add wrapper around process.cwd()

- better isolation
- a use of `process.cwd()` in `lib/runner.js` was left in place to avoid conflicts, because another PR will remove it

lib/cli/cli.js

@@ -19,6 +19,7 @@ const {loadOptions, YARGS_PARSER_CONFIG} = require('./options');
 const commands = require('./commands');
 const ansi = require('ansi-colors');
 const {repository, homepage, version, gitter} = require('../../package.json');
+const {cwd} = require('../utils');
 
 /**
  * - Accepts an `Array` of arguments
@@ -31,7 +32,7 @@ exports.main = (argv = process.argv.slice(2)) => {
   debug('entered main with raw args', argv);
   // ensure we can require() from current working directory
   if (typeof module.paths !== 'undefined') {
-    module.paths.push(process.cwd(), path.resolve('node_modules'));
+    module.paths.push(cwd(), path.resolve('node_modules'));
   }
 
   Error.stackTraceLimit = Infinity; // configurable via --stack-trace-limit?

lib/cli/config.js

@@ -11,6 +11,7 @@ const fs = require('fs');
 const path = require('path');
 const debug = require('debug')('mocha:cli:config');
 const findUp = require('find-up');
+const utils = require('../utils');
 
 /**
  * These are the valid config files, in order of precedence;
@@ -92,7 +93,7 @@ exports.loadConfig = filepath => {
  * @param {string} [cwd] - Current working directory
  * @returns {string|null} Filepath to config, if found
  */
-exports.findConfig = (cwd = process.cwd()) => {
+exports.findConfig = (cwd = utils.cwd()) => {
   const filepath = findUp.sync(exports.CONFIG_FILES, {cwd});
   if (filepath) {
     debug('findConfig: found config file %s', filepath);

lib/mocha.js

@@ -58,7 +58,7 @@ var mochaStates = utils.defineConstants({
  */
 
 if (!process.browser && typeof module.paths !== 'undefined') {
-  var cwd = process.cwd();
+  var cwd = utils.cwd();
   module.paths.push(cwd, path.join(cwd, 'node_modules'));
 }
 
@@ -236,7 +236,7 @@ Mocha.prototype.reporter = function(reporter, reporterOptions) {
         ) {
           // Try to load reporters from a path (absolute or relative)
           try {
-            _reporter = require(path.resolve(reporter));
+            _reporter = require(path.resolve(utils.cwd(), reporter));
           } catch (_err) {
             _err.code === 'MODULE_NOT_FOUND' ||
             _err.message.indexOf('Cannot find module') >= 0

lib/utils.js

@@ -637,7 +637,7 @@ exports.stackTraceFilter = function() {
   var slash = path.sep;
   var cwd;
   if (is.node) {
-    cwd = process.cwd() + slash;
+    cwd = exports.cwd() + slash;
   } else {
     cwd = (typeof location === 'undefined'
       ? window.location
@@ -821,3 +821,13 @@ exports.supportsEsModules = function() {
     }
   }
 };
+
+/**
+ * Returns current working directory
+ *
+ * Wrapper around `process.cwd()` for isolation
+ * @private
+ */
+exports.cwd = function cwd() {
+  return process.cwd();
+};

test/node-unit/mocha.spec.js

@@ -26,7 +26,8 @@ describe('Mocha', function() {
       supportsEsModules: sandbox.stub().returns(false),
       warn: sandbox.stub(),
       isString: sandbox.stub(),
-      noop: sandbox.stub()
+      noop: sandbox.stub(),
+      cwd: sandbox.stub().returns(process.cwd())
     };
     stubs.suite = Object.assign(sandbox.createStubInstance(EventEmitter), {
       slow: sandbox.stub(),
@@ -106,10 +107,9 @@ describe('Mocha', function() {
     describe('reporter()', function() {
       describe('when a reporter exists relative to the cwd', function() {
         beforeEach(function() {
-          // DANGER!
-          sandbox
-            .stub(process, 'cwd')
-            .returns(path.resolve(__dirname, '..', '..', 'lib', 'reporters'));
+          stubs.utils.cwd.returns(
+            path.resolve(__dirname, '..', '..', 'lib', 'reporters')
+          );
         });
 
         it('should load from current working directory', function() {

test/node-unit/utils.spec.js

@@ -0,0 +1,20 @@
+'use strict';
+
+const rewiremock = require('rewiremock/node');
+
+describe('utils', function() {
+  let utils;
+
+  beforeEach(function() {
+    // add deps to be mocked as needed to second parameter
+    utils = rewiremock.proxy('../../lib/utils', {});
+  });
+
+  describe('function', function() {
+    describe('cwd()', function() {
+      it('should return the current working directory', function() {
+        expect(utils.cwd(), 'to be', process.cwd());
+      });
+    });
+  });
+});