diff --git a/common/web/types/tests/util/file-types.tests.ts b/common/web/types/tests/util/file-types.tests.ts
new file mode 100644
index 00000000000..3f4d6870918
--- /dev/null
+++ b/common/web/types/tests/util/file-types.tests.ts
@@ -0,0 +1,234 @@
+/*
+ * Keyman is copyright (C) SIL Global. MIT License.
+ * 
+ * Created by Dr Mark C. Sinclair on 2024-11-29
+ * 
+ * Test code for file-types.ts
+ */
+
+import 'mocha';
+import { assert } from 'chai';
+import {
+  ALL,
+  ALL_SOURCE,
+  ALL_BINARY,
+  Binary,
+  fromFilename,
+  removeExtension,
+  sourceOrBinaryTypeFromFilename,
+  sourceTypeFromFilename,
+  binaryTypeFromFilename,
+  filenameIs,
+  replaceExtension,
+} from '../../src/util/file-types.js';
+
+describe('Test of File-Types', () => {
+  describe('Test of fromFilename()', () => {
+    it('can extract Source file extension', () => {
+      ALL_SOURCE.forEach((ext) => {
+        const filename = `file${ext}`;
+        const actual   = fromFilename(filename);
+        assert.deepEqual(actual, ext);
+      });
+    });
+    it('can extract Binary file extension', () => {
+      ALL_BINARY.forEach((ext) => {
+        const filename = `file${ext}`;
+        const actual   = fromFilename(filename);
+        assert.deepEqual(actual, ext);
+      });
+    });
+    it('can extract unmatched file extension', () => {
+      const ext = ".cpp";
+      assert.isFalse((Object.values(ALL_SOURCE) as string[]).includes(ext));
+      const filename = `file${ext}`;
+      const actual   = fromFilename(filename);
+      assert.deepEqual(actual, ext);
+    });
+    it('returns empty string for no file extension', () => {
+      const filename = `file`;
+      const actual   = fromFilename(filename);
+      assert.deepEqual(actual, "");
+    });
+    it('can extract upper case file extension', () => {
+      const ext          = ALL_SOURCE[0];
+      const upperCaseExt = ext.toUpperCase();
+      const filename     = `file${upperCaseExt}`;
+      const actual       = fromFilename(filename);
+      assert.deepEqual(actual, ext);
+    });
+  });
+  describe('Test of removeExtension()', () => {
+    it('can remove Source file extension', () => {
+      ALL_SOURCE.forEach((ext) => {
+        const filename = `file${ext}`;
+        const actual   = removeExtension(filename);
+        assert.deepEqual(actual, "file");
+      });
+    });
+    it('can remove Binary file extension', () => {
+      ALL_BINARY.forEach((ext) => {
+        const filename = `file${ext}`;
+        const actual   = removeExtension(filename);
+        assert.deepEqual(actual, "file");
+      });
+    });
+    it('can handle no file extension', () => {
+      const filename = removeExtension("file");
+      assert.deepEqual(filename, "file");
+    });
+  });
+  describe('Test of sourceOrBinaryTypeFromFilename()', () => {
+    it('can extract Source file extension', () => {
+      ALL_SOURCE.forEach((ext) => {
+        const filename = `file${ext}`;
+        const actual   = sourceOrBinaryTypeFromFilename(filename);
+        assert.deepEqual(actual, ext);
+      });
+    });
+    it('can extract Binary file extension', () => {
+      ALL_BINARY.forEach((ext) => {
+        const filename = `file${ext}`;
+        const actual   = sourceOrBinaryTypeFromFilename(filename);
+        assert.deepEqual(actual, ext);
+      });
+    });
+    it('returns null for unmatched file extension', () => {
+      const ext = ".cpp";
+      assert.isFalse((Object.values(ALL) as string[]).includes(ext));
+      const filename = `file${ext}`;
+      const actual   = sourceOrBinaryTypeFromFilename(filename);
+      assert.isNull(actual);
+    });
+    it('can extract upper case file extension', () => {
+      const ext          = ALL[0];
+      const upperCaseExt = ext.toUpperCase();
+      const filename     = `file${upperCaseExt}`;
+      const actual       = sourceOrBinaryTypeFromFilename(filename);
+      assert.deepEqual(actual, ext);
+    });
+  });
+  describe('Test of sourceTypeFromFilename()', () => {
+    it('can extract Source file extension', () => {
+      ALL_SOURCE.forEach((ext) => {
+        const filename = `file${ext}`;
+        const actual   = sourceTypeFromFilename(filename);
+        assert.deepEqual(actual, ext);
+      });
+    });
+    it('returns null for a Binary file extension', () => {
+      ALL_BINARY.forEach((ext) => {
+        const filename = `file${ext}`;
