[APM] API Snapshot Testing

x-pack/test/apm_api_integration/basic/tests/index.ts

@@ -4,9 +4,13 @@
  * you may not use this file except in compliance with the Elastic License.
  */
 import { FtrProviderContext } from '../../common/ftr_provider_context';
+import * as matchSnapshot from '../../common/match_snapshot';
 
 export default function apmApiIntegrationTests({ loadTestFile }: FtrProviderContext) {
   describe('APM specs (basic)', function () {
+    beforeEach(matchSnapshot.init);
+    afterEach(matchSnapshot.teardown);
+
     this.tags('ciGroup1');
 
     loadTestFile(require.resolve('./feature_controls'));

x-pack/test/apm_api_integration/basic/tests/traces/top_traces.ts

@@ -5,6 +5,7 @@
  */
 import expect from '@kbn/expect';
 import { sortBy, omit } from 'lodash';
+import { expectToMatchSnapshot } from '../../../common/match_snapshot';
 import { FtrProviderContext } from '../../../../common/ftr_provider_context';
 import expectTopTraces from './expectation/top_traces.expectation.json';
 
@@ -19,13 +20,13 @@ export default function ApiTest({ getService }: FtrProviderContext) {
 
   describe('Top traces', () => {
     describe('when data is not loaded ', () => {
-      it('handles empty state', async () => {
+      it('handles empty state', async function () {
         const response = await supertest.get(
           `/api/apm/traces?start=${start}&end=${end}&uiFilters=${uiFilters}`
         );
 
         expect(response.status).to.be(200);
-        expect(response.body).to.eql({ items: [], isAggregationAccurate: true, bucketSize: 1000 });
+        expectToMatchSnapshot(response.body);
       });
     });
 

x-pack/test/apm_api_integration/common/match_snapshot.ts

@@ -0,0 +1,61 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import { SnapshotState, toMatchSnapshot } from 'jest-snapshot';
+import path from 'path';
+import { Context } from 'mocha';
+import expect from '@kbn/expect';
+
+let testContext: { file: string; testTitle: string } | null = null;
+
+export function init() {
+  // @ts-ignore
+  const mochaContext = this as Context;
+  const file = mochaContext.currentTest?.file;
+  const testTitle = mochaContext.currentTest?.fullTitle();
+
+  if (!file || !testTitle) {
+    throw new Error(`file or fullTitle not found in Mocha test context`);
+  }
+
+  testContext = {
+    file,
+    testTitle,
+  };
+}
+
+export function teardown() {
+  testContext = null;
+}
+
+export function expectToMatchSnapshot(actual: any) {
+  if (!testContext) {
+    throw new Error('A current Mocha context is needed to match snapshots');
+  }
+
+  const { file, testTitle } = testContext;
+
+  const dirname = path.dirname(file);
+  const filename = path.basename(file);
+
+  const snapshotState = new SnapshotState(
+    path.join(dirname + `/__snapshots__/` + filename.replace(path.extname(filename), '.snap')),
+    // not passing babel or prettier
+    // @ts-ignore
+    {
+      updateSnapshot: process.env.UPDATE_APM_SNAPSHOTS ? 'all' : 'new',
+    }
+  );
+
+  // not passing assertions
+  // @ts-ignore
+  const matcher = toMatchSnapshot.bind({ snapshotState, currentTestName: testTitle });
+  const result = matcher(actual);
+
+  snapshotState.save();
+
+  return expect(result.pass).to.eql(true, result.message());
+}