add mocha snapshot sanity test

package.json

@@ -33,7 +33,9 @@
     "binary-upload": "node ./scripts/binary.js upload",
     "binary-deploy": "node ./scripts/binary.js deploy",
     "binary-deploy-linux": "./scripts/build-linux-binary.sh",
-    "release": "gulp release"
+    "release": "gulp release",
+    "test-mocha": "mocha --reporter spec scripts/spec.js",
+    "test-mocha-snapshot": "mocha scripts/mocha-snapshot-spec.js"
   },
   "lint-staged": {
     "*.js": [
@@ -63,6 +65,7 @@
     "eslint-plugin-mocha": "^4.11.0",
     "eslint-plugin-react": "^7.3.0",
     "execa": "^0.8.0",
+    "execa-wrap": "^1.1.0",
     "filesize": "^3.5.10",
     "fs-extra": "^2.1.2",
     "gulp": "^3.9.1",
@@ -85,6 +88,7 @@
     "plist": "^2.1.0",
     "pluralize": "^6.0.0",
     "prefixed-list": "^1.0.1",
+    "snap-shot-it": "^4.0.1",
     "stop-only": "^1.1.0",
     "typescript": "^2.3.4",
     "vagrant": "0.0.1",

scripts/mocha-snapshot-spec.js

@@ -0,0 +1,17 @@
+const execa = require('execa-wrap')
+const snapshot = require('snap-shot-it')
+const { join } = require('path')
+
+function normalize (s) {
+  // assuming the test command tests this spec file
+  const scriptPath = join('scripts', 'spec.js')
+  return s.replace(process.cwd(), '<folder path>')
+    .replace(scriptPath, '<spec relative path>')
+}
+
+/* eslint-env mocha */
+it('captures mocha output', () => {
+  return execa('npm', ['run', 'test-mocha'])
+    .then(normalize)
+    .then(snapshot)
+})

scripts/spec.js

@@ -0,0 +1,4 @@
+/* eslint-env mocha */
+describe('mocha sanity check', () => {
+  it('works', () => {})
+})