Code pollution

1.cs

public class OrderRepository
{
    public void Save(Order order)
    {
        /* ... */
    }

    public Order GetById(long id)
    {
        /* ... */
    }
}

2.cs

[Fact]
public void Some_integration_test()
{
    // Arrange
    var repository = new OrderRepository();
    var service = new OrderService(repository);
    long customerId = 42;

    // Act
    service.DoSomething(customerId);

    // Assert
    // ToDo : check there are 2 orders in the database for the customerId 42
}

3.cs

[Fact]
public void Some_integration_test()
{
    // Arrange
    var repository = new OrderRepository();
    var service = new OrderService(repository);
    long customerId = 42;

    // Act
    service.DoSomething(customerId);

    // Assert
    IReadOnlyList<Order> orders = repository.GetByCustomerId(customerId); // Code added for the use in this unit test
    /* validate orders */
}

4.cs

public class Logger
{
    public void Log(string text)
    {
        /* Log the text */
    }
}

public class Controller
{
    public void SomeMethod(Logger logger)
    {
        logger.Log("SomeMethod is called");
    }
}

5.cs

public class Logger
{
    private readonly bool _isTestEnvironment;

    public Logger(bool isTestEnvironment)
    {
        _isTestEnvironment = isTestEnvironment;
    }

    public void Log(string text)
    {
        if (_isTestEnvironment)
            return;

        /* Log the text */
    }
}

public class Controller
{
    public void SomeMethod(Logger logger)
    {
        logger.Log("SomeMethod is called");
    }
}

6.cs

[Fact]
public void Some_test()
{
    // Arrange
    var logger = new Logger(true);
    var controller = new Controller();

    // Act
    controller.SomeMethod(logger);

    // Assert
    /* ... */
}

7.cs

public interface ILogger
{
    void Log(string text);
}

public class Logger : ILogger
{
    public void Log(string text)
    {
        /* Log the text */
    }
}

public class FakeLogger : ILogger
{
    public void Log(string text)
    {
    }
}

public class Controller
{
    public void SomeMethod(ILogger logger)
    {
        logger.Log("SomeMethod is called");
    }
}

8.cs

[Fact]
public void Some_test()
{
    // Arrange
    ILogger logger = new FakeLogger(); // FakeLogger instead of Logger
    var controller = new Controller();

    // Act
    controller.SomeMethod(logger);

    // Assert
    /* ... */
}