+        const actual   = sourceTypeFromFilename(filename);
+        assert.isNull(actual);
+      });
+    });
+    it('returns null for unmatched file extension', () => {
+      const ext = ".cpp";
+      assert.isFalse((Object.values(ALL_SOURCE) as string[]).includes(ext));
+      const filename = `file${ext}`;
+      const actual   = sourceTypeFromFilename(filename);
+      assert.isNull(actual);
+    });
+    it('can extract upper case file extension', () => {
+      const ext          = ALL_SOURCE[0];
+      const upperCaseExt = ext.toUpperCase();
+      const filename     = `file${upperCaseExt}`;
+      const actual       = sourceTypeFromFilename(filename);
+      assert.deepEqual(actual, ext);
+    });
+  });
+  describe('Test of binaryTypeFromFilename()', () => {
+    it('returns null for a Source file extension', () => {
+      ALL_SOURCE.forEach((ext) => {
+        const filename = `file${ext}`;
+        const actual   = binaryTypeFromFilename(filename);
+        assert.isNull(actual);
+      });
+    });
+    it('can extract Binary file extension', () => {
+      ALL_BINARY.forEach((ext) => {
+        const filename = `file${ext}`;
+        const actual   = binaryTypeFromFilename(filename);
+        assert.deepEqual(actual, ext);
+      });
+    });
+    it('returns null for unmatched file extension', () => {
+      const ext = ".cpp";
+      assert.isFalse((Object.values(ALL_BINARY) as string[]).includes(ext));
+      const filename = `file${ext}`;
+      const actual   = binaryTypeFromFilename(filename);
+      assert.isNull(actual);
+    });
+    it('can extract upper case file extension', () => {
+      const ext          = ALL_BINARY[0];
+      const upperCaseExt = ext.toUpperCase();
+      const filename     = `file${upperCaseExt}`;
+      const actual       = binaryTypeFromFilename(filename);
+      assert.deepEqual(actual, ext);
+    });
+  });
+  describe('Test of filenameIs()', () => {
+    it('can identify Source file extension', () => {
+      ALL_SOURCE.forEach((ext) => {
+        const filename = `file${ext}`;
+        const actual   = filenameIs(filename, ext);
+        assert.isTrue(actual);
+      });
+    });
+    it('can identify Binary file extension', () => {
+      ALL_BINARY.forEach((ext) => {
+        const filename = `file${ext}`;
+        if (ext == Binary.Model) { // Special case for .model.js
+          const actual = filenameIs(filename, Binary.WebKeyboard);
+          assert.isFalse(actual);
+        }
+        const actual = filenameIs(filename, ext);
+        assert.isTrue(actual);
+      });
+    });
+    it('can identify upper case file extension', () => {
+      const ext          = ALL[0];
+      const upperCaseExt = ext.toUpperCase();
+      const filename     = `file${upperCaseExt}`;
+      const actual       = filenameIs(filename, ext);
+      assert.isTrue(actual);
+    });
+  });
+  describe('Test of replaceExtension()', () => {
+    it('can replace an extension', () => {
+      const oldExt      = ".cpp";
+      const newExt      = ".js";
+      const oldFilename = `file${oldExt}`;
+      const newFilename = `file${newExt}`;
+      const actual      = replaceExtension(oldFilename, oldExt, newExt);
+      assert.deepEqual(actual, newFilename);
+    });
+    it('should return null for incorrect old extension (too short)', () => {
+      const oldExt      = ".ts";
+      const newExt      = ".js";
+      const oldFilename = `file.c`;
+      const actual      = replaceExtension(oldFilename, oldExt, newExt);
+      assert.isNull(actual);
+    });
+    it('should return null for incorrect old extension (too long)', () => {
+      const oldExt      = ".ts";
+      const newExt      = ".js";
+      const oldFilename = `file.cpp`;
+      const actual      = replaceExtension(oldFilename, oldExt, newExt);
+      assert.isNull(actual);
+    });
+    // it('should return null for null old extension', () => {
+    //   const newExt      = ".js";
+    //   const oldFilename = `file.ts`;
+    //   const actual      = replaceExtension(oldFilename, null, newExt);
+    //   assert.isNull(actual);
+    // });
+    // it('should return null for null new extension', () => {
+    //   const oldExt      = ".ts";
+    //   const oldFilename = `file.ts`;
+    //   const actual      = replaceExtension(oldFilename, oldExt, null);
+    //   assert.isNull(actual);
+    // });
+  });
+});