feat(mocha): deprecate mocha < v6 (#2379)

BREAKING CHANGE: Mocha@<6 is deprecated and support for it will be removed in Stryker v5

e2e/test/mocha-old-version/package.json

@@ -0,0 +1,24 @@
+{
+  "name": "mocha-old-version",
+  "version": "0.0.0",
+  "private": true,
+  "description": "A test package for mocha 5",
+  "main": "index.js",
+  "scripts": {
+    "pretest": "rimraf \"reports\"",
+    "test": "stryker run",
+    "posttest": "mocha --no-config --require ../../tasks/ts-node-register.js verify/*.ts"
+  },
+  "localDependencies": {
+    "@stryker-mutator/api": "../../../packages/api",
+    "@stryker-mutator/core": "../../../packages/core",
+    "@stryker-mutator/instrumenter": "../../../packages/instrumenter",
+    "@stryker-mutator/mocha-runner": "../../../packages/mocha-runner",
+    "@stryker-mutator/util": "../../../packages/util"
+  },
+  "author": "",
+  "license": "ISC",
+  "devDependencies": {
+    "mocha": "^5.2.0"
+  }
+}

e2e/test/mocha-old-version/src/add.js

@@ -0,0 +1,6 @@
+module.exports.add = function(num1, num2) {
+  return num1 + num2;
+};
+
+
+

e2e/test/mocha-old-version/stryker.conf.json

@@ -0,0 +1,14 @@
+{
+  "$schema": "../../node_modules/@stryker-mutator/core/schema/stryker-schema.json",
+  "testRunner": "mocha",
+  "concurrency": 1,
+  "coverageAnalysis": "off",
+  "reporters": ["clear-text", "html", "event-recorder"],
+  "mochaOptions": {
+    "spec": ["test/**/*.js"]
+  },
+  "fileLogLevel": "info",
+  "plugins": [
+    "@stryker-mutator/mocha-runner"
+  ]
+}

e2e/test/mocha-old-version/test/unit/add.spec.js

@@ -0,0 +1,10 @@
+const { add } = require('../../src/add');
+const { expect } = require('chai');
+
+describe('add', () => {
+
+  it('2 + 3 = 5', () => {
+    expect(add(2, 3)).to.be.equal(5);
+  });
+
+});

e2e/test/mocha-old-version/verify/verify.ts

@@ -0,0 +1,17 @@
+import { promises as fs } from 'fs';
+import { expect } from 'chai';
+import { it } from 'mocha';
+
+describe('Verify stryker runs with mocha < 6', () => {
+
+  let strykerLog: string;
+
+  before(async () => {
+    strykerLog = await fs.readFile('./stryker.log', 'utf8');
+  });
+
+  it('should warn about old mocha version', async () => {
+    expect(strykerLog).contains('DEPRECATED: Mocha < 6 detected. Please upgrade to at least Mocha version 6. Stryker will drop support for Mocha < 6 in V5');
+  });
+
+});

packages/mocha-runner/src/LibWrapper.ts

@@ -1,8 +1,12 @@
+import path = require('path');
+
 import * as Mocha from 'mocha';
 import glob = require('glob');
 
 import { MochaOptions } from '../src-generated/mocha-runner-options';
 
+const mochaRoot = path.dirname(require.resolve('mocha/package.json'));
+
 let loadOptions: undefined | ((argv?: string[] | string) => { [key: string]: any } | undefined);
 let collectFiles: undefined | ((options: MochaOptions) => string[]);
 let handleRequires: undefined | ((requires?: string[]) => Promise<any>);
@@ -14,21 +18,21 @@ try {
    * @since 6.0.0'
    * @see https://mochajs.org/api/module-lib_cli_options.html#.loadOptions
    */
-  loadOptions = require('mocha/lib/cli/options').loadOptions;
+  loadOptions = require(`${mochaRoot}/lib/cli/options`).loadOptions;
 } catch {
   // Mocha < 6 doesn't support `loadOptions`
 }
 
 try {
   // https://github.com/mochajs/mocha/blob/master/lib/cli/run-helpers.js#L132
-  const runHelpers = require('mocha/lib/cli/run-helpers');
+  const runHelpers = require(`${mochaRoot}/lib/cli/run-helpers`);
   collectFiles = runHelpers.handleFiles;
   handleRequires = runHelpers.handleRequires; // handleRequires is available since mocha v7.2
   loadRootHooks = runHelpers.loadRootHooks; // loadRootHooks is available since mocha v7.2
 
   if (!collectFiles) {
     // Might be moved: https://github.com/mochajs/mocha/commit/15b96afccaf508312445770e3af1c145d90b28c6#diff-39b692a81eb0c9f3614247af744ab4a8
-    collectFiles = require('mocha/lib/cli/collect-files');
+    collectFiles = require(`${mochaRoot}/lib/cli/collect-files`);
   }
 } catch {
   // Mocha < 6 doesn't support `handleFiles`

packages/mocha-runner/src/MochaOptionsLoader.ts

@@ -44,7 +44,7 @@ export default class MochaOptionsLoader {
       this.log.debug("Mocha >= 6 detected. Using mocha's `%s` to load mocha options", LibWrapper.loadOptions.name);
       return this.loadMocha6Options(overrides);
     } else {
-      this.log.warn('DEPRECATED: Mocha < 6 detected. Please upgrade to at least Mocha version 6.');
+      this.log.warn('DEPRECATED: Mocha < 6 detected. Please upgrade to at least Mocha version 6. Stryker will drop support for Mocha < 6 in V5.');
       this.log.debug('Mocha < 6 detected. Using custom logic to parse mocha options');
       return this.loadLegacyMochaOptsFile(overrides);
     }

packages/mocha-runner/test/unit/MochaOptionsLoader.spec.ts

@@ -130,7 +130,9 @@ describe(MochaOptionsLoader.name, () => {
     it('should log deprecated mocha version warning', async () => {
       existsFileStub.returns(false);
       sut.load(options);
-      expect(testInjector.logger.warn).calledWith('DEPRECATED: Mocha < 6 detected. Please upgrade to at least Mocha version 6.');
+      expect(testInjector.logger.warn).calledWith(
+        'DEPRECATED: Mocha < 6 detected. Please upgrade to at least Mocha version 6. Stryker will drop support for Mocha < 6 in V5.'
+      );
     });
 
     it('should load a mocha.opts file if specified', () => {