diff --git a/karma-esm.conf.js b/karma-esm.conf.js
index 1287d01d68..8c85c7c3aa 100644
--- a/karma-esm.conf.js
+++ b/karma-esm.conf.js
@@ -2,10 +2,11 @@
 
 module.exports = function(config) {
   config.set({
+    basePath: "./output/karma",
     frameworks: [ 'mocha' ],
     files: [
-        { pattern: "./packages/ethers/dist/ethers-all.esm.min.js", type: "module" },
-        { pattern: "./packages/tests/dist/tests.esm.js", type: "module" }
+        { pattern: "./ethers.esm.js", type: "module" },
+        { pattern: "./tests.esm.js", type: "module" }
     ],
     reporters: [ 'karma' ],
     plugins: [
diff --git a/karma-umd.conf.js b/karma-umd.conf.js
index eb7883bb24..5231a9b9aa 100644
--- a/karma-umd.conf.js
+++ b/karma-umd.conf.js
@@ -2,10 +2,11 @@
 
 module.exports = function(config) {
   config.set({
+    basePath: "./output/karma",
     frameworks: [ 'mocha' ],
     files: [
-        "./packages/ethers/dist/ethers-all.umd.min.js",
-        "./packages/tests/dist/tests.umd.js",
+        "./ethers.umd.js",
+        "./tests.umd.js",
     ],
     reporters: [ 'karma' ],
     plugins: [
@@ -41,7 +42,7 @@ module.exports = function(config) {
     /*
     client: {
       mocha: {
-        grep: 'Etherscan',
+        grep: 'Test WebSocketProvider',
       }
     }
     */
diff --git a/misc/admin/lib/cmds/bundle-testcases.js b/misc/admin/lib/cmds/bundle-testcases.js
index 0f0bf9923d..e2455d30d9 100644
--- a/misc/admin/lib/cmds/bundle-testcases.js
+++ b/misc/admin/lib/cmds/bundle-testcases.js
@@ -25,6 +25,7 @@ const path_1 = require("path");
 const zlib_1 = __importDefault(require("zlib"));
 const log_1 = require("../log");
 const path_2 = require("../path");
+const utils_1 = require("../utils");
 const config = {
     dirs: [
         "./input/easyseed-bip39",
@@ -51,6 +52,9 @@ const config = {
                 console.log(`  - Added ${key} (${data[key].length} bytes)`);
             });
         });
+        utils_1.mkdir(path_2.resolve("packages/testcases/lib"));
+        utils_1.mkdir(path_2.resolve("packages/testcases/lib._esm"));
+        utils_1.mkdir(path_2.resolve("packages/testcases/lib.esm"));
         // We write it out to all needed places
         fs_1.default.writeFileSync(path_2.resolve("packages/testcases/lib/browser-data.json"), JSON.stringify(data));
         fs_1.default.writeFileSync(path_2.resolve("packages/testcases/lib._esm/browser-data.json"), JSON.stringify(data));
diff --git a/misc/admin/lib/cmds/setup-karma-tests.d.ts b/misc/admin/lib/cmds/setup-karma-tests.d.ts
new file mode 100644
index 0000000000..cb0ff5c3b5
--- /dev/null
+++ b/misc/admin/lib/cmds/setup-karma-tests.d.ts
@@ -0,0 +1 @@
+export {};
diff --git a/misc/admin/lib/cmds/setup-karma-tests.js b/misc/admin/lib/cmds/setup-karma-tests.js
new file mode 100644
index 0000000000..96180c9ffa
--- /dev/null
+++ b/misc/admin/lib/cmds/setup-karma-tests.js
@@ -0,0 +1,37 @@
+"use strict";
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
+var __importDefault = (this && this.__importDefault) || function (mod) {
+    return (mod && mod.__esModule) ? mod : { "default": mod };
+};
+Object.defineProperty(exports, "__esModule", { value: true });
+const fs_1 = __importDefault(require("fs"));
+const path_1 = require("../path");
+const utils_1 = require("../utils");
+function copy(src, dst, transform) {
+    let data = fs_1.default.readFileSync(path_1.resolve(src));
+    if (transform) {
+        data = Buffer.from(transform(data.toString()));
+    }
+    fs_1.default.writeFileSync(dst, data);
+}
+(function () {
+    return __awaiter(this, void 0, void 0, function* () {
+        yield utils_1.mkdir(path_1.resolve("output/karma"));
+        copy(path_1.resolve("packages/ethers/dist/ethers.esm.js"), path_1.resolve("output/karma/ethers.esm.js"));
+        copy(path_1.resolve("packages/tests/dist/tests.esm.js"), path_1.resolve("output/karma/tests.esm.js"), (data) => {
+            return data.replace(/^(import [^;]* from ')(ethers)(';)/, (all, prefix, id, suffix) => {
+                return prefix + "./ethers.esm.js" + suffix;
+            });
+        });
+        copy(path_1.resolve("packages/ethers/dist/ethers.umd.js"), path_1.resolve("output/karma/ethers.umd.js"));
+        copy(path_1.resolve("packages/tests/dist/tests.umd.js"), path_1.resolve("output/karma/tests.umd.js"));
+    });
+})();
diff --git a/misc/admin/src.ts/cmds/bundle-testcases.ts b/misc/admin/src.ts/cmds/bundle-testcases.ts
index f48bef0962..4930f5d33c 100644
--- a/misc/admin/src.ts/cmds/bundle-testcases.ts
+++ b/misc/admin/src.ts/cmds/bundle-testcases.ts
@@ -16,6 +16,7 @@ import zlib from "zlib";
 
