diff --git a/packages/browser-test-runner/src/createKarmaConfig.ts b/packages/browser-test-runner/src/createKarmaConfig.ts
index 14f8e34f7e..38d09d8285 100644
--- a/packages/browser-test-runner/src/createKarmaConfig.ts
+++ b/packages/browser-test-runner/src/createKarmaConfig.ts
@@ -1,19 +1,40 @@
 import fs from 'fs'
+import type { Configuration, ExternalItem } from 'webpack'
 
 const DEBUG_MODE = process.env.BROWSER_TEST_DEBUG_MODE ?? false
 
 export const createKarmaConfig = (
-    testPaths: string[], webpackConfig: () => Record<string, any>, localDirectory: string
+    testPaths: string[], webpackConfig: () => Configuration, localDirectory?: string
 ): (config: any) => any => {
     const setupFiles = [__dirname + '/karma-setup.js']
-    const localSetupFile = localDirectory + '/karma-setup.js'
-    if (fs.existsSync(localSetupFile)) {
-        setupFiles.push(localSetupFile)
+
+    if (localDirectory !== undefined) {
+        const localSetupFile = localDirectory + '/karma-setup.js'
+        if (fs.existsSync(localSetupFile)) {
+            setupFiles.push(localSetupFile)
+        }
     }
+
     const preprocessors: Record<string, string[]> = {}
     setupFiles.forEach((f) => preprocessors[f] = ['webpack'])
     testPaths.forEach((f) => preprocessors[f] = ['webpack', 'sourcemap'])
     const baseWebpack = webpackConfig()
+
+    const mergedExternals: ExternalItem[] = []
+    if (baseWebpack.externals !== undefined) {
+        if (Array.isArray(baseWebpack.externals)) {
+            mergedExternals.push(...baseWebpack.externals)
+        } else {
+            mergedExternals.push(baseWebpack.externals)
+        }
+    }
+    mergedExternals.push({
+        'expect': 'commonjs2 expect',
+        '@jest/expect-utils': 'commonjs2 @jest/expect-utils',
+        'pretty-format': 'commonjs2 pretty-format',
+        'jest-diff': 'commonjs2 jest-diff',
+    })
+
     return (config: any) => {
         config.set({
             plugins: [
@@ -56,13 +77,7 @@ export const createKarmaConfig = (
             singleRun: !DEBUG_MODE,  //set to false to leave electron window open
             webpack: {
                 ...baseWebpack,
-                externals: {
-                    ...(baseWebpack.externals ?? {}),
-                    'expect': 'commonjs2 expect',
-                    '@jest/expect-utils': 'commonjs2 @jest/expect-utils',
-                    'pretty-format': 'commonjs2 pretty-format',
-                    'jest-diff': 'commonjs2 jest-diff',
-                },
+                externals: mergedExternals,
             }
         })
     }
diff --git a/packages/browser-test-runner/src/createWebpackConfig.ts b/packages/browser-test-runner/src/createWebpackConfig.ts
index 6920c9b169..293d89f9d6 100644
--- a/packages/browser-test-runner/src/createWebpackConfig.ts
+++ b/packages/browser-test-runner/src/createWebpackConfig.ts
@@ -1,17 +1,19 @@
 import path from 'path'
-import webpack from 'webpack'
+import webpack, { type Configuration } from 'webpack'
 import NodePolyfillPlugin from 'node-polyfill-webpack-plugin'
 
 interface CreateWebpackConfigOptions {
     libraryName: string
-    alias?: Record<string, string>
-    fallback?: Record<string, string>
-    externals?: Record<string, string>
+    alias?: webpack.ResolveOptions['alias']
+    fallback?: webpack.ResolveOptions['fallback']
+    externals?: webpack.Externals
 }
 
+type CreateWebpackConfigReturnType = () => Configuration
+
 export const createWebpackConfig = (
     { libraryName, alias = {}, fallback = {}, externals = {} }: CreateWebpackConfigOptions
-): Record<string, any> => {
+): CreateWebpackConfigReturnType => {
     return () => {
         return {
             cache: {
diff --git a/packages/dht/karma.config.js b/packages/dht/karma.config.ts
similarity index 51%
rename from packages/dht/karma.config.js
rename to packages/dht/karma.config.ts
index ce05384d34..505d61e569 100644
--- a/packages/dht/karma.config.js
+++ b/packages/dht/karma.config.ts
@@ -1,6 +1,5 @@
-/* eslint-disable @typescript-eslint/no-require-imports */
-const path = require('path')
-const { createKarmaConfig, createWebpackConfig } = require('@streamr/browser-test-runner')
+import { resolve } from 'path'
+import { createKarmaConfig, createWebpackConfig } from '@streamr/browser-test-runner'
 
 const TEST_PATHS = [
     'test/unit/**/!(connectivityRequestHandler*).ts',
@@ -8,12 +7,12 @@ const TEST_PATHS = [
     './test/end-to-end/**/!(RecoveryFromFailedAutoCertification*|memory-leak*|GeoIpLayer0*).ts'
 ]
 
