diff --git a/tests/shared/file-extensions.spec.js b/tests/shared/file-extensions.spec.js
deleted file mode 100644
index 3d43aca8..00000000
--- a/tests/shared/file-extensions.spec.js
+++ /dev/null
@@ -1,138 +0,0 @@
-/*
- * Copyright 2017 balena.io
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-'use strict'
-
-const m = require('mochainon')
-const _ = require('lodash')
-// eslint-disable-next-line node/no-missing-require
-const fileExtensions = require('../../lib/shared/file-extensions')
-
-describe('Shared: fileExtensions', function () {
-  describe('.getFileExtensions()', function () {
-    _.forEach([
-
-      // No extension
-      {
-        file: 'path/to/filename',
-        extensions: []
-      },
-
-      // Type: 'archive'
-      {
-        file: 'path/to/filename.zip',
-        extensions: [ 'zip' ]
-      },
-      {
-        file: 'path/to/filename.etch',
-        extensions: [ 'etch' ]
-      },
-
-      // Type: 'compressed'
-      {
-        file: 'path/to/filename.img.gz',
-        extensions: [ 'img', 'gz' ]
-      },
-      {
-        file: 'path/to/filename.img.bz2',
-        extensions: [ 'img', 'bz2' ]
-      },
-      {
-        file: 'path/to/filename.img.xz',
-        extensions: [ 'img', 'xz' ]
-      },
-      {
-        file: 'path/to/filename.img.xz.gz',
-        extensions: [ 'img', 'xz', 'gz' ]
-      },
-
-      // Type: 'image'
-      {
-        file: 'path/to/filename.img',
-        extensions: [ 'img' ]
-      },
-      {
-        file: 'path/to/filename.iso',
-        extensions: [ 'iso' ]
-      },
-      {
-        file: 'path/to/filename.dsk',
-        extensions: [ 'dsk' ]
-      },
-      {
-        file: 'path/to/filename.hddimg',
-        extensions: [ 'hddimg' ]
-      },
-      {
-        file: 'path/to/filename.raw',
-        extensions: [ 'raw' ]
-      },
-      {
-        file: 'path/to/filename.dmg',
-        extensions: [ 'dmg' ]
-      }
-
-    ], (testCase) => {
-      it(`should return ${testCase.extensions} for ${testCase.file}`, function () {
-        m.chai.expect(fileExtensions.getFileExtensions(testCase.file)).to.deep.equal(testCase.extensions)
-      })
-    })
-
-    it('should always return lowercase extensions', function () {
-      const filePath = 'foo.IMG.gZ'
-      m.chai.expect(fileExtensions.getFileExtensions(filePath)).to.deep.equal([
-        'img',
-        'gz'
-      ])
-    })
-  })
-
-  describe('.getLastFileExtension()', function () {
-    it('should return undefined if the file path has no extension', function () {
-      m.chai.expect(fileExtensions.getLastFileExtension('foo')).to.equal(null)
-    })
-
-    it('should return the extension if there is only one extension', function () {
-      m.chai.expect(fileExtensions.getLastFileExtension('foo.img')).to.equal('img')
-    })
-
-    it('should return the last extension if there are two extensions', function () {
-      m.chai.expect(fileExtensions.getLastFileExtension('foo.img.gz')).to.equal('gz')
-    })
-
-    it('should return the last extension if there are three extensions', function () {
-      m.chai.expect(fileExtensions.getLastFileExtension('foo.bar.img.gz')).to.equal('gz')
-    })
-  })
-
-  describe('.getPenultimateFileExtension()', function () {
-    it('should return undefined in the file path has no extension', function () {
-      m.chai.expect(fileExtensions.getPenultimateFileExtension('foo')).to.equal(null)
-    })
-
-    it('should return undefined if there is only one extension', function () {
-      m.chai.expect(fileExtensions.getPenultimateFileExtension('foo.img')).to.equal(null)
-    })
-
-    it('should return the penultimate extension if there are two extensions', function () {
-      m.chai.expect(fileExtensions.getPenultimateFileExtension('foo.img.gz')).to.equal('img')
-    })
-
-    it('should return the penultimate extension if there are three extensions', function () {