 import { colorify } from "../log";
 import { resolve } from "../path";
+import { mkdir } from "../utils";
 
 const config = {
     dirs: [
@@ -45,6 +46,10 @@ const config = {
         });
     });
 
+    mkdir(resolve("packages/testcases/lib"));
+    mkdir(resolve("packages/testcases/lib._esm"));
+    mkdir(resolve("packages/testcases/lib.esm"));
+
     // We write it out to all needed places
     fs.writeFileSync(resolve("packages/testcases/lib/browser-data.json"), JSON.stringify(data));
     fs.writeFileSync(resolve("packages/testcases/lib._esm/browser-data.json"), JSON.stringify(data));
diff --git a/misc/admin/src.ts/cmds/setup-karma-tests.ts b/misc/admin/src.ts/cmds/setup-karma-tests.ts
new file mode 100644
index 0000000000..6bca882e47
--- /dev/null
+++ b/misc/admin/src.ts/cmds/setup-karma-tests.ts
@@ -0,0 +1,27 @@
+
+import fs from "fs";
+
+import { resolve } from "../path";
+import { mkdir } from "../utils";
+
+function copy(src: string, dst: string, transform?: (data: string) => string): void {
+    let data = fs.readFileSync(resolve(src));
+    if (transform) {
+        data = Buffer.from(transform(data.toString()));
+    }
+    fs.writeFileSync(dst, data);
+}
+
+(async function() {
+    await mkdir(resolve("output/karma"));
+
+    copy(resolve("packages/ethers/dist/ethers.esm.js"), resolve("output/karma/ethers.esm.js"));
+    copy(resolve("packages/tests/dist/tests.esm.js"), resolve("output/karma/tests.esm.js"), (data) => {
+        return data.replace(/^(import [^;]* from ')(ethers)(';)/, (all, prefix, id, suffix) => {
+            return prefix + "./ethers.esm.js" + suffix;
+        });
+    });
+
+    copy(resolve("packages/ethers/dist/ethers.umd.js"), resolve("output/karma/ethers.umd.js"));
+    copy(resolve("packages/tests/dist/tests.umd.js"), resolve("output/karma/tests.umd.js"));
+})();
diff --git a/package.json b/package.json
index 0e345be43a..262a9882f9 100644
--- a/package.json
+++ b/package.json
@@ -16,14 +16,14 @@
     "_build-cjs": "node ./misc/admin/lib/cmds/echo 'Building CommonJS libraries...' && node ./misc/admin/lib/cmds/set-build-option cjs && npm run build",
     "_build-esm": "node ./misc/admin/lib/cmds/echo 'Building ES modules libraries...' && node ./misc/admin/lib/cmds/set-build-option esm && npm run build",
     "clean": "node ./misc/admin/lib/cmds/echo 'Cleaning all build files...' && rm -rf packages/*/lib packages/*/lib._esm packages/*/lib.esm packages/*/node_modules packages/*/dist/*.js packages/*/tsconfig.tsbuildinfo node_modules .package_node_modules package-lock.json",
-    "_test-dist": "node ./misc/admin/lib/cmds/bundle-testcases && rollup -c rollup-tests.config.js",
+    "_test-dist": "rollup -c rollup-tests.config.js && node ./misc/admin/lib/cmds/setup-karma-tests",
     "_test-browser-umd": "karma start --single-run --browsers HeadlessLittleLiar karma-umd.conf.js",
     "_test-browser-esm": "karma start --single-run --browsers HeadlessLittleLiar karma-esm.conf.js",
     "test-browser-umd": "npm run _test-dist && npm run _test-browser-umd",
     "test-browser-esm": "npm run _test-dist && npm run _test-browser-esm",
     "test-coverage": "nyc --report-dir=output --reporter=lcov --reporter=text mocha --reporter ./packages/tests/reporter-keepalive ./packages/tests/lib/test-*.js | tee output/summary.txt",
