Character copier

We use this kata to demonstrate the concepts of test doubles.

Overview

The character copier is a simple class that reads characters from a source and copies them to a destination one character at a time.

When the Copy() method is called on the copier, it should read characters from the source and copy them to the destination until the source returns a newline (‘\n’). Implement the character copier using test doubles for the source and the destination as follows.

Start from these definitions:

Copier.cs

public class Copier
{
	public Copier(ISource source, IDestination destination) {}
	public void Copy() {}
}

ISource.cs

public interface ISource
{
	char GetChar();
}

IDestination.cs

public interface IDestination
{
	void SetChar(char character);
}

Objectives

1. Write a stub for source and a spy for destination in your test project.

2. Repeat the kata but use a mocking framework to create mocks for source and destination.

What differences did you find between the two approaches? Which is simpler? What are the pros and cons of each approach?

Examples

Source characters: "abc\n" (string) or {'a', 'b', 'c', '\n'} (array of char)

Copier.Copy();

Destination characters: "abc" (string) or {'a', 'b', 'c'} (array of char)