Compact Framework and NUnit

I have the idea of a small application I could write for the Windows Mobile. The application will only use its local SQL Server database, at least initially, and it is really simple to create a local database on the device. The only things I need are the physical location of the sdf file on the device and the connection string.

In my "DataBase" class I generate them

private string GetLocalDatabasePath()
{
 string applicationPath = Path.GetDirectoryName(this.GetType().Assembly.GetName().CodeBase);
 string localDatabasePath = applicationPath + Path.DirectorySeparatorChar +
   "TTrack.sdf";
 return localDatabasePath;
}

private string GetLocalConnectionString()
{
 string localConnectionString = "Data Source=" +
   GetLocalDatabasePath();

 return localConnectionString;
}

To create a database I just check if the database file already exists, and if not - I create it. Also, for testing purposes, the delete database function is used.

internal void CreateDatabase()
{
 if (!File.Exists(localDatabasePath))
 {
  using (SqlCeEngine engine = new SqlCeEngine(localConnectionString))
  {
   engine.CreateDatabase();
  }

  RunNonQuery(qryCreateTables);
 }
}

internal void DeleteDatabase()
{
 string dbPath = GetLocalDatabasePath();
 if (File.Exists(dbPath))
 {
  File.Delete(dbPath);
 }
}

The RunNonQuery bit is just the creation of tables in the database.

internal void RunNonQuery(string query)
{
 string connString = GetLocalConnectionString();

 using (SqlCeConnection cn = new SqlCeConnection(connString))
 {
  cn.Open();
  SqlCeCommand cmd = cn.CreateCommand();
  cmd.CommandText = query;
  cmd.ExecuteNonQuery();
 }
}

The query for now just creates the simplest possible "dummy" table

internal string qryCreateTables = "CREATE TABLE Users (" +
 "UserID uniqueidentifier PRIMARY KEY DEFAULT NEWID() NOT NULL, " +
 "Name NVARCHAR(50) NOT NULL )";

The RunScalar, obviously, is used to run ExecuteScalar(). Some refactoring still required to improve the code.

internal int RunScalar(string query)
{
 string connString = GetLocalConnectionString();

 using (SqlCeConnection cn = new SqlCeConnection(connString))
 {
  cn.Open();
  SqlCeCommand cmd = cn.CreateCommand();
  cmd.CommandText = query;
  return int.Parse(cmd.ExecuteScalar().ToString());
 }
}

Now that I can create a database, I can run this simple bit of code to see if it is working.

DataBase db = new DataBase();
 db.CreateDatabase();
 db.RunNonQuery(db.qryInsertRecord);
 MessageBox.Show(db.RunScalar(db.qryCountUsers).ToString());

Database gets created, a record gets inserted, a messagebox with "1" is shown. All is well.

Next, I decide to quickly create and run a simple test for database creation: If the database is present, I delete it, then create a new one, insert one record and test for the count of records indeed being one.

Here is the test I write in NUnit.

[Test]
public void CheckDatabaseCreation()
{
 DataBase db = new DataBase();
 db.SetFileName(@"\Program Files\TestDB\TTrack.sdf");
 db.SetConnectionString(@"Data Source=\Program Files\TestDB\TTrack.sdf");
 db.DeleteDatabase();
 db.CreateDatabase();
 db.RunNonQuery(db.qryInsertRecord);
 int count = db.RunScalar(db.qryCountUsers);
 Assert.AreEqual(count, 1);
}

This does not go as well, however:

What happened there? Oh, of course - the NUnit test runs on the desktop, but the code is supposed to run on the emulator (I don't use the actual device yet). So, it looks like I will have to work on the approach to testing ...

by Evgeny. Also posted on my website