diff --git a/test/modules/types/mime_test.js b/test/modules/types/mime_test.js
deleted file mode 100644
index 947fa6a29..000000000
--- a/test/modules/types/mime_test.js
+++ /dev/null
@@ -1,31 +0,0 @@
-// Copyright 2018-2020 Signal Messenger, LLC
-// SPDX-License-Identifier: AGPL-3.0-only
-
-const { assert } = require('chai');
-
-const MIME = require('../../../ts/types/MIME');
-
-describe('MIME', () => {
-  describe('isJPEG', () => {
-    it('should return true for `image/jpeg`', () => {
-      assert.isTrue(MIME.isJPEG('image/jpeg'));
-    });
-
-    [
-      'jpg',
-      'jpeg',
-      'image/jpg', // invalid MIME type: https://stackoverflow.com/a/37266399/125305
-      'image/gif',
-      'image/tiff',
-      'application/json',
-      0,
-      false,
-      null,
-      undefined,
-    ].forEach(value => {
-      it(`should return false for \`${value}\``, () => {
-        assert.isFalse(MIME.isJPEG(value));
-      });
-    });
-  });
-});
diff --git a/test/modules/link_previews_test.js b/ts/test-node/types/LinkPreview_test.ts
similarity index 98%
rename from test/modules/link_previews_test.js
rename to ts/test-node/types/LinkPreview_test.ts
index c632ef2af..67d5c56f9 100644
--- a/test/modules/link_previews_test.js
+++ b/ts/test-node/types/LinkPreview_test.ts
@@ -1,13 +1,13 @@
-// Copyright 2019-2020 Signal Messenger, LLC
+// Copyright 2019-2022 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
-const { assert } = require('chai');
+import { assert } from 'chai';
 
-const {
+import {
   findLinks,
   isLinkSafeToPreview,
   isLinkSneaky,
-} = require('../../ts/types/LinkPreview');
+} from '../../types/LinkPreview';
 
 describe('Link previews', () => {
   describe('#isLinkSafeToPreview', () => {
diff --git a/ts/test-node/types/MIME_test.ts b/ts/test-node/types/MIME_test.ts
index 0f3b18a48..970e0b212 100644
--- a/ts/test-node/types/MIME_test.ts
+++ b/ts/test-node/types/MIME_test.ts
@@ -1,4 +1,4 @@
-// Copyright 2021 Signal Messenger, LLC
+// Copyright 2018-2022 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import { assert } from 'chai';
@@ -12,11 +12,29 @@ describe('MIME', () => {
     });
 
     it('returns false for non-GIFs', () => {
+      assert.isFalse(MIME.isGif(''));
+      assert.isFalse(MIME.isGif('gif'));
       assert.isFalse(MIME.isGif('image/jpeg'));
       assert.isFalse(MIME.isGif('text/plain'));
     });
   });
 
+  describe('isJPEG', () => {
+    it('should return true for `image/jpeg`', () => {
+      assert.isTrue(MIME.isJPEG('image/jpeg'));
+    });
+
+    it('returns false for non-JPEGs', () => {
+      assert.isFalse(MIME.isJPEG(''));
+      assert.isFalse(MIME.isJPEG('jpg'));
+      assert.isFalse(MIME.isJPEG('jpeg'));
+      assert.isFalse(MIME.isJPEG('image/jpg')); // invalid MIME type: https://stackoverflow.com/a/37266399/125305
+      assert.isFalse(MIME.isJPEG('image/gif'));
+      assert.isFalse(MIME.isJPEG('image/tiff'));
+      assert.isFalse(MIME.isJPEG('application/json'));
+    });
+  });
+
   describe('isLongMessage', () => {
     it('returns true for long messages', () => {
       assert.isTrue(MIME.isLongMessage('text/x-signal-plain'));