => {
+	await expect(queryUser('abc-123')).resolves.toBeUndefined()
+})
+
+test('returns the user by id', async ({ createMockDatabase }) => {
+	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/03.solution.global-context/src/query-user.ts

@@ -0,0 +1,10 @@
+import { client } from './database'
+
+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/03.solution.global-context/test-extend.ts

@@ -0,0 +1,85 @@
+import * as fs from 'node:fs'
+import * as path from 'node:path'
+import { test as testBase } from 'vitest'
+import sqlite3, { type Database } from 'sqlite3'
+import * as databaseModule from './src/database'
+
+interface Fixtures {
+	createMockDatabase: (
+		seed: (database: Database, handle: CallbackHandle) => void,
+	) => Promise<void>
+}
+
+declare module 'vitest' {
+	export interface TestContext extends Fixtures {}
+}
+
+declare namespace globalThis {
+	var test: typeof testBase
+}
+
+type CallbackHandle = (error?: Error | null, ...args: Array<any>) => void
+
+function toPromise<T>(init: (handle: CallbackHandle) => T): Promise<T> {
+	return new Promise<T>((resolve, reject) => {
+		const result = init((error) => {
+			if (error) {
+				return reject(error)
+			}
+			resolve(result)
+		})
+	})
+}
+
+globalThis.test = testBase.extend<Fixtures>({
+	createMockDatabase: [
+		async ({ task, onTestFinished }, use) => {
+			const dbFile = `${task.file.filepath}-${task.id}.sqlite`
+
+			if (fs.existsSync(dbFile)) {
+				await fs.promises.rm(dbFile)
+			}
+
+			const mockDatabase = await toPromise((handle) => {
+				return new sqlite3.Database(dbFile, handle)
+			})
+
+			onTestFinished(async ({ task }) => {
+				await toPromise((handle) => mockDatabase.close(handle))
+
+				if (task.type !== 'test') {
+					return
+				}
+
+				if (task.result?.state === 'pass') {
+					await fs.promises.rm(dbFile)
+				} else {
+					task.result?.errors?.push({
+						name: 'Mock database',
+						message: 'See the database state:',
+						codeFrame: path.relative(process.cwd(), dbFile),
+					})
+				}
+			})
+
+			const clientSpy = vi
+				.spyOn(databaseModule, 'client', 'get')
+				.mockReturnValue(new databaseModule.DatabaseClient(mockDatabase))
+
+			await toPromise((handle) => {
+				mockDatabase.run('CREATE TABLE users (id TEXT, name TEXT)', handle)
+			})
+
+			await use((seed) => {
+				return toPromise((handle) => {
+					seed(mockDatabase, handle)
+				})
+			})
+
+			clientSpy.mockRestore()
+		},
+		{
+			auto: true,
+		},
+	],
+})

exercises/03.context/03.solution.global-context/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"]

exercises/03.context/03.solution.global-context/vite.config.ts

@@ -7,5 +7,6 @@ export default defineConfig({
 	},
 	test: {
 		globals: true,
+		setupFiles: ['./test-extend.ts'],
 	},
 })