diff --git a/karma.conf.js b/karma.conf.js
index 54380ebd..a019887f 100644
--- a/karma.conf.js
+++ b/karma.conf.js
@@ -44,7 +44,7 @@ module.exports = (config) => {
       { pattern: 'tests/test.*.js', type: 'module' },
       // test support files
       { pattern: 'tests/fake.*.js', included: false, type: 'module' },
-      { pattern: 'tests/assertions.js', type: 'module' },
+      { pattern: 'tests/assertions.js', included: false, type: 'module' },
     ],
 
     client: {
diff --git a/tests/test.copyrect.js b/tests/test.copyrect.js
index 82a9bf36..ad9f8b31 100644
--- a/tests/test.copyrect.js
+++ b/tests/test.copyrect.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 
 import Websock from '../core/websock.js';
diff --git a/tests/test.deflator.js b/tests/test.deflator.js
index 2da03823..76c4d8f1 100644
--- a/tests/test.deflator.js
+++ b/tests/test.deflator.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 
 import { inflateInit, inflate } from "../vendor/pako/lib/zlib/inflate.js";
diff --git a/tests/test.display.js b/tests/test.display.js
index 48e90a43..131e76d1 100644
--- a/tests/test.display.js
+++ b/tests/test.display.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 import sinon from '../node_modules/sinon/pkg/sinon-esm.js';
 
diff --git a/tests/test.gesturehandler.js b/tests/test.gesturehandler.js
index e3c2e32a..880cdd14 100644
--- a/tests/test.gesturehandler.js
+++ b/tests/test.gesturehandler.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 import sinon from '../node_modules/sinon/pkg/sinon-esm.js';
 
diff --git a/tests/test.hextile.js b/tests/test.hextile.js
index 3fea3023..5a59e97b 100644
--- a/tests/test.hextile.js
+++ b/tests/test.hextile.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 
 import Websock from '../core/websock.js';
diff --git a/tests/test.inflator.js b/tests/test.inflator.js
index 8bf4f6f3..b1ebb722 100644
--- a/tests/test.inflator.js
+++ b/tests/test.inflator.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 
 import { deflateInit, deflate, Z_FULL_FLUSH } from "../vendor/pako/lib/zlib/deflate.js";
diff --git a/tests/test.jpeg.js b/tests/test.jpeg.js
index 4340242f..b50f22a5 100644
--- a/tests/test.jpeg.js
+++ b/tests/test.jpeg.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 
 import Websock from '../core/websock.js';
diff --git a/tests/test.keyboard.js b/tests/test.keyboard.js
index 4296486f..d7c4de8a 100644
--- a/tests/test.keyboard.js
+++ b/tests/test.keyboard.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 import sinon from '../node_modules/sinon/pkg/sinon-esm.js';
 
diff --git a/tests/test.localization.js b/tests/test.localization.js
index e49a0735..2d05d1c6 100644
--- a/tests/test.localization.js
+++ b/tests/test.localization.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 import sinon from '../node_modules/sinon/pkg/sinon-esm.js';
 
diff --git a/tests/test.raw.js b/tests/test.raw.js
index e3d8b457..2c62916d 100644
--- a/tests/test.raw.js
+++ b/tests/test.raw.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 
 import Websock from '../core/websock.js';
diff --git a/tests/test.rfb.js b/tests/test.rfb.js
index b4d59e02..e7c55b28 100644
--- a/tests/test.rfb.js
+++ b/tests/test.rfb.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 import sinon from '../node_modules/sinon/pkg/sinon-esm.js';
 
diff --git a/tests/test.rre.js b/tests/test.rre.js
index 5ca0d732..9ad931bc 100644
--- a/tests/test.rre.js
+++ b/tests/test.rre.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 
 import Websock from '../core/websock.js';
diff --git a/tests/test.tight.js b/tests/test.tight.js
index 28080bf4..bfa30d64 100644
--- a/tests/test.tight.js
+++ b/tests/test.tight.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 
 import Websock from '../core/websock.js';
diff --git a/tests/test.tightpng.js b/tests/test.tightpng.js
index 01d2493e..a52cfd5d 100644
--- a/tests/test.tightpng.js
+++ b/tests/test.tightpng.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 
 import Websock from '../core/websock.js';
diff --git a/tests/test.util.js b/tests/test.util.js
index 16dbb7c9..f836f4b2 100644
--- a/tests/test.util.js
+++ b/tests/test.util.js
@@ -1,4 +1,5 @@
 /* eslint-disable no-console */
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 import sinon from '../node_modules/sinon/pkg/sinon-esm.js';
 
diff --git a/tests/test.websock.js b/tests/test.websock.js
index 38b654a8..3509b36e 100644
--- a/tests/test.websock.js
+++ b/tests/test.websock.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 import sinon from '../node_modules/sinon/pkg/sinon-esm.js';
 
diff --git a/tests/test.webutil.js b/tests/test.webutil.js
index 45c71e49..6046c3f0 100644
--- a/tests/test.webutil.js
+++ b/tests/test.webutil.js
@@ -1,5 +1,6 @@
 /* jshint expr: true */
 
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 import sinon from '../node_modules/sinon/pkg/sinon-esm.js';
 
diff --git a/tests/test.zrle.js b/tests/test.zrle.js
index 679b4ad3..27e2a02c 100644
--- a/tests/test.zrle.js
+++ b/tests/test.zrle.js
@@ -1,3 +1,4 @@
+import './assertions.js';
 import { expect } from '../node_modules/chai/chai.js';
 
 import Websock from '../core/websock.js';