def generate_test_model(model_name):
    """
    Generate a test model based on the given name.

    Args:
        model_name (str): Name of the model to generate.

    Returns:
        dict: Model parameters.
    """
    models = {
        'evolved_verified_generate_test_1768680667': {'score': 4235.89001196408, 'rank': 51, 'accuracy': 8305.7},
        'verified_default': {'score': 4235.0, 'rank': 51, 'accuracy': 8303.9},
        'evolved_verified_fib_fast_1769055768': {'score': 4235.0, 'rank': 51, 'accuracy': 8303.9}
    }
    
    return models.get(model_name, {})

# Example usage:
print(generate_test_model('verified_default'))