-const NodeWebrtcConnection = path.resolve(__dirname, 'src/connection/webrtc/NodeWebrtcConnection.ts')
-const BrowserWebrtcConnection = path.resolve(__dirname, 'src/connection/webrtc/BrowserWebrtcConnection.ts')
-const NodeWebsocketClientConnection = path.resolve(__dirname, 'src/connection/websocket/NodeWebsocketClientConnection.ts')
-const BrowserWebsocketClientConnection = path.resolve(__dirname, 'src/connection/websocket/BrowserWebsocketClientConnection.ts')
+const NodeWebrtcConnection = resolve(__dirname, 'src/connection/webrtc/NodeWebrtcConnection.ts')
+const BrowserWebrtcConnection = resolve(__dirname, 'src/connection/webrtc/BrowserWebrtcConnection.ts')
+const NodeWebsocketClientConnection = resolve(__dirname, 'src/connection/websocket/NodeWebsocketClientConnection.ts')
+const BrowserWebsocketClientConnection = resolve(__dirname, 'src/connection/websocket/BrowserWebsocketClientConnection.ts')
 
-module.exports = createKarmaConfig(
+export default createKarmaConfig(
     TEST_PATHS,
     createWebpackConfig({
         libraryName: 'dht',
diff --git a/packages/dht/package.json b/packages/dht/package.json
index 85c7dd200b..49e1684ec6 100644
--- a/packages/dht/package.json
+++ b/packages/dht/package.json
@@ -30,7 +30,7 @@
     "clean": "jest --clearCache || true; rm -rf dist *.tsbuildinfo node_modules/.cache || true",
     "eslint": "eslint --cache --cache-location=node_modules/.cache/.eslintcache/ '*/**/*.{js,ts}'",
     "test": "npm run test-unit && npm run test-integration && npm run test-end-to-end",
-    "test-browser": "karma start karma.config.js",
+    "test-browser": "karma start karma.config.ts",
     "test-unit": "jest test/unit",
     "test-integration": "jest --bail test/integration",
     "test-end-to-end": "jest --bail test/end-to-end",
diff --git a/packages/proto-rpc/karma.config.js b/packages/proto-rpc/karma.config.js
deleted file mode 100644
index e0b4f2c1a4..0000000000
--- a/packages/proto-rpc/karma.config.js
+++ /dev/null
@@ -1,11 +0,0 @@
-// eslint-disable-next-line @typescript-eslint/no-require-imports
-const { createKarmaConfig, createWebpackConfig } = require('@streamr/browser-test-runner')
-
-const TEST_PATHS = ['test/**/*.ts']
-
-module.exports = createKarmaConfig(TEST_PATHS, createWebpackConfig({
-    libraryName: 'proto-rpc',
-    fallback: {
-        module: false
-    }
-}))
diff --git a/packages/proto-rpc/karma.config.ts b/packages/proto-rpc/karma.config.ts
new file mode 100644
index 0000000000..3bae5dd158
--- /dev/null
+++ b/packages/proto-rpc/karma.config.ts
@@ -0,0 +1,10 @@
+import { createKarmaConfig, createWebpackConfig } from '@streamr/browser-test-runner'
+
+const TEST_PATHS = ['test/**/*.ts']
+
+export default createKarmaConfig(TEST_PATHS, createWebpackConfig({
+    libraryName: 'proto-rpc',
+    fallback: {
+        module: false
+    }
+}))
diff --git a/packages/proto-rpc/package.json b/packages/proto-rpc/package.json
index c63d749d14..ebb0e24bb0 100644
--- a/packages/proto-rpc/package.json
+++ b/packages/proto-rpc/package.json
@@ -25,7 +25,7 @@
     "clean": "jest --clearCache || true; rm -rf dist *.tsbuildinfo node_modules/.cache || true",
     "eslint": "./test-proto.sh && eslint --cache --cache-location=node_modules/.cache/.eslintcache/ '*/**/*.{js,ts}'",
     "test": "./test-proto.sh && npm run test-unit && npm run test-integration",
-    "test-browser": "./test-proto.sh && karma start karma.config.js",
+    "test-browser": "./test-proto.sh && karma start karma.config.ts",
     "test-unit": "./test-proto.sh && jest test/unit",
     "test-integration": "./test-proto.sh && jest --bail test/integration"
   },
diff --git a/packages/sdk/karma-end-to-end.config.js b/packages/sdk/karma-end-to-end.config.js
deleted file mode 100644
index 9dbebea2ca..0000000000
--- a/packages/sdk/karma-end-to-end.config.js
+++ /dev/null
@@ -1,5 +0,0 @@
-/* eslint-disable @typescript-eslint/no-require-imports */
-const webpackConfig = require('./webpack-karma.config')
-const { createKarmaConfig } = require('@streamr/browser-test-runner')
-
-module.exports = createKarmaConfig(['test/end-to-end/**/*.ts'], webpackConfig, __dirname)
diff --git a/packages/sdk/karma-end-to-end.config.ts b/packages/sdk/karma-end-to-end.config.ts
new file mode 100644
index 0000000000..4cdf76f6ec
--- /dev/null
+++ b/packages/sdk/karma-end-to-end.config.ts
@@ -0,0 +1,4 @@
+import webpackConfig from './webpack-karma.config'
+import { createKarmaConfig } from '@streamr/browser-test-runner'
+
+export default createKarmaConfig(['test/end-to-end/**/*.ts'], webpackConfig, __dirname)
diff --git a/packages/sdk/karma-integration.config.js b/packages/sdk/karma-integration.config.js
deleted file mode 100644
index 8ae7fc1f5d..0000000000
--- a/packages/sdk/karma-integration.config.js
+++ /dev/null
@@ -1,5 +0,0 @@
-/* eslint-disable @typescript-eslint/no-require-imports */
-const webpackConfig = require('./webpack-karma.config')
-const { createKarmaConfig } = require('@streamr/browser-test-runner')
-
-module.exports = createKarmaConfig(['test/integration/**/*.ts'], webpackConfig, __dirname)
diff --git a/packages/sdk/karma-integration.config.ts b/packages/sdk/karma-integration.config.ts
new file mode 100644
index 0000000000..b2848a6117
--- /dev/null
+++ b/packages/sdk/karma-integration.config.ts
@@ -0,0 +1,4 @@
+import webpackConfig from './webpack-karma.config'
+import { createKarmaConfig } from '@streamr/browser-test-runner'
+
+export default createKarmaConfig(['test/integration/**/*.ts'], webpackConfig, __dirname)
diff --git a/packages/sdk/karma-setup.js b/packages/sdk/karma-setup.js
index 43dd7d02df..c65072a44a 100644
--- a/packages/sdk/karma-setup.js
+++ b/packages/sdk/karma-setup.js
@@ -3,8 +3,7 @@
  * package. See karma-config.js in that package for more details.
  */
 