-      m.chai.expect(fileExtensions.getPenultimateFileExtension('foo.bar.img.gz')).to.equal('img')
-    })
-  })
-})
diff --git a/tests/shared/file-extensions.spec.ts b/tests/shared/file-extensions.spec.ts
new file mode 100644
index 00000000..2fd9963c
--- /dev/null
+++ b/tests/shared/file-extensions.spec.ts
@@ -0,0 +1,147 @@
+/*
+ * Copyright 2017 balena.io
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { expect } from 'chai';
+import * as _ from 'lodash';
+
+import * as fileExtensions from '../../lib/shared/file-extensions';
+
+describe('Shared: fileExtensions', function() {
+	describe('.getFileExtensions()', function() {
+		_.forEach(
+			[
+				// No extension
+				{
+					file: 'path/to/filename',
+					extensions: [],
+				},
+
+				// Type: 'archive'
+				{
+					file: 'path/to/filename.zip',
+					extensions: ['zip'],
+				},
+				{
+					file: 'path/to/filename.etch',
+					extensions: ['etch'],
+				},
+
+				// Type: 'compressed'
+				{
+					file: 'path/to/filename.img.gz',
+					extensions: ['img', 'gz'],
+				},
+				{
+					file: 'path/to/filename.img.bz2',
+					extensions: ['img', 'bz2'],
+				},
+				{
+					file: 'path/to/filename.img.xz',
+					extensions: ['img', 'xz'],
+				},
+				{
+					file: 'path/to/filename.img.xz.gz',
+					extensions: ['img', 'xz', 'gz'],
+				},
+
+				// Type: 'image'
+				{
+					file: 'path/to/filename.img',
+					extensions: ['img'],
+				},
+				{
+					file: 'path/to/filename.iso',
+					extensions: ['iso'],
+				},
+				{
+					file: 'path/to/filename.dsk',
+					extensions: ['dsk'],
+				},
+				{
+					file: 'path/to/filename.hddimg',
+					extensions: ['hddimg'],
+				},
+				{
+					file: 'path/to/filename.raw',
+					extensions: ['raw'],
+				},
+				{
+					file: 'path/to/filename.dmg',
+					extensions: ['dmg'],
+				},
+			],
+			testCase => {
+				it(`should return ${testCase.extensions} for ${testCase.file}`, function() {
+					expect(fileExtensions.getFileExtensions(testCase.file)).to.deep.equal(
+						testCase.extensions,
+					);
+				});
+			},
+		);
+
+		it('should always return lowercase extensions', function() {
+			const filePath = 'foo.IMG.gZ';
+			expect(fileExtensions.getFileExtensions(filePath)).to.deep.equal([
+				'img',
+				'gz',
+			]);
+		});
+	});
+
+	describe('.getLastFileExtension()', function() {
+		it('should return undefined if the file path has no extension', function() {
+			expect(fileExtensions.getLastFileExtension('foo')).to.equal(null);
+		});
+
+		it('should return the extension if there is only one extension', function() {
+			expect(fileExtensions.getLastFileExtension('foo.img')).to.equal('img');
+		});
+
+		it('should return the last extension if there are two extensions', function() {
+			expect(fileExtensions.getLastFileExtension('foo.img.gz')).to.equal('gz');
+		});
+
+		it('should return the last extension if there are three extensions', function() {
+			expect(fileExtensions.getLastFileExtension('foo.bar.img.gz')).to.equal(
+				'gz',
+			);
+		});
+	});
+
+	describe('.getPenultimateFileExtension()', function() {
+		it('should return undefined in the file path has no extension', function() {
+			expect(fileExtensions.getPenultimateFileExtension('foo')).to.equal(null);
+		});
+
+		it('should return undefined if there is only one extension', function() {
+			expect(fileExtensions.getPenultimateFileExtension('foo.img')).to.equal(
+				null,
+			);
+		});
+
+		it('should return the penultimate extension if there are two extensions', function() {
+			expect(fileExtensions.getPenultimateFileExtension('foo.img.gz')).to.equal(
+				'img',
+			);
+		});
+
+		it('should return the penultimate extension if there are three extensions', function() {
+			expect(
+				fileExtensions.getPenultimateFileExtension('foo.bar.img.gz'),
+			).to.equal('img');
+		});
+	});
+});