Add metrics test

bskylink/package.json

@@ -4,7 +4,9 @@
   "type": "module",
   "main": "index.ts",
   "scripts": {
-    "test": "./tests/infra/with-test-db.sh node --loader ts-node/esm --test ./tests/index.ts",
+    "test": "npm run test:unit && npm run test:e2e",
+    "test:e2e": "./tests/infra/with-test-db.sh node --loader ts-node/esm --test ./tests/index.ts",
+    "test:unit": "node --loader ts-node/esm --test ./src/*.test.ts",
     "build": "tsc"
   },
   "dependencies": {

bskylink/src/metrics.test.ts

@@ -0,0 +1,183 @@
+import assert from 'node:assert'
+import {afterEach, beforeEach, describe, it, mock} from 'node:test'
+
+import {httpLogger} from './logger.js'
+import {MetricsClient} from './metrics.js'
+
+type TestEvents = {
+  click: {button: string}
+  view: {screen: string}
+}
+
+describe('MetricsClient', () => {
+  let fetchMock: ReturnType<typeof mock.fn>
+  let fetchRequests: {body: any}[]
+  let client: MetricsClient<TestEvents>
+  let loggerErrorMock: ReturnType<typeof mock.fn>
+
+  beforeEach(() => {
+    mock.timers.enable({apis: ['setInterval', 'setTimeout']})
+    fetchRequests = []
+    fetchMock = mock.fn(async (_url: any, options: any) => {
+      const body = JSON.parse(options.body)
+      fetchRequests.push({body})
+      return {ok: true, status: 200, text: async () => ''}
+    })
+    ;(globalThis as any).fetch = fetchMock
+    loggerErrorMock = mock.fn()
+    httpLogger.error = loggerErrorMock as any
+  })
+
+  afterEach(() => {
+    client?.stop()
+    mock.timers.reset()
+    mock.restoreAll()
+  })
+
+  it('flushes events on interval', async () => {
+    client = new MetricsClient<TestEvents>({
+      trackingEndpoint: 'https://test.metrics.api',
+    })
+    client.track('click', {button: 'submit'})
+    client.track('view', {screen: 'home'})
+
+    assert.strictEqual(fetchRequests.length, 0)
+
+    mock.timers.tick(10_000)
+    await flush()
+
+    assert.strictEqual(fetchRequests.length, 1)
+    assert.strictEqual(fetchRequests[0].body.events.length, 2)
+    assert.strictEqual(fetchRequests[0].body.events[0].event, 'click')
+    assert.strictEqual(fetchRequests[0].body.events[1].event, 'view')
+  })
+
+  it('flushes when maxBatchSize is exceeded', async () => {
+    client = new MetricsClient<TestEvents>({
+      trackingEndpoint: 'https://test.metrics.api',
+    })
+    client.maxBatchSize = 5
+
+    for (let i = 0; i < 5; i++) {
+      client.track('click', {button: `btn-${i}`})
+    }
+
+    assert.strictEqual(fetchRequests.length, 0)
+
+    client.track('click', {button: 'btn-trigger'})
+    await flush()
+
+    assert.strictEqual(fetchRequests.length, 1)
+    assert.strictEqual(fetchRequests[0].body.events.length, 6)
+  })
+
+  it('logs error on failed request', async () => {
+    fetchMock.mock.mockImplementation(async () => {
+      return {
+        ok: false,
+        status: 500,
+        text: async () => 'Internal Server Error',
+      }
+    })
+
+    client = new MetricsClient<TestEvents>({
+      trackingEndpoint: 'https://test.metrics.api',
+    })
+    client.track('click', {button: 'submit'})
+
+    mock.timers.tick(10_000)
+    await flush()
+
+    assert.strictEqual(fetchMock.mock.callCount(), 1)
+    assert.strictEqual(loggerErrorMock.mock.callCount(), 1)
+    const call = loggerErrorMock.mock.calls[0]
+    const arg = call.arguments[0] as {err: Error}
+    assert.ok(arg.err instanceof Error)
+    assert.strictEqual(call.arguments[1], 'Failed to send metrics')
+  })
+
+  it('handles fetch text() error gracefully', async () => {
+    fetchMock.mock.mockImplementation(async () => {
+      return {
+        ok: false,
+        status: 500,
+        text: async () => {
+          throw new Error('Failed to read response')
+        },
+      }
+    })
+
+    client = new MetricsClient<TestEvents>({
+      trackingEndpoint: 'https://test.metrics.api',
+    })
+    client.track('click', {button: 'submit'})
+
+    mock.timers.tick(10_000)
+    await flush()
+
+    assert.strictEqual(fetchMock.mock.callCount(), 1)
+    assert.strictEqual(loggerErrorMock.mock.callCount(), 1)
+    const call = loggerErrorMock.mock.calls[0]
+    const arg = call.arguments[0] as {err: Error}
+    assert.ok(arg.err instanceof Error)
+    assert.match(arg.err.message, /Unknown error/)
+    assert.strictEqual(call.arguments[1], 'Failed to send metrics')
+  })
+
+  it('flushes when stop() is called', async () => {
+    client = new MetricsClient<TestEvents>({
+      trackingEndpoint: 'https://test.metrics.api',
+    })
+    client.track('click', {button: 'submit'})
+
+    assert.strictEqual(fetchRequests.length, 0)
+
+    client.stop()
+    await flush()
+
+    assert.strictEqual(fetchRequests.length, 1)
+    assert.strictEqual(fetchRequests[0].body.events.length, 1)
+    assert.strictEqual(fetchRequests[0].body.events[0].event, 'click')
+  })
+
+  it('does not send if trackingEndpoint is not configured', async () => {
+    client = new MetricsClient<TestEvents>({})
+    client.track('click', {button: 'submit'})
+
+    mock.timers.tick(10_000)
+    await flush()
+
+    assert.strictEqual(fetchMock.mock.callCount(), 0)
+  })
+
+  it('start() is idempotent', async () => {
+    client = new MetricsClient<TestEvents>({
+      trackingEndpoint: 'https://test.metrics.api',
+    })
+
+    client.track('click', {button: 'submit'})
+    client.start()
+    client.start()
+
+    mock.timers.tick(10_000)
+    await flush()
+
+    assert.strictEqual(fetchRequests.length, 1)
+  })
+
+  it('does not flush if queue is empty', async () => {
+    client = new MetricsClient<TestEvents>({
+      trackingEndpoint: 'https://test.metrics.api',
+    })
+    client.start()
+
+    mock.timers.tick(10_000)
+    await flush()
+
+    assert.strictEqual(fetchMock.mock.callCount(), 0)
+  })
+})
+
+function flush() {
+  return new Promise(r => setImmediate(r))
+}