Add jest metrics (#2897)

* Add slow jest reporter

spec/slowReporter.js

@@ -0,0 +1,100 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+/* eslint-disable no-console */
+
+class JestSlowTestReporter {
+    constructor(globalConfig, options) {
+        this._globalConfig = globalConfig;
+        this._options = options;
+        this._slowTests = [];
+        this._slowTestSuites = [];
+    }
+
+    onRunComplete() {
+        const displayResult = (result, isTestSuite) => {
+            if (!isTestSuite) console.log();
+
+            result.sort((a, b) => b.duration - a.duration);
+            const rootPathRegex = new RegExp(`^${process.cwd()}`);
+            const slowestTests = result.slice(0, this._options.numTests || 10);
+            const slowTestTime = this._slowTestTime(slowestTests);
+            const allTestTime = this._allTestTime(result);
+            const percentTime = (slowTestTime / allTestTime) * 100;
+
+            if (isTestSuite) {
+                console.log(
+                    `Top ${slowestTests.length} slowest test suites (${slowTestTime / 1000} seconds,` +
+              ` ${percentTime.toFixed(1)}% of total time):`,
+                );
+            } else {
+                console.log(
+                    `Top ${slowestTests.length} slowest tests (${slowTestTime / 1000} seconds,` +
+              ` ${percentTime.toFixed(1)}% of total time):`,
+                );
+            }
+
+            for (let i = 0; i < slowestTests.length; i++) {
+                const duration = slowestTests[i].duration;
+                const filePath = slowestTests[i].filePath.replace(rootPathRegex, '.');
+
+                if (isTestSuite) {
+                    console.log(`  ${duration / 1000} seconds ${filePath}`);
+                } else {
+                    const fullName = slowestTests[i].fullName;
+                    console.log(`  ${fullName}`);
+                    console.log(`    ${duration / 1000} seconds ${filePath}`);
+                }
+            }
+            console.log();
+        };
+
+        displayResult(this._slowTests);
+        displayResult(this._slowTestSuites, true);
+    }
+
+    onTestResult(test, testResult) {
+        this._slowTestSuites.push({
+            duration: testResult.perfStats.runtime,
+            filePath: testResult.testFilePath,
+        });
+        for (let i = 0; i < testResult.testResults.length; i++) {
+            this._slowTests.push({
+                duration: testResult.testResults[i].duration,
+                fullName: testResult.testResults[i].fullName,
+                filePath: testResult.testFilePath,
+            });
+        }
+    }
+
+    _slowTestTime(slowestTests) {
+        let slowTestTime = 0;
+        for (let i = 0; i < slowestTests.length; i++) {
+            slowTestTime += slowestTests[i].duration;
+        }
+        return slowTestTime;
+    }
+
+    _allTestTime(result) {
+        let allTestTime = 0;
+        for (let i = 0; i < result.length; i++) {
+            allTestTime += result[i].duration;
+        }
+        return allTestTime;
+    }
+}
+
+module.exports = JestSlowTestReporter;