chore: continue with testing

Author: lmammino

10-testing/13-unit-test-mock-other-modules/README.md

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+# 13-unit-test-mock-other-modules
+
+Demonstrates how to mock internal or third-party modules
+
+## Run
+
+To run the example launch:
+
+```
+node --test  --experimental-test-module-mocks
+```

10-testing/13-unit-test-mock-other-modules/dbClient.js

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+export class DbClient {
+  // biome-ignore lint/suspicious/useAwait: just for demonstration
+  async query(_sql, _params) {
+    // In real life, this would talk to a database
+    throw new Error('Not implemented')
+  }
+}

10-testing/13-unit-test-mock-other-modules/package.json

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+{
+  "name": "13-unit-test-mock-other-modules",
+  "version": "1.0.0",
+  "description": "Demonstrates how to mock internal or third-party modules",
+  "type": "module",
+  "scripts": {},
+  "engines": {
+    "node": ">=22"
+  },
+  "engineStrict": true,
+  "keywords": [],
+  "author": "Luciano Mammino and Mario Casciaro",
+  "license": "MIT",
+  "dependencies": {}
+}

10-testing/13-unit-test-mock-other-modules/payments.js

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+import { DbClient } from './dbClient.js'
+
+const db = new DbClient()
+
+export async function canPayWithVouchers(userId, amount) {
+  const vouchers = await db.query(
+    `SELECT * FROM vouchers 
+       WHERE user_id = ? AND 
+       balance > 0 AND
+       expiresAt > NOW()`,
+    [userId]
+  )
+
+  const availableBalance = vouchers.reduce((acc, v) => acc + v.balance, 0)
+
+  return availableBalance >= amount
+}

10-testing/13-unit-test-mock-other-modules/payments.test.js

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+import assert from 'node:assert/strict'
+import { after, beforeEach, mock, suite, test } from 'node:test'
+import { setImmediate } from 'node:timers/promises'
+
+const sampleRecords = [
+  {
+    id: 1,
+    userId: 'user1',
+    balance: 10,
+    expiresAt: new Date(Date.now() + 1000),
+  },
+  {
+    id: 2,
+    userId: 'user1',
+    balance: 5,
+    expiresAt: new Date(Date.now() + 1000),
+  },
+  {
+    id: 3,
+    userId: 'user1',
+    balance: 3,
+    expiresAt: new Date(Date.now() + 1000),
+  },
+]
+
+const queryMock = mock.fn(async (_sql, _params) => {
+  await setImmediate()
+  return sampleRecords
+})
+
+mock.module('./dbClient.js', {
+  cache: false,
+  namedExports: {
+    // biome-ignore lint/style/useNamingConvention: <explanation>
+    DbClient: class DbMock {
+      query = queryMock
+    },
+  },
+})
+
+const { canPayWithVouchers } = await import('./payments.js')
+
+suite('canPayWithVouchers', { concurrency: false, timeout: 500 }, () => {
+  beforeEach(() => {
+    queryMock.mock.resetCalls()
+  })
+
+  after(() => {
+    queryMock.mock.restore()
+  })
+
+  test('Returns true if balance is enough', async () => {
+    const result = await canPayWithVouchers('user1', 18)
+
+    assert.equal(result, true)
+    assert.equal(queryMock.mock.callCount(), 1)
+  })
+
+  test('Returns false if balance is not enough', async () => {
+    const result = await canPayWithVouchers('user1', 19)
+
+    assert.equal(result, false)
+    assert.equal(queryMock.mock.callCount(), 1)
+  })
+})

10-testing/14-unit-test-dependency-injection/README.md

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+# 13-unit-test-mock-other-modules
+
+Demonstrates how to mock internal or third-party modules
+
+## Run
+
+To run the example launch:
+
+```
+node --test  --experimental-test-module-mocks
+```

10-testing/14-unit-test-dependency-injection/dbClient.js

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+export class DbClient {
+  // biome-ignore lint/suspicious/useAwait: just for demonstration
+  async query(_sql, _params) {
+    // In real life, this would talk to a database
+    throw new Error('Not implemented')
+  }
+}

10-testing/14-unit-test-dependency-injection/package.json

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+{
+  "name": "13-unit-test-mock-other-modules",
+  "version": "1.0.0",
+  "description": "Demonstrates how to mock internal or third-party modules",
+  "type": "module",
+  "scripts": {},
+  "engines": {
+    "node": ">=22"
+  },
+  "engineStrict": true,
+  "keywords": [],
+  "author": "Luciano Mammino and Mario Casciaro",
+  "license": "MIT",
+  "dependencies": {}
+}

10-testing/14-unit-test-dependency-injection/payments.js

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+export async function canPayWithVouchers(db, userId, amount) {
+  const vouchers = await db.query(
+    `SELECT * FROM vouchers 
+       WHERE user_id = ? AND 
+       balance > 0 AND
+       expiresAt > NOW()`,
+    [userId]
+  )
+
+  const availableBalance = vouchers.reduce((acc, v) => acc + v.balance, 0)
+
+  return availableBalance >= amount
+}

10-testing/14-unit-test-dependency-injection/payments.test.js

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+import assert from 'node:assert/strict'
+import { suite, test } from 'node:test'
+import { setImmediate } from 'node:timers/promises'
+import { canPayWithVouchers } from './payments.js'
+
+const sampleRecords = [
+  {
+    id: 1,
+    userId: 'user1',
+    balance: 10,
+    expiresAt: new Date(Date.now() + 1000),
+  },
+  {
+    id: 2,
+    userId: 'user1',
+    balance: 5,
+    expiresAt: new Date(Date.now() + 1000),
+  },
+  {
+    id: 3,
+    userId: 'user1',
+    balance: 3,
+    expiresAt: new Date(Date.now() + 1000),
+  },
+]
+
+suite('canPayWithVouchers', { concurrency: true, timeout: 500 }, () => {
+  test('Returns true if balance is enough', async t => {
+    const dbMock = {
+      query: t.mock.fn(async (_sql, _params) => {
+        await setImmediate()
+        return sampleRecords
+      }),
+    }
+
+    const result = await canPayWithVouchers(dbMock, 'user1', 18)
+
+    assert.equal(result, true)
+    assert.equal(dbMock.query.mock.callCount(), 1)
+  })
+
+  test('Returns false if balance is not enough', async t => {
+    const dbMock = {
+      query: t.mock.fn(async (_sql, _params) => {
+        await setImmediate()
+        return sampleRecords
+      }),
+    }
+
+    const result = await canPayWithVouchers(dbMock, 'user1', 19)
+
+    assert.equal(result, false)
+    assert.equal(dbMock.query.mock.callCount(), 1)
+  })
+})