fix missing index.mjs; use better smoke tests

.travis.yml

@@ -75,9 +75,15 @@ jobs:
       stage: smoke
       env: null
       before_install: true
-      install: npm install --production
+      install: false
       name: 'Latest Node.js'
-      script: ./bin/mocha --no-config --reporter spec test/smoke/smoke.spec.js
+      script: |
+        TARBALL=$(npm pack) && \
+        mkdir -p /tmp/mocha-smoke && \
+        cp -r test/smoke /tmp/mocha-smoke && \
+        cd /tmp/mocha-smoke && \
+        npm install ~1/$TARBALL && \
+        node_modules/.bin/mocha --no-config ./smoke
       cache:
         directories:
           - ~/.npm

package.json

@@ -151,7 +151,8 @@
     "index.js",
     "mocha.css",
     "mocha.js",
-    "browser-entry.js"
+    "browser-entry.js",
+    "index.mjs"
   ],
   "browserify": {
     "transform": [

test/smoke/smoke-cjs.spec.js

@@ -0,0 +1,18 @@
+'use strict';
+
+// This test ensures Mocha's dependencies are properly in place,
+// and is intended to be run after an `npm install --production` in a clean
+// working copy. It helps avoid publishing Mocha with `dependencies`
+// in `devDependencies` or otherwise in the wrong place.
+// It does not ensure that all files are present in the published package!
+
+var assert = require('assert');
+var mocha = require('mocha');
+var describe = mocha.describe;
+var it = mocha.it;
+
+describe('a production installation of Mocha via CJS', function() {
+  it('should be able to execute a test', function() {
+    assert.ok(true);
+  });
+});

test/smoke/smoke-esm.spec.mjs

@@ -0,0 +1,14 @@
+// This test ensures Mocha's dependencies are properly in place,
+// and is intended to be run after an `npm install --production` in a clean
+// working copy. It helps avoid publishing Mocha with `dependencies`
+// in `devDependencies` or otherwise in the wrong place.
+// It does not ensure that all files are present in the published package!
+
+import assert from 'assert';
+import {describe, it} from 'mocha';
+
+describe('a production installation of Mocha via ESM', function() {
+  it('should be able to execute a test', function() {
+    assert.ok(true);
+  });
+});

test/smoke/smoke-globals.spec.js

@@ -0,0 +1,15 @@
+'use strict';
+
+// This test ensures Mocha's dependencies are properly in place,
+// and is intended to be run after an `npm install --production` in a clean
+// working copy. It helps avoid publishing Mocha with `dependencies`
+// in `devDependencies` or otherwise in the wrong place.
+// It does not ensure that all files are present in the published package!
+
+var assert = require('assert');
+
+describe('a production installation of Mocha via globals', function() {
+  it('should be able to execute a test', function() {
+    assert.ok(true);
+  });
+});