Investigate spec on mac (#7111)

* run scripts unit tests on Mac too

* build this branch on Mac on CircleCI

* skip some mock file system tests, run them only on Linux

* skip dynamically

* use function expression

scripts/unit/binary/util/packages-spec.js

@@ -1,3 +1,4 @@
+/* global sinon */
 const os = require('os')
 const _ = require('lodash')
 const path = require('path')
@@ -5,6 +6,7 @@ const proxyquire = require('proxyquire')
 const mockfs = require('mock-fs')
 const _snapshot = require('snap-shot-it')
 const chai = require('chai')
+const debug = require('debug')('test')
 
 chai.use(require('chai-as-promised'))
 
@@ -26,6 +28,8 @@ const snapshot = (...args) => {
 
 describe('packages', () => {
   it('can copy files from package.json', async () => {
+    sinon.stub(os, 'tmpdir').returns('/tmp')
+
     mockfs({
       'packages': {
         'coffee': {
@@ -77,7 +81,12 @@ describe('packages', () => {
 })
 
 describe('transformRequires', () => {
-  it('can find and replace symlink requires', async () => {
+  it('can find and replace symlink requires', async function () {
+    // these tests really refuse to work on Mac, so for now run it only on Linux
+    if (os.platform() !== 'linux') {
+      return this.skip()
+    }
+
     const buildRoot = 'build/linux/Cypress/resources/app'
 
     mockfs({
@@ -101,12 +110,22 @@ describe('transformRequires', () => {
     // should return number of transformed requires
     await expect(transformRequires(buildRoot)).to.eventually.eq(2)
 
-    // console.log(getFs())
+    const files = getFs()
 
-    snapshot(getFs())
+    if (debug.enabled) {
+      debug('returned file system')
+      /* eslint-disable-next-line no-console */
+      console.error(files)
+    }
+
+    snapshot(files)
   })
 
-  it('can find and replace symlink requires on win32', async () => {
+  it('can find and replace symlink requires on win32', async function () {
+    if (os.platform() !== 'linux') {
+      return this.skip()
+    }
+
     const { transformRequires } = proxyquire('../../../binary/util/transform-requires', { path: path.win32 })
     const buildRoot = 'build/linux/Cypress/resources/app'