chore: switch Runnable, Hook, and Test from util.inherits to ES2015 classes (#5178)

Co-authored-by: Mark Wiemer <markwiemer@outlook.com>

Author: JoshuaKGoldberg

lib/hook.js

@@ -1,89 +1,81 @@
 "use strict";
 
 var Runnable = require("./runnable");
-const { inherits, constants } = require("./utils");
+const { constants } = require("./utils");
 const { MOCHA_ID_PROP_NAME } = constants;
 
-/**
- * Expose `Hook`.
- */
-
-module.exports = Hook;
-
-/**
- * Initialize a new `Hook` with the given `title` and callback `fn`
- *
- * @class
- * @extends Runnable
- * @param {String} title
- * @param {Function} fn
- */
-function Hook(title, fn) {
-  Runnable.call(this, title, fn);
-  this.type = "hook";
-}
+class Hook extends Runnable {
+  /**
+   * Initialize a new `Hook` with the given `title` and callback `fn`
+   *
+   * @extends Runnable
+   * @param {String} title
+   * @param {Function} fn
+   */
+  constructor(title, fn) {
+    super(title, fn);
+    this.type = "hook";
+  }
 
-/**
- * Inherit from `Runnable.prototype`.
- */
-inherits(Hook, Runnable);
+  /**
+   * Resets the state for a next run.
+   */
+  reset() {
+    super.reset(this);
+    delete this._error;
+  }
 
-/**
- * Resets the state for a next run.
- */
-Hook.prototype.reset = function () {
-  Runnable.prototype.reset.call(this);
-  delete this._error;
-};
+  /**
+   * Get or set the test `err`.
+   *
+   * @memberof Hook
+   * @public
+   * @param {Error} err
+   * @return {Error}
+   */
+  error(err) {
+    if (!arguments.length) {
+      err = this._error;
+      this._error = null;
+      return err;
+    }
 
-/**
- * Get or set the test `err`.
- *
- * @memberof Hook
- * @public
- * @param {Error} err
- * @return {Error}
- */
-Hook.prototype.error = function (err) {
-  if (!arguments.length) {
-    err = this._error;
-    this._error = null;
-    return err;
+    this._error = err;
   }
 
-  this._error = err;
-};
+  /**
+   * Returns an object suitable for IPC.
+   * Functions are represented by keys beginning with `$$`.
+   * @private
+   * @returns {Object}
+   */
+  serialize() {
+    return {
+      $$currentRetry: this.currentRetry(),
+      $$fullTitle: this.fullTitle(),
+      $$isPending: Boolean(this.isPending()),
+      $$titlePath: this.titlePath(),
+      ctx:
+        this.ctx && this.ctx.currentTest
+          ? {
+              currentTest: {
+                title: this.ctx.currentTest.title,
+                [MOCHA_ID_PROP_NAME]: this.ctx.currentTest.id,
+              },
+            }
+          : {},
+      duration: this.duration,
+      file: this.file,
+      parent: {
+        $$fullTitle: this.parent.fullTitle(),
+        [MOCHA_ID_PROP_NAME]: this.parent.id,
+      },
+      state: this.state,
+      title: this.title,
+      type: this.type,
+      [MOCHA_ID_PROP_NAME]: this.id,
+    };
+  }
+}
 
-/**
- * Returns an object suitable for IPC.
- * Functions are represented by keys beginning with `$$`.
- * @private
- * @returns {Object}
- */
-Hook.prototype.serialize = function serialize() {
-  return {
-    $$currentRetry: this.currentRetry(),
-    $$fullTitle: this.fullTitle(),
-    $$isPending: Boolean(this.isPending()),
-    $$titlePath: this.titlePath(),
-    ctx:
-      this.ctx && this.ctx.currentTest
-        ? {
-            currentTest: {
-              title: this.ctx.currentTest.title,
-              [MOCHA_ID_PROP_NAME]: this.ctx.currentTest.id,
-            },
-          }
-        : {},
-    duration: this.duration,
-    file: this.file,
-    parent: {
-      $$fullTitle: this.parent.fullTitle(),
-      [MOCHA_ID_PROP_NAME]: this.parent.id,
-    },
-    state: this.state,
-    title: this.title,
-    type: this.type,
-    [MOCHA_ID_PROP_NAME]: this.id,
-  };
-};
+module.exports = Hook;