diff --git a/src/core/singletons/tests/locutus.test.ts b/src/core/singletons/tests/locutus.test.ts
new file mode 100644
index 000000000..4433477e4
--- /dev/null
+++ b/src/core/singletons/tests/locutus.test.ts
@@ -0,0 +1,49 @@
+// (C) Copyright 2015 Moodle Pty Ltd.
+//
+// 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 { Locutus } from '@singletons/locutus';
+
+describe('Locutus singleton', () => {
+
+    it('unserializes PHP strings', () => {
+        expect(Locutus.unserialize('a:3:{s:1:"a";i:1;s:1:"b";i:2;s:3:"foo";s:3:"bar";}')).toEqual({
+            a: 1,
+            b: 2,
+            foo: 'bar',
+        });
+
+        expect(Locutus.unserialize(
+            'O:8:"stdClass":3:{s:3:"foo";s:3:"bar";s:5:"lorem";s:5:"ipsum";s:8:"subclass";O:8:"stdClass":1:{s:2:"ok";b:1;}}',
+        )).toEqual({
+            foo: 'bar',
+            lorem: 'ipsum',
+            subclass: {
+                ok: true,
+            },
+        });
+    });
+
+    it('replaces text within a portion of a string', () => {
+        const originalText = 'A sample text.';
+        const newText = 'foo';
+
+        expect(Locutus.substrReplace(originalText, newText, 0)).toEqual(newText);
+        expect(Locutus.substrReplace(originalText, newText, 0, originalText.length)).toEqual(newText);
+        expect(Locutus.substrReplace(originalText, newText, 0, 0)).toEqual(newText + originalText);
+        expect(Locutus.substrReplace(originalText, newText, 9, -1)).toEqual('A sample foo.');
+        expect(Locutus.substrReplace(originalText, newText, -5, -1)).toEqual('A sample foo.');
+        expect(Locutus.substrReplace(originalText, newText, 2, 6)).toEqual('A foo text.');
+    });
+
+});