diff --git a/bunfig.toml b/bunfig.toml
new file mode 100644
index 0000000..f9e1944
--- /dev/null
+++ b/bunfig.toml
@@ -0,0 +1,3 @@
+[test]
+# Load these modules before running tests.
+preload = ["./test/preload.ts"]
\ No newline at end of file
diff --git a/src/utils/compose.ts b/src/utils/compose.ts
index 1c7828c..51309cf 100644
--- a/src/utils/compose.ts
+++ b/src/utils/compose.ts
@@ -1,4 +1,4 @@
-import * as fs from 'node:fs';
+import fs from 'node:fs';
 import * as path from 'node:path';
 import { projectConfig } from '../config/project';
 import { cmd as $ } from './cmd';
diff --git a/test/preload.ts b/test/preload.ts
new file mode 100644
index 0000000..96b946c
--- /dev/null
+++ b/test/preload.ts
@@ -0,0 +1,19 @@
+import { mock } from 'bun:test';
+
+mock.module('node:fs', () => ({
+  default: {
+    readdirSync: (dir: string) => {
+      switch (true) {
+        case dir.includes('frontend'):
+          return ['compose-frontend.yml'];
+        case dir.includes('backend'):
+          return ['compose-backend.yml'];
+        default:
+          return ['compose.yml'];
+      }
+    },
+    existsSync: (path: string) => true,
+    lstatSync: (path: string) => ({ isFile: () => true }),
+    readFileSync: (path: string) => '',
+  },
+}));
diff --git a/test/utils/compose.test.ts b/test/utils/compose.test.ts
new file mode 100644
index 0000000..f4515ad
--- /dev/null
+++ b/test/utils/compose.test.ts
@@ -0,0 +1,21 @@
+import { describe, expect, mock, test } from 'bun:test';
+import { composeFiles } from '../../src/utils/compose.ts';
+
+mock.module('../../src/utils/git.ts', () => ({
+  validateLocalGitRepo: () => null,
+}));
+
+describe('Utils: compose', () => {
+  test('composeFiles returns the correct output', () => {
+    const output = composeFiles({
+      filesDir: '.dems',
+      prefix: 'compose.+.',
+      repos: ['frontend', 'backend'],
+      reposRoot: '/projects',
+    });
+    expect(output).toEqual([
+      '--file /projects/frontend/.dems/compose-frontend.yml',
+      '--file /projects/backend/.dems/compose-backend.yml',
+    ]);
+  });
+});