Update 'esm' dependency (sinonjs#2053)

Requires a small fix to the setup, as 'esm' would complain with
Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: /Users/fatso/dev/sinon/test/es2015/module-support-assessment-test.mjs
when encountering '*.mjs' files

package.json

@@ -20,7 +20,7 @@
  "test-coverage": "nyc npm run test-headless -- --transform [ babelify --ignore [ test ] --plugins [ babel-plugin-istanbul ] ]",
  "test-cloud": "npm run test-headless -- --wd",
  "test-webworker": "mochify --https-server 8080 test/webworker/webworker-support-assessment.js",
- "test-esm": "mocha -r esm test/es2015/module-support-assessment-test.mjs",
+ "test-esm": "mocha -r esm test/es2015/module-support-assessment-test.es6",
  "test-esm-bundle": "node test/es2015/check-esm-bundle-is-runnable.js",
  "test-docker-image": "docker-compose up",
  "test": "run-s test-node test-headless test-webworker test-esm",
@@ -78,7 +78,7 @@
  "eslint-plugin-local-rules": "^0.1.0",
  "eslint-plugin-mocha": "^5.3.0",
  "eslint-plugin-prettier": "^3.0.1",
- "esm": "3.0.37",
+ "esm": "^3.2.25",
  "husky": "^0.14.2",
  "lint-staged": "^6.0.0",
  "markdownlint-cli": "^0.8.2",
@@ -112,5 +112,12 @@
  "main": "./lib/sinon.js",
  "module": "./pkg/sinon-esm.js",
  "cdn": "./pkg/sinon.js",
- "jsdelivr": "./pkg/sinon.js"
+ "jsdelivr": "./pkg/sinon.js",
+ "esm": {
+ "cjs": {
+ "mutableNamespace": false,
+ "cache":true
+ },
+ "mode": "auto"
+ }
 }

test/es2015/module-support-assessment-test.mjs → test/es2015/module-support-assessment-test.es6

@@ -1,12 +1,21 @@
-import referee from "@sinonjs/referee";
-import sinon from "../../lib/sinon";
+/**
+ * About these tests:
+ * These tests concern EcmaScript Modules. That is, they test Sinon's behaviour
+ * when running in a EcmaScript 2015+ environment that has the Module type.
+ * They do not assert how code that has been transpiled into ES5 using Babel
+ * and similar will behave.
+ */
 import * as aModule from "./a-module";
-import aModuleWithToStringTag from "./a-module-with-to-string-tag";
-import aModuleWithDefaultExport from "./a-module-with-default";
 
 // Usually one would import the default module, but one can make a form of wrapper like this
 /* eslint-disable no-unused-vars */
 import functionModule, * as functionModuleAlternative from "./a-function-module";
+
+import aModuleWithDefaultExport from "./a-module-with-default";
+import aModuleWithToStringTag from "./a-module-with-to-string-tag";
+import referee from "@sinonjs/referee";
+import sinon from "../../lib/sinon";
+
 const { assert, refute } = referee;
 
 function createTestSuite(action) {
@@ -52,7 +61,7 @@ function createTestSuite(action) {
  describe("Modules that exports a function as their default export", function() {
  it("should not be possible to spy/stub the default export using a wrapper for the exports", function() {
  assert.exception(function() {
- stub = sinon[action](functionModuleAlternative, "anExport");
+ stub = sinon[action](functionModuleAlternative, "default");
  }, errorRegEx);
  });
  });