diff --git a/addons/addon-ligatures/src/index.test.ts b/addons/addon-ligatures/test/LigaturesAddon.test.ts
similarity index 90%
rename from addons/addon-ligatures/src/index.test.ts
rename to addons/addon-ligatures/test/LigaturesAddon.test.ts
index 1250e10e..ece5145c 100644
--- a/addons/addon-ligatures/src/index.test.ts
+++ b/addons/addon-ligatures/test/LigaturesAddon.test.ts
@@ -5,9 +5,13 @@
 
 import * as path from 'path';
 import { assert } from 'chai';
-import * as fontFinder from 'font-finder';
 
-import * as ligatureSupport from '.';
+// Use require to get a mutable module object (ESM imports create read-only bindings)
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+const fontFinder = require('font-finder');
+
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+const ligatureSupport = require('../out-esbuild/index');
 
 const originalList = fontFinder.list;
 
@@ -18,7 +22,7 @@ describe('LigaturesAddon', () => {
   const input = 'a -> b www c';
 
   before(() => {
-    (fontFinder as any).list = () => Promise.resolve({
+    fontFinder.list = () => Promise.resolve({
       'Fira Code': [{
         path: path.join(__dirname, '../fonts/firaCode.otf'),
         style: fontFinder.Style.Regular,
@@ -37,11 +41,11 @@ describe('LigaturesAddon', () => {
         type: fontFinder.Type.Monospace,
         weight: 400
       }]
-    } as fontFinder.FontList);
+    });
   });
 
   after(() => {
-    (fontFinder as any).list = originalList;
+    fontFinder.list = originalList;
   });
 
   beforeEach(() => {
diff --git a/addons/addon-ligatures/src/parse.test.ts b/addons/addon-ligatures/test/parse.test.ts
similarity index 95%
rename from addons/addon-ligatures/src/parse.test.ts
rename to addons/addon-ligatures/test/parse.test.ts
index 99dec083..98932883 100644
--- a/addons/addon-ligatures/src/parse.test.ts
+++ b/addons/addon-ligatures/test/parse.test.ts
@@ -5,7 +5,8 @@
 
 import { assert } from 'chai';
 
-import parse from './parse';
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+const parse = require('../out-esbuild/parse').default;
 
 // TODO: integrate tests from http://test.csswg.org/suites/css-fonts-4_dev/nightly-unstable/
 describe('parse', () => {
diff --git a/addons/addon-ligatures/test/tsconfig.json b/addons/addon-ligatures/test/tsconfig.json
new file mode 100644
index 00000000..ca68b468
--- /dev/null
+++ b/addons/addon-ligatures/test/tsconfig.json
@@ -0,0 +1,23 @@
+{
+  "compilerOptions": {
+    "module": "commonjs",
+    "target": "ESNext",
+    "lib": [
+      "es2021"
+    ],
+    "rootDir": ".",
+    "outDir": "../out-esbuild-test",
+    "sourceMap": true,
+    "removeComments": true,
+    "baseUrl": ".",
+    "strict": true,
+    "types": [
+      "../../../node_modules/@types/mocha",
+      "../../../node_modules/@types/node"
+    ]
+  },
+  "include": [
+    "./**/*",
+    "../../../typings/xterm.d.ts"
+  ]
+}
diff --git a/addons/addon-ligatures/tsconfig.json b/addons/addon-ligatures/tsconfig.json
index b711f30a..2d820dd1 100644
--- a/addons/addon-ligatures/tsconfig.json
+++ b/addons/addon-ligatures/tsconfig.json
@@ -2,6 +2,7 @@
   "files": [],
   "include": [],
   "references": [
-    { "path": "./src" }
+    { "path": "./src" },
+    { "path": "./test" }
   ]
 }