diff --git a/package.json b/package.json
index 1cfd20f..541e9a5 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "webpack-chain",
-  "version": "1.3.0",
+  "version": "1.4.0",
   "main": "src/Config.js",
   "repository": "mozilla-rpweb/webpack-chain",
   "keywords": [
diff --git a/src/Config.js b/src/Config.js
index a143ecb..b29d51c 100644
--- a/src/Config.js
+++ b/src/Config.js
@@ -22,6 +22,7 @@ class Config {
 
   externals(externals) {
     this.options.set('externals', externals);
+    return this;
   }
 
   devtool(devtool) {
diff --git a/src/Rule.js b/src/Rule.js
index 81c1c65..240e2c1 100644
--- a/src/Rule.js
+++ b/src/Rule.js
@@ -85,6 +85,10 @@ module.exports = class extends ChainedMap {
             return this.exclude(...value);
           }
 
+          case 'test': {
+            return this.test(new RegExp(value));
+          }
+
           case 'loader': {
             return Object
               .keys(value)