diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 92b3ef3..1fef16d 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -1,6 +1,12 @@
 name: CI
 
-on: [push, pull_request]
+on:
+  pull_request:
+    branches:
+      - '**'
+  push:
+    branches:
+      - master
 
 jobs:
   build:
diff --git a/e2e-test/webpack-custom/babel.config.js b/e2e-test/webpack-custom/babel.config.js
new file mode 100644
index 0000000..0d4806e
--- /dev/null
+++ b/e2e-test/webpack-custom/babel.config.js
@@ -0,0 +1,9 @@
+module.exports = (api) => {
+	api.cache(true);
+
+	return {
+		plugins: [
+			['@babel/plugin-transform-react-jsx', { pragma: 'createElement' }],
+		],
+	};
+};
diff --git a/e2e-test/webpack-custom/package.json b/e2e-test/webpack-custom/package.json
index b181fa6..4116f8c 100644
--- a/e2e-test/webpack-custom/package.json
+++ b/e2e-test/webpack-custom/package.json
@@ -4,6 +4,7 @@
 	"private": true,
 	"dependencies": {
 		"@babel/core": "^7.10.3",
+		"@babel/plugin-transform-react-jsx": "^7.10.3",
 		"babel-loader": "8.1.0",
 		"babel-plugin-transform-rename-properties": "^0.1.0",
 		"karmatic": "file:../..",
diff --git a/e2e-test/webpack-custom/src/index.js b/e2e-test/webpack-custom/src/index.js
index 0dc0ae1..2e191f2 100644
--- a/e2e-test/webpack-custom/src/index.js
+++ b/e2e-test/webpack-custom/src/index.js
@@ -1,3 +1,8 @@
-export function box(value) {
-	return { _value: value };
+// eslint-disable-next-line no-unused-vars
+function createElement(tag, props) {
+	return { tag, props };
+}
+
+export function render(value1, value2) {
+	return <div _value1={value1} _value2={value2} />;
 }
diff --git a/e2e-test/webpack-custom/test/index.test.js b/e2e-test/webpack-custom/test/index.test.js
index e55386a..025e0b6 100644
--- a/e2e-test/webpack-custom/test/index.test.js
+++ b/e2e-test/webpack-custom/test/index.test.js
@@ -1,9 +1,19 @@
-import { box } from '../src/index';
+import { render } from '../src/index';
 
-describe('Box', () => {
-	it('should have a __v property', () => {
-		const boxed = box(1);
-		expect('_value' in boxed).toBe(false);
-		expect(boxed.__v).toBe(1);
+describe('Render result', () => {
+	it('should have a _value1 property', () => {
+		const result = render(1, 2);
+		expect('_value1' in result.props).toBe(true);
+		expect(result.props._value1).toBe(1);
+	});
+	it('should have a __v2 property', () => {
+		const result = render(1, 2);
+		expect('_value2' in result.props).toBe(false);
+		expect(result.props.__v2).toBe(2);
+	});
+	it('should have a __t property', () => {
+		const result = render(1, 2);
+		expect('tag' in result).toBe(false);
+		expect(result.__t).toBe('div');
 	});
 });
diff --git a/e2e-test/webpack-custom/webpack.config.js b/e2e-test/webpack-custom/webpack.config.js
index af1fa3a..bfc93f2 100644
--- a/e2e-test/webpack-custom/webpack.config.js
+++ b/e2e-test/webpack-custom/webpack.config.js
@@ -9,7 +9,7 @@ module.exports = {
 					plugins: [
 						[
 							'babel-plugin-transform-rename-properties',
-							{ rename: { _value: '__v' } },
+							{ rename: { _value2: '__v2', tag: '__t' } },
 						],
 					],
 				},
diff --git a/scripts/run-e2e-tests.mjs b/scripts/run-e2e-tests.mjs
index 7bc6456..e35a960 100644
--- a/scripts/run-e2e-tests.mjs
+++ b/scripts/run-e2e-tests.mjs
@@ -181,17 +181,22 @@ async function npmInstall(cwd, prefix) {
  */
 async function setupTests(projectPath, prefix) {
 	const name = path.basename(projectPath);
-	const log = (...msgs) => console.log(`${info(prefix)}`, ...msgs);
+	const log = (...msgs) => console.log(info(prefix), ...msgs);
+	const throwError = (...msgs) => {
+		process.exitCode = 1;
+		console.error(error(prefix), ...msgs.map((msg) => error(msg)));
+		throw new Error(msgs[0]);
+	};
 