-// eslint-disable-next-line @typescript-eslint/no-require-imports
-require('./test/test-utils/customMatchers')
+import './test/test-utils/customMatchers'
+import { customMatchers } from '@streamr/test-utils'
 
-const { customMatchers } = require('@streamr/test-utils')
-expect.extend(customMatchers)
\ No newline at end of file
+expect.extend(customMatchers)
diff --git a/packages/sdk/karma-unit.config.js b/packages/sdk/karma-unit.config.js
deleted file mode 100644
index 097e80fd97..0000000000
--- a/packages/sdk/karma-unit.config.js
+++ /dev/null
@@ -1,5 +0,0 @@
-/* eslint-disable @typescript-eslint/no-require-imports */
-const webpackConfig = require('./webpack-karma.config')
-const { createKarmaConfig } = require('@streamr/browser-test-runner')
-
-module.exports = createKarmaConfig(['test/unit/**/*.ts'], webpackConfig, __dirname)
diff --git a/packages/sdk/karma-unit.config.ts b/packages/sdk/karma-unit.config.ts
new file mode 100644
index 0000000000..907753406d
--- /dev/null
+++ b/packages/sdk/karma-unit.config.ts
@@ -0,0 +1,4 @@
+import webpackConfig from './webpack-karma.config'
+import { createKarmaConfig } from '@streamr/browser-test-runner'
+
+export default createKarmaConfig(['test/unit/**/*.ts'], webpackConfig, __dirname)
diff --git a/packages/sdk/package.json b/packages/sdk/package.json
index 88908bd17a..c97018878b 100644
--- a/packages/sdk/package.json
+++ b/packages/sdk/package.json
@@ -44,9 +44,9 @@
     "test-unit": "jest --useStderr --forceExit test/unit",
     "test-integration": "jest --bail --useStderr --forceExit --testTimeout=40000 test/integration/*.test.*",
     "test-end-to-end": "jest --bail --useStderr --forceExit --testTimeout=40000 test/end-to-end/*.test.*",
-    "test-browser-unit": "karma start karma-unit.config.js",
-    "test-browser-integration": "karma start karma-integration.config.js",
-    "test-browser-end-to-end": "karma start karma-end-to-end.config.js",
+    "test-browser-unit": "karma start karma-unit.config.ts",
+    "test-browser-integration": "karma start karma-integration.config.ts",
+    "test-browser-end-to-end": "karma start karma-end-to-end.config.ts",
     "test-browser-smoke": "bash test/browser-smoke-test/smoke-test.sh",
     "test-exports": "cd test/exports && npm run link && tsc --noEmit --project ./tsconfig.json && npm test"
   },
diff --git a/packages/sdk/webpack-karma.config.js b/packages/sdk/webpack-karma.config.ts
similarity index 58%
rename from packages/sdk/webpack-karma.config.js
rename to packages/sdk/webpack-karma.config.ts
index 51d82b06b8..3b36c09dac 100644
--- a/packages/sdk/webpack-karma.config.js
+++ b/packages/sdk/webpack-karma.config.ts
@@ -1,7 +1,8 @@
-const defaultConfig = require('./webpack.config')
-const path = require('path')
+import type { Configuration } from 'webpack'
+import defaultConfig from './webpack.config'
+import path from 'path'
 
