A complete basic sample

Create a console applicaion and instanciate a SqlConnection to your SQL Server database.

All these examples use an EMP employees table:

EMPNO	ENAME	JOB	MGR
7369	SMITH	CLERK	7566
7499	ALLEN	SALESMAN	7566
7521	WARD	SALESMAN	7566
7566	JONES	MANAGER	NULL

public class MyApplication
{
    public static DbConnection MyConnection;

    public static void Main(string[] args)
    {
        MyConnection = new SqlConnection("Server=.;Database=Scott;");
        MyConnection.Open();

        var count = GetNumberOfEmployees();

        MyConnection.Close();
    }

    // Returns the number of employees
    public static int GetNumberOfEmployees()
    {
        using (var cmd = MyConnection.CreateCommand())
        {
            cmd.CommandText = "SELECT COUNT(*) FROM Employees";
            return Convert.ToInt32(cmd.ExecuteScalar());
        }
    }
}
}

Create a Unit Tests project, referencing your application project. And add the NuGet package DbMocker .

[TestClass]
public class MyTests
{
    [TestMethod]
    public void UnitTest1()
    {
        var conn = new MockDbConnection();

        // Use the DBMocker connection instead of your connection
        MyApplication.MyConnection = conn;

        // When a specific SQL command is detected,
        // Don't execute the query to your database engine (SQL Server, Oracle, SQLite, ...),
        // But returns this Table.
        conn.Mocks
            .When(cmd => cmd.CommandText.StartsWith("SELECT COUNT"))
            .ReturnsTable(MockTable.WithColumns("Count")
                                   .AddRow(14));

        // Call your "classic" methods to tests
        int count = MyApplication.GetNumberOfEmployees(conn);

        Assert.AreEqual(14, count);
    }
}

Tips: When you integrate DBMocker into an existing project, the easiest way is to replace your SqlConnection with MockDbConnection. And to execute the unit tests in Debug mode. You will receive an error for each SQL query that will have to be mocked. Step by step, this allows you to create mocks and simulate your data returns.