     "test-node": "mocha --no-colors --reporter ./packages/tests/reporter ./packages/tests/lib/test-*.js",
-    "test-react": "npm run _test-dist && npm run build-dist-shims && pushd misc/ReactNativeTestApp && ./run-tests.sh && popd",
+    "test-react": "npm run _test-dist && pushd misc/ReactNativeTestApp && ./run-tests.sh && popd",
     "test": "npm run build-all && npm run test-node",
     "build-docs": "flatworm docs.wrm docs",
     "serve-docs": "node ./misc/admin/lib/cmds/serve-docs.js",
@@ -31,7 +31,7 @@
     "spell-check": "node ./misc/admin/lib/cmds/spell-check.js",
     "_reset-build": "node ./misc/admin/lib/cmds/set-build-option cjs",
     "_esm-alias": "node ./misc/admin/lib/cmds/echo 'Bundling ESM elliptic (lib._esm/browser-elliptic.js)...' && rollup -c rollup-pre-alias.config.js && node misc/admin/lib/cmds/esm-alias",
-    "build-libs": "node ./misc/admin/lib/cmds/update-exports.js && node ./misc/admin/lib/cmds/bundle-testcases && npm run _build-cjs && npm run _build-esm && npm _reset-build && node packages/asm/generate.js && npm run _esm-alias && chmod 755 packages/*/lib/bin/*.js",
+    "build-libs": "node ./misc/admin/lib/cmds/update-exports.js && node ./misc/admin/lib/cmds/bundle-testcases && npm run _build-cjs && npm run _build-esm && npm run _reset-build && node packages/asm/generate.js && npm run _esm-alias && chmod 755 packages/*/lib/bin/*.js",
     "build-dist-shims": "rollup -c rollup-shims.config.js && uglifyjs --compress --mangle --output ./packages/shims/dist/index.min.js -- ./packages/shims/dist/index.js",
     "build-dist-libs": "rollup -c rollup-dist.config.js && uglifyjs packages/ethers/dist/ethers.umd.js --output packages/ethers/dist/ethers.umd.min.js --source-map 'content=packages/ethers/dist/ethers.umd.js.map' && uglifyjs packages/ethers/dist/ethers.esm.js --output packages/ethers/dist/ethers.esm.min.js --source-map 'content=packages/ethers/dist/ethers.esm.js.map'",
     "_build-dist": "node ./misc/admin/lib/cmds/echo 'Building dist files...' && npm run build-dist-libs && npm run build-dist-shims",
@@ -54,22 +54,20 @@
     "aws-sdk": "2.137.0",
     "diff": "4.0.1",
     "flatworm": "0.0.2-beta.5",
-    "jison": "^0.4.18",
-    "karma": "5.1.0",
+    "jison": "0.4.18",
+    "karma": "5.2.3",
     "karma-chrome-launcher": "3.1.0",
     "karma-mocha": "2.0.1",
     "libnpmpublish": "3.0.1",
     "mocha": "^7.1.1",
     "nyc": "15.1.0",
-    "rollup": "1.20.1",
+    "rollup": "2.33.2",
     "rollup-plugin-node-polyfills": "0.2.1",
     "rollup-plugin-sourcemaps": "0.6.3",
     "scrypt-js": "3.0.1",
     "semver": "^5.6.0",
     "typescript": "3.8.3",
-    "uglify-es": "3.3.9",
-    "webpack": "^4.44.2",
-    "webpack-cli": "4.1.0"
+    "uglify-es": "3.3.9"
   },
   "dependencies": {
     "@babel/parser": "7.8.4",
@@ -81,7 +79,6 @@
     "aes-js": "3.0.0",
     "bech32": "1.1.4",
     "bn.js": "^4.4.0",
-    "browserify-zlib": "^0.2.0",
     "elliptic": "6.5.3",
     "hash.js": "1.1.3",
     "js-sha3": "0.5.7",
diff --git a/packages/ethers/src.ts/index.ts b/packages/ethers/src.ts/index.ts
index caa266aac7..dbcdf4b8f1 100644
--- a/packages/ethers/src.ts/index.ts
+++ b/packages/ethers/src.ts/index.ts
@@ -4,14 +4,6 @@
 