-module.exports = (env, argv) => {
+const karmaWebpackConfig: (env?: Record<string, unknown>, argv?: Record<string, unknown>) => Configuration = (env = {}, argv = {}) => {
     const config = defaultConfig(env, argv)
 
     return {
@@ -17,6 +18,8 @@ module.exports = (env, argv) => {
                 v8: false,
                 'jest-leak-detector': false,
             }
-        }
-    }
+        },
+    } as Configuration
 }
+
+export default karmaWebpackConfig
diff --git a/packages/sdk/webpack.config.js b/packages/sdk/webpack.config.js
index 4b93a3ca8f..d7005da143 100644
--- a/packages/sdk/webpack.config.js
+++ b/packages/sdk/webpack.config.js
@@ -52,6 +52,8 @@ module.exports = (env, argv) => {
             ]
         },
         resolve: {
+            alias: {},
+            fallback: {},
             modules: ['node_modules', ...require.resolve.paths('')],
             extensions: ['.json', '.js', '.ts'],
         },
diff --git a/packages/trackerless-network/karma-setup.js b/packages/trackerless-network/karma-setup.js
index c87bf6e6e5..4e1f75011f 100644
--- a/packages/trackerless-network/karma-setup.js
+++ b/packages/trackerless-network/karma-setup.js
@@ -3,5 +3,5 @@
  * package. See karma-config.js in that package for more details.
  */
 
