Things have improved quite a bit since VSTS 2008 beta when I wrote a post on unit testing private methods.
It appears that both public and internal classes, and methods from public to private can be unit tested in a fairly straightforward manner.
To illustrate that, I coded a simple application and highlighted the unit testing of a private method.
Let’s say I want to create a simulation of the Monopoly game.
I create a new solution with two projects to begin with.
In a console application project the startup code could look like this:
const int numberOfPlayers = 3; var game = new MonopolyGame(numberOfPlayers); game.Play();
In a library project the code for the MonopolyGame class could look like this:
internal class MonopolyGame
{
private readonly int numberOfPlayers;
private const int MinimumNumberOfPlayers = 2;
private const int MaximumNumberOfPlayers = 8;
private List<Player> players;
public MonopolyGame(int numberOfPlayers)
{
this.numberOfPlayers = numberOfPlayers;
}
public void Play()
{
if (this.HasRequiredNumberOfPlayers())
{
this.players.ForEach(player => player.TakeTurn());
}
}
protected bool HasRequiredNumberOfPlayers()
{
return numberOfPlayers >= MinimumNumberOfPlayers && numberOfPlayers <= MaximumNumberOfPlayers;
}
}
Then we add a Test project to the solution.
And add a unit test with the Add / Unit Tests… menu option. Not Add / New Test… which would not generate everything we need for us. (This is something to explore: how to do it all manually?)
This adds all the references and the test reference needed. It adds the unit test class and auto-generates some code for us.
This is what the code looks like for the HasRequiredNumberOfPlayers() test method:
/// <summary>
///A test for HasRequiredNumberOfPlayers
///</summary>
[TestMethod()]
[DeploymentItem("MonopolyGameBL.dll")]
public void HasRequiredNumberOfPlayersTest()
{
PrivateObject param0 = null; // TODO: Initialize to an appropriate value
MonopolyGame_Accessor target = new MonopolyGame_Accessor(param0); // TODO: Initialize to an appropriate value
bool expected = false; // TODO: Initialize to an appropriate value
bool actual;
actual = target.HasRequiredNumberOfPlayers();
Assert.AreEqual(expected, actual);
Assert.Inconclusive("Verify the correctness of this test method.");
}
Initializing the way we need to, we get the following code:
/// <summary>
///A test for HasRequiredNumberOfPlayers
///</summary>
[TestMethod()]
[DeploymentItem("MonopolyGameBL.dll")]
public void HasRequiredNumberOfPlayersTest()
{
int numberOfPlayers = 3;
MonopolyGame_Accessor game = new MonopolyGame_Accessor(numberOfPlayers);
bool expected = true;
bool actual;
actual = game.HasRequiredNumberOfPlayers();
Assert.AreEqual(expected, actual);
}
This can be simplified a little bit:
/// <summary>
///A test for HasRequiredNumberOfPlayers
///</summary>
[TestMethod()]
[DeploymentItem("MonopolyGameBL.dll")]
public void HasRequiredNumberOfPlayersTest()
{
int numberOfPlayers = 3;
var game = new MonopolyGame_Accessor(numberOfPlayers);
Assert.IsTrue(game.HasRequiredNumberOfPlayers());
}
Now, what do I do if I want to test another valid value and let’s say a few that are outside the valid range (at least one under and one above)?
I see three options.
Notes:
You can enable specific other assemblies to access your internal types by using the InternalsVisibleToAttribute. For more information, see Friend Assemblies (C# and Visual Basic).
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