 	log(`Beginning E2E test at`, projectPath);
 	const pkgJsonPath = path.join(projectPath, 'package.json');
 	if (!(await fileExists(pkgJsonPath))) {
 		prefix = error(prefix);
-		console.error(
-			`${prefix} Could not locate package.json for "${name}". Ensure every e2e test has a package.json defined.`
+		throwError(
+			`Could not locate package.json for "${name}".`,
+			`Ensure every e2e test has a package.json.\n`,
+			`${prefix} Expected to find one at "${pkgJsonPath}".`
 		);
-		console.error(`${prefix} Expected to find one at "${pkgJsonPath}".`);
-		throw new Error(`Could not locate package.json for "${name}".`);
 	}
 
 	const pkg = JSON.parse(await fs.readFile(pkgJsonPath, 'utf8'));
@@ -228,10 +233,22 @@ async function setupTests(projectPath, prefix) {
 			await onExit(cp);
 		} catch (e) {
 			process.exitCode = 1;
-			console.error(error(prefix) + ` Test run failed: ${e.message}`);
+			throwError(`Test run failed: ${e.message}`);
 		}
 
-		// TODO: validate coverage/lcov.info is not empty
+		const coveragePath = path.join(projectPath, 'coverage', 'lcov.info');
+		if (!(await fileExists)) {
+			throwError(
+				`Code coverage failed to generate results: Results file does not exist at ${coveragePath}`
+			);
+		}
+
+		const coverageInfo = await fs.readFile(coveragePath, { encoding: 'utf8' });
+		if (!coverageInfo) {
+			throwError(
+				`Code coverage failed to generate results: Results file is empty`
+			);
+		}
 	};
 }
 
diff --git a/src/lib/babel-loader.js b/src/lib/babel-loader.js
index 028d696..e406413 100644
--- a/src/lib/babel-loader.js
+++ b/src/lib/babel-loader.js
@@ -1,4 +1,4 @@
-export default function babelLoader(options) {
+export function getDefaultBabelLoader(options) {
 	return {
 		test: /\.jsx?$/,
 		exclude: /node_modules/,
diff --git a/src/webpack.js b/src/webpack.js
index dc887fb..df9de68 100644
--- a/src/webpack.js
+++ b/src/webpack.js
@@ -1,7 +1,7 @@
 import path from 'path';
 import delve from 'dlv';
 import { tryRequire, dedupe } from './lib/util';
-import babelLoader from './lib/babel-loader';
+import { getDefaultBabelLoader } from './lib/babel-loader';
 import cssLoader from './lib/css-loader';
 
 /**
@@ -104,6 +104,32 @@ export function addWebpackConfig(karmaConfig, pkg, options) {
 		return Object.assign({}, configured || {}, value);
 	}
 
+	let babelLoader = getLoader((rule) =>
+		`${rule.use},${rule.loader}`.match(/\bbabel-loader\b/)
+	);
+	if (babelLoader) {
+		if (options.coverage) {
+			if (babelLoader.loader.query) {
+				babelLoader.loader.query.plugins = [
+					...(babelLoader.loader.query?.plugins ?? []),
+					require.resolve('babel-plugin-istanbul'),
+				];
+			} else {
+				babelLoader.loader.options = babelLoader.loader.options || {};
+				babelLoader.loader.options.plugins = [
+					...(babelLoader.loader.options?.plugins ?? []),
+					require.resolve('babel-plugin-istanbul'),
+				];
+			}
+		}
+	} else {
+		loaders.push(getDefaultBabelLoader(options));
+	}
+
+	if (!getLoader('foo.css')) {
+		loaders.push(cssLoader(options));
+	}
+
 	for (let prop of Object.keys(karmaConfig.preprocessors)) {
 		karmaConfig.preprocessors[prop].unshift('webpack');
 	}
@@ -115,21 +141,7 @@ export function addWebpackConfig(karmaConfig, pkg, options) {
 		// devtool: 'module-source-map',
 		mode: webpackConfig.mode || 'development',
 		module: {
-			// @TODO check webpack version and use loaders VS rules as the key here appropriately:
-			//
-			// TODO: Consider adding coverage as a separate babel-loader so that
-			// regardless if the user provides their own babel plugins, coverage still
-			// works
-			rules: loaders
-				.concat(
-					!getLoader((rule) =>
-						`${rule.use},${rule.loader}`.match(/\bbabel-loader\b/)
-					)
-						? babelLoader(options)
-						: false,
-					!getLoader('foo.css') && cssLoader(options)
-				)
-				.filter(Boolean),
+			rules: loaders,
 		},
 		resolve: webpackProp('resolve', {
 			modules: webpackProp('resolve.modules', [