-const { customMatchers } = require('@streamr/test-utils')
-expect.extend(customMatchers)
\ No newline at end of file
+import { customMatchers } from '@streamr/test-utils'
+expect.extend(customMatchers)
diff --git a/packages/trackerless-network/karma.config.js b/packages/trackerless-network/karma.config.js
deleted file mode 100644
index 692143b6a4..0000000000
--- a/packages/trackerless-network/karma.config.js
+++ /dev/null
@@ -1,30 +0,0 @@
-/* eslint-disable @typescript-eslint/no-require-imports */
-const path = require('path')
-const { createKarmaConfig, createWebpackConfig } = require('@streamr/browser-test-runner')
-
-const TEST_PATHS = [
-    './test/unit/**/*.ts',
-    './test/integration/**/*.ts',
-    './test/end-to-end/**/!(webrtc*|websocket*)',
-]
-
-module.exports = createKarmaConfig(TEST_PATHS, createWebpackConfig({
-    libraryName: 'trackerless-network',
-    alias: {
-        [path.resolve(__dirname, '../dht/src/connection/webrtc/NodeWebrtcConnection.ts')]:
-            path.resolve(__dirname, '../dht/src/connection/webrtc/BrowserWebrtcConnection.ts'),
-        [path.resolve(__dirname, '../dht/src/connection/websocket/NodeWebsocketClientConnection.ts')]:
-            path.resolve(__dirname, '../dht/src/connection/websocket/BrowserWebsocketClientConnection.ts'),
-        '@streamr/dht': path.resolve('../dht/src/exports.ts'),
-        '@streamr/proto-rpc': path.resolve('../proto-rpc/src/exports.ts'),
-    },
-    fallback: {
-        module: false
-    },
-    externals: {
-        'node-datachannel': 'commonjs node-datachannel',
-        express: 'Express',
-        http: 'HTTP',
-        ws: 'WebSocket',
-    }
-}), __dirname)
diff --git a/packages/trackerless-network/karma.config.ts b/packages/trackerless-network/karma.config.ts
new file mode 100644
index 0000000000..4d2fb6f2be
--- /dev/null
+++ b/packages/trackerless-network/karma.config.ts
@@ -0,0 +1,29 @@
+import { resolve } from 'path'
+import { createKarmaConfig, createWebpackConfig } from '@streamr/browser-test-runner'
+
+const TEST_PATHS = [
+    './test/unit/**/*.ts',
+    './test/integration/**/*.ts',
+    './test/end-to-end/**/!(webrtc*|websocket*)',
+]
+
+export default createKarmaConfig(TEST_PATHS, createWebpackConfig({
+    libraryName: 'trackerless-network',
+    alias: {
+        [resolve(__dirname, '../dht/src/connection/webrtc/NodeWebrtcConnection.ts')]:
+            resolve(__dirname, '../dht/src/connection/webrtc/BrowserWebrtcConnection.ts'),
+        [resolve(__dirname, '../dht/src/connection/websocket/NodeWebsocketClientConnection.ts')]:
+            resolve(__dirname, '../dht/src/connection/websocket/BrowserWebsocketClientConnection.ts'),
+        '@streamr/dht': resolve('../dht/src/exports.ts'),
+        '@streamr/proto-rpc': resolve('../proto-rpc/src/exports.ts'),
+    },
+    fallback: {
+        module: false
+    },
+    externals: {
+        'node-datachannel': 'commonjs node-datachannel',
+        express: 'Express',
+        http: 'HTTP',
+        ws: 'WebSocket',
+    }
+}), __dirname)
diff --git a/packages/trackerless-network/package.json b/packages/trackerless-network/package.json
index 85fcdd75e6..38597c80a4 100644
--- a/packages/trackerless-network/package.json
+++ b/packages/trackerless-network/package.json
@@ -26,7 +26,7 @@
     "coverage": "jest --coverage",
     "eslint": "eslint --cache --cache-location=node_modules/.cache/.eslintcache/ '*/**/*.{js,ts}'",
     "test": "npm run test-unit && npm run test-integration && npm run test-end-to-end",
-    "test-browser": "karma start karma.config.js",
+    "test-browser": "karma start karma.config.ts",
     "test-unit": "jest test/unit",
     "test-integration": "jest --bail test/integration",
     "test-end-to-end": "jest --bail test/end-to-end",
diff --git a/packages/utils/karma.config.js b/packages/utils/karma.config.js
deleted file mode 100644
index 7bbe1a2d31..0000000000
--- a/packages/utils/karma.config.js
+++ /dev/null
@@ -1,11 +0,0 @@
-// eslint-disable-next-line @typescript-eslint/no-require-imports
-const { createKarmaConfig, createWebpackConfig } = require('@streamr/browser-test-runner')
-
-const TEST_PATHS = ['test/**/*.ts']
-
-module.exports = createKarmaConfig(TEST_PATHS, createWebpackConfig({
-    libraryName: 'utils',
-    fallback: {
-        module: false
-    }
-}))
diff --git a/packages/utils/karma.config.ts b/packages/utils/karma.config.ts
new file mode 100644
index 0000000000..79cb15a828
--- /dev/null
+++ b/packages/utils/karma.config.ts
@@ -0,0 +1,10 @@
+import { createKarmaConfig, createWebpackConfig } from '@streamr/browser-test-runner'
+
+const TEST_PATHS = ['test/**/*.ts']
+
+export default createKarmaConfig(TEST_PATHS, createWebpackConfig({
+    libraryName: 'utils',
+    fallback: {
+        module: false
+    }
+}))
diff --git a/packages/utils/package.json b/packages/utils/package.json
index 81f5d087cd..619b5c3a87 100644
--- a/packages/utils/package.json
+++ b/packages/utils/package.json
@@ -21,7 +21,7 @@
     "clean": "jest --clearCache || true; rm -rf dist *.tsbuildinfo node_modules/.cache || true",
     "eslint": "eslint --cache --cache-location=node_modules/.cache/.eslintcache/ '*/**/*.{js,ts}'",
     "test": "jest",
-    "test-browser": "karma start karma.config.js"
+    "test-browser": "karma start karma.config.ts"
   },
   "author": "Streamr Network AG <contact@streamr.network>",
   "license": "Apache-2.0",