Introduce dist/qunit-dom-modules.js

Begins splitting things apart to be more compatible with not assuming
QUnit is am ambient global.

lib/install.ts

@@ -0,0 +1,35 @@
+import DOMAssertions from './assertions';
+
+declare global {
+  interface Assert {
+    dom(target?: string | Element | null, rootElement?: Element): DOMAssertions;
+  }
+}
+
+export default function (QUnit: QUnit) {
+  QUnit.assert.dom = function (
+    target?: string | Element | null,
+    rootElement?: Element
+  ): DOMAssertions {
+    if (!isValidRootElement(rootElement)) {
+      throw new Error(`${rootElement} is not a valid root element`);
+    }
+
+    rootElement = rootElement || this.dom.rootElement || document;
+
+    if (arguments.length === 0) {
+      target = rootElement;
+    }
+
+    return new DOMAssertions(target, rootElement, this);
+  };
+
+  function isValidRootElement(element: any): element is Element {
+    return (
+      !element ||
+      (typeof element === 'object' &&
+        typeof element.querySelector === 'function' &&
+        typeof element.querySelectorAll === 'function')
+    );
+  }
+}

lib/qunit-dom-globals.ts

@@ -0,0 +1,5 @@
+/* global QUnit */
+
+import install from './install';
+
+install(QUnit);

lib/qunit-dom-modules.ts

@@ -0,0 +1,4 @@
+import * as QUnit from 'qunit';
+import install from './install';
+
+install(QUnit);

rollup.config.js

@@ -1,23 +1,38 @@
 import typescript from 'rollup-plugin-typescript2';
 
-export default {
-  input: 'lib/qunit-dom.ts',
+const typescriptConfiguration = {
+  exclude: [
+    'node_modules/**',
+    'lib/**/__tests__/**',
+    'lib/**/*.test.ts',
+    'lib/helpers/test-assertions.ts',
+  ],
+};
+
+const iifeBundle = {
+  input: 'lib/qunit-dom-globals.ts',
 
   external: ['qunit'],
-  plugins: [
-    typescript({
-      exclude: [
-        'node_modules/**',
-        'lib/**/__tests__/**',
-        'lib/**/*.test.ts',
-        'lib/helpers/test-assertions.ts',
-      ],
-    }),
-  ],
+  plugins: [typescript(typescriptConfiguration)],
 
   output: {
     file: 'dist/qunit-dom.js',
     format: 'iife',
     sourcemap: true,
   },
 };
+
+const esBundle = {
+  input: 'lib/qunit-dom-modules.ts',
+
+  external: ['qunit'],
+  plugins: [typescript(typescriptConfiguration)],
+
+  output: {
+    file: 'dist/qunit-dom.es.js',
+    format: 'es',
+    sourcemap: true,
+  },
+};
+
+export default [iifeBundle, esBundle];