 import * as ethers from "./ethers";
 
-try {
-    const anyGlobal = (window as any);
-
-    if (anyGlobal._ethers == null) {
-        anyGlobal._ethers = ethers;
-    }
-} catch (error) { }
-
 export { ethers };
 
 export {
diff --git a/packages/hardware-wallets/src.ts/browser-ethers.ts b/packages/hardware-wallets/src.ts/browser-ethers.ts
deleted file mode 100644
index a755756a09..0000000000
--- a/packages/hardware-wallets/src.ts/browser-ethers.ts
+++ /dev/null
@@ -1,12 +0,0 @@
-"use strict";
-
-let ethers: any = { };
-
-const w = (window as any);
-if (w._ethers == null) {
-    console.log("WARNING: @ethersproject/hardware-wallet requires ethers loaded first");
-} else {
-    ethers = w._ethers;
-}
-
-export { ethers }
diff --git a/packages/tests/src.ts/browser-ethers.ts b/packages/tests/src.ts/browser-ethers.ts
deleted file mode 100644
index 7d3ea2d588..0000000000
--- a/packages/tests/src.ts/browser-ethers.ts
+++ /dev/null
@@ -1,9 +0,0 @@
-'use strict';
-
-console.log("Using global.ethers");
-
-const anyGlobal = (window as any);
-
-const ethers = anyGlobal._ethers;
-
-export { ethers }
diff --git a/rollup-dist.config.js b/rollup-dist.config.js
index 399625a3ff..73b8349df7 100644
--- a/rollup-dist.config.js
+++ b/rollup-dist.config.js
@@ -149,7 +149,7 @@ function getConfig() {
 }
 */
 const configs = [
-//    getEsmConfig(),
+    getEsmConfig(),
     getUmdConfig()
 ];
 
diff --git a/rollup-tests.config.js b/rollup-tests.config.js
index 8305ec73cf..40d9cbf995 100644
--- a/rollup-tests.config.js
+++ b/rollup-tests.config.js
@@ -8,7 +8,19 @@ import nodePolyfills from "rollup-plugin-node-polyfills";
 
 import json from "@rollup/plugin-json";
 
-function getConfig(format, input, mainFields) {
+function getConfig(format) {
+
+    // ESM config
+    let input = "./packages/tests/lib.esm/index.js";
+    let mainFields = undefined;
+    let globals = undefined;
+
+    if (format === "umd") {
+        input = "./packages/tests/lib/index.js";
+        mainFields = [ "browser", "main" ];
+        globals = { ethers: "ethers"  };
+    }
+
     const plugins = [
         json(),
         /*
@@ -34,19 +46,20 @@ function getConfig(format, input, mainFields) {
       input: input,
       output: {
         file: ("./packages/tests/dist/tests." + format + ".js"),
-        format: format,
-        name: "testing"
+        name: "testing",
+        format,
+        globals
       },
       context: "window",
       treeshake: false,
+      external: [ "ethers" ],
       plugins: plugins
   };
 }
 
 const configs = [
-    getConfig("umd", "./packages/tests/lib/index.js", [ "_browser-all", "browser", "main" ]),
-    getConfig("esm", "./packages/tests/lib.esm/index.js", undefined),
+    getConfig("umd"),
+    getConfig("esm"),
 ];
 
 export default configs;
-