Add test case for overriding exported global name without specifying the moduleId or moduleIds options

packages/babel-plugin-transform-es2015-modules-umd/test/fixtures/umd/override-export-name/actual.js

@@ -0,0 +1 @@
+export default 42;

packages/babel-plugin-transform-es2015-modules-umd/test/fixtures/umd/override-export-name/expected.js

@@ -0,0 +1,20 @@
+(function (global, factory) {
+  if (typeof define === "function" && define.amd) {
+    define(["exports"], factory);
+  } else if (typeof exports !== "undefined") {
+    factory(exports);
+  } else {
+    var mod = {
+      exports: {}
+    };
+    factory(mod.exports);
+    global.baz = mod.exports;
+  }
+})(this, function (exports) {
+  "use strict";
+
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
+  exports.default = 42;
+});

packages/babel-plugin-transform-es2015-modules-umd/test/fixtures/umd/override-export-name/options.json

@@ -0,0 +1,11 @@
+{
+  "plugins": [
+    "external-helpers",
+    ["transform-es2015-modules-umd", {
+      "globals": {
+        "actual": "baz"
+      },
+      "exactGlobals": true
+    }]
+  ]
+}