diff --git a/examples/threads/threads.txs b/examples/threads/threads.txs
index 7396bb40..34286a5d 100644
--- a/examples/threads/threads.txs
+++ b/examples/threads/threads.txs
@@ -6,12 +6,12 @@ spawn_fn = thread["spawn"]
 join_fn = thread["join"]
 
 do task_a()
-    time.sleep(100)
+    time.sleep(200)
     say "Task A completed on worker thread."
 end
 
 do task_b()
-    time.sleep(50)
+    time.sleep(10)
     say "Task B completed on worker thread."
 end
 
diff --git a/stdlib/src/testing.rs b/stdlib/src/testing.rs
index 1c180934..4162517d 100644
--- a/stdlib/src/testing.rs
+++ b/stdlib/src/testing.rs
@@ -160,3 +160,143 @@ impl StdlibRegistry {
         );
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use techscript_runtime::RuntimeConfig;
+
+    #[test]
+    fn test_register_testing() {
+        let mut registry = StdlibRegistry {
+            modules: HashMap::new(),
+        };
+        registry.register_testing();
+
+        assert!(registry.has_module("std.testing"));
+        let module = registry.get_module("std.testing").unwrap();
+        assert_eq!(module.name, "std.testing");
+        assert_eq!(module.version, "1.0.0");
+        assert_eq!(module.exports.len(), 6);
+        assert!(module.exports.contains_key("assert"));
+        assert!(module.exports.contains_key("assert_eq"));
+        assert!(module.exports.contains_key("assert_ne"));
+        assert!(module.exports.contains_key("mock_fn"));
+        assert!(module.exports.contains_key("mock_object"));
+        assert!(module.exports.contains_key("benchmark"));
+    }
+
+    #[test]
+    fn test_testing_functions() {
+        let mut registry = StdlibRegistry {
+            modules: HashMap::new(),
+        };
+        registry.register_testing();
+        let module = registry.get_module("std.testing").unwrap();
+        let mut ctx = RuntimeContext::new(RuntimeConfig::default());
+
+        // assert
+        let assert_fn = module.exports.get("assert").unwrap();
+        assert_eq!(assert_fn.arity(), 2);
+        assert!(assert_fn
+            .call(
+                &mut ctx,
+                vec![
+                    RuntimeValue::Bool(true),
+                    RuntimeValue::Str("ok".to_string())
+                ]
+            )
+            .is_ok());
+        assert!(assert_fn
+            .call(
+                &mut ctx,
+                vec![
+                    RuntimeValue::Bool(false),
+                    RuntimeValue::Str("failed".to_string())
+                ]
+            )
+            .is_err());
+
+        // assert_eq
+        let assert_eq_fn = module.exports.get("assert_eq").unwrap();
+        assert_eq!(assert_eq_fn.arity(), 3);
+        assert!(assert_eq_fn
+            .call(
+                &mut ctx,
+                vec![
+                    RuntimeValue::Int(42),
+                    RuntimeValue::Int(42),
+                    RuntimeValue::Str("numbers match".to_string())
+                ]
+            )
+            .is_ok());
+        assert!(assert_eq_fn
+            .call(
+                &mut ctx,
+                vec![
+                    RuntimeValue::Int(42),
+                    RuntimeValue::Int(100),
+                    RuntimeValue::Str("numbers differ".to_string())
+                ]
+            )
+            .is_err());
+
+        // assert_ne
+        let assert_ne_fn = module.exports.get("assert_ne").unwrap();
+        assert_eq!(assert_ne_fn.arity(), 3);
+        assert!(assert_ne_fn
+            .call(
+                &mut ctx,
+                vec![
+                    RuntimeValue::Int(42),
+                    RuntimeValue::Int(100),
+                    RuntimeValue::Str("numbers differ".to_string())
+                ]
+            )
+            .is_ok());
+        assert!(assert_ne_fn
+            .call(
+                &mut ctx,
+                vec![
+                    RuntimeValue::Int(42),
+                    RuntimeValue::Int(42),
+                    RuntimeValue::Str("numbers match".to_string())
+                ]
+            )
+            .is_err());
+
+        // mock_fn
+        let mock_fn = module.exports.get("mock_fn").unwrap();
+        assert_eq!(mock_fn.arity(), 1);
+        let mock_res = mock_fn
+            .call(&mut ctx, vec![RuntimeValue::Int(123)])
+            .unwrap();
+        if let RuntimeValue::Function(func) = mock_res {
+            let res = func.call(&mut ctx, vec![]).unwrap();
+            assert_eq!(res, RuntimeValue::Int(123));
+        } else {
+            panic!("Expected RuntimeValue::Function");
+        }
+
+        // mock_object
+        let mock_obj_fn = module.exports.get("mock_object").unwrap();
+        assert_eq!(mock_obj_fn.arity(), 1);
+        let obj_res = mock_obj_fn
+            .call(&mut ctx, vec![RuntimeValue::Str("test_obj".to_string())])
+            .unwrap();
+        assert_eq!(obj_res, RuntimeValue::Str("test_obj".to_string()));
+
+        // benchmark
+        let bench_fn = module.exports.get("benchmark").unwrap();
+        assert_eq!(bench_fn.arity(), 2);
+        let mock_res = mock_fn.call(&mut ctx, vec![RuntimeValue::Null]).unwrap();
+        let bench_res = bench_fn
+            .call(&mut ctx, vec![mock_res, RuntimeValue::Int(5)])
+            .unwrap();
+        if let RuntimeValue::Float(elapsed) = bench_res {
+            assert!(elapsed >= 0.0);
+        } else {
+            panic!("Expected RuntimeValue::Float");
+        }
+    }
+}