diff --git a/tests/library/test_model_utils.py b/tests/library/test_model_utils.py
new file mode 100644
index 00000000..c432266e
--- /dev/null
+++ b/tests/library/test_model_utils.py
@@ -0,0 +1,137 @@
+import pytest
+import torch
+from library.model_utils import AID
+from torch import nn
+import torch.nn.functional as F
+
+@pytest.fixture
+def input_tensor():
+    # Create a tensor with positive and negative values
+    x = torch.tensor([-2.0, -1.0, 0.0, 1.0, 2.0], requires_grad=True)
+    return x
+
+def test_aid_forward_train_mode(input_tensor):
+    aid = AID(p=0.9)
+    aid.train()
+    
+    # Run several forward passes to test stochastic behavior
+    results = []
+    for _ in range(10):
+        output = aid(input_tensor)
+        results.append(output.detach().clone())
+    
+    # Test that outputs vary (stochastic behavior)
+    all_equal = all(torch.allclose(results[0], results[i]) for i in range(1, 10))
+    assert not all_equal, "All outputs are identical, expected variability in training mode"
+    
+    # Test shape preservation
+    assert results[0].shape == input_tensor.shape
+
+def test_aid_forward_eval_mode(input_tensor):
+    aid = AID(p=0.9)
+    aid.eval()
+    
+    output = aid(input_tensor)
+    
+    # Test deterministic behavior
+    output2 = aid(input_tensor)
+    assert torch.allclose(output, output2), "Expected deterministic behavior in eval mode"
+    
+    # Test correct transformation
+    expected = 0.9 * F.relu(input_tensor) + 0.1 * F.relu(-input_tensor) * -1
+    assert torch.allclose(output, expected), "Incorrect evaluation mode transformation"
+
+def test_aid_gradient_flow(input_tensor):
+    aid = AID(p=0.9)
+    aid.train()
+    
+    # Forward pass
+    output = aid(input_tensor)
+    
+    # Check gradient flow
+    assert output.requires_grad, "Output lost gradient tracking"
+    
+    # Compute loss and backpropagate
+    loss = output.sum()
+    loss.backward()
+    
+    # Verify gradients were computed
+    assert input_tensor.grad is not None, "No gradients were recorded for input tensor"
+    assert torch.any(input_tensor.grad != 0), "Gradients are all zeros"
+
+def test_aid_extreme_p_values():
+    # Test with p=1.0 (only positive values pass through)
+    x = torch.tensor([-2.0, -1.0, 0.0, 1.0, 2.0], requires_grad=True)
+    aid = AID(p=1.0)
+    aid.eval()
+    
+    output = aid(x)
+    expected = torch.tensor([0.0, 0.0, 0.0, 1.0, 2.0])
+    assert torch.allclose(output, expected), "Failed with p=1.0"
+    
+    # Test with p=0.0 (only negative values pass through)
+    x = torch.tensor([-2.0, -1.0, 0.0, 1.0, 2.0], requires_grad=True)
+    aid = AID(p=0.0)
+    aid.eval()
+    
+    output = aid(x)
+    expected = torch.tensor([-2.0, -1.0, 0.0, 0.0, 0.0])
+    assert torch.allclose(output, expected), "Failed with p=0.0"
+
+def test_aid_with_all_positive_values():
+    x = torch.tensor([1.0, 2.0, 3.0, 4.0, 5.0], requires_grad=True)
+    aid = AID(p=0.9)
+    aid.train()
+    
+    # Run forward passes and check that only positive values are affected
+    output = aid(x)
+    
+    # Backprop should work
+    loss = output.sum()
+    loss.backward()
+    assert x.grad is not None, "No gradients were recorded for all-positive input"
+
+def test_aid_with_all_negative_values():
+    x = torch.tensor([-1.0, -2.0, -3.0, -4.0, -5.0], requires_grad=True)
+    aid = AID(p=0.9)
+    aid.train()
+    
+    # Run forward passes and check that only negative values are affected
+    output = aid(x)
+    
+    # Backprop should work
+    loss = output.sum()
+    loss.backward()
+    assert x.grad is not None, "No gradients were recorded for all-negative input"
+
+def test_aid_with_zero_values():
+    x = torch.tensor([0.0, 0.0, 0.0, 0.0, 0.0], requires_grad=True)
+    aid = AID(p=0.9)
+    
+    # Test training mode
+    aid.train()
+    output = aid(x)
+    assert torch.allclose(output, torch.zeros_like(output)), "Expected zeros out for zero input"
+    
+    # Test eval mode
+    aid.eval() 
+    output = aid(x)
+    assert torch.allclose(output, torch.zeros_like(output)), "Expected zeros out for zero input"
+
+def test_aid_integration_with_linear_layer():
+    # Test AID's compatibility with a linear layer
+    linear = nn.Linear(5, 2)
+    aid = AID(p=0.9)
+    
+    model = nn.Sequential(linear, aid)
+    model.train()
+    
+    x = torch.randn(3, 5, requires_grad=True)
+    output = model(x)
+    
+    # Check that gradients flow through the whole model
+    loss = output.sum()
+    loss.backward()
+    
+    assert linear.weight.grad is not None, "No gradients for linear layer weights"
+    assert x.grad is not None, "No gradients for input tensor"