Unit testing when Database is involved - unit-testing

Question

I'm quite new to unit testing and I need an hand to understand if I'm doing things in the correct way. My major problem is regarding the DB testing... Here's my code then I'll expose my perplexities
Consider this class that's an item of a pipeline I've to perform
public class RetrieveApplicationUsernamePipelineStep : IPipelineStep
{
public const string RetrieveApplicationUsernameKey = "RetrieveApplicationUsername";
private readonly IRetrieveApplicationUserRepository repository;
public int Order => 3;
public string Name => RetrieveApplicationUsernameKey;
public RetrieveApplicationUsernamePipelineStep(IRetrieveApplicationUserRepository repository)
{
this.repository = repository;
}
public async Task<IDictionary<string, object>> Action(IDictionary<string, object> context)
{
string res = await repository.GetApplicationUser(context);
context[Resources.ApplicationUser] = res;
return context;
}
}
I wrote the following tests
[TestFixture]
public class RetrieveApplicationUsernamePipelineStepTests
{
private IRetrieveApplicationUserRepository retrieveApplicationUserRepository;
[OneTimeSetUp]
public void Start()
{
var configuration = new ConfigurationFromConfigFile();
retrieveApplicationUserRepository = new RetrieveApplicationUserRepository(configuration);
}
[Test]
public async Task ActionSuccessfullyCompleted()
{
var context = new Dictionary<string, object>();
var repository = Substitute.For<IRetrieveApplicationUserRepository>();
repository.GetApplicationUser(context).Returns("user1");
var pipeline = new RetrieveApplicationUsernamePipelineStep(repository);
var res = await pipeline.Action(context);
Assert.IsNotNull(res[Resources.ApplicationUser]);
Assert.IsNotEmpty((string)res[Resources.ApplicationUser]);
}
[Test]
public void ActionFailingCompleted()
{
var context = new Dictionary<string, object>();
var repository = Substitute.For<IRetrieveApplicationUserRepository>();
repository.GetApplicationUser(context).Throws(new UserMappingNotFoundException());
var pipeline = new RetrieveApplicationUsernamePipelineStep(repository);
Assert.ThrowsAsync<UserMappingNotFoundException>(async () => await pipeline.Action(context));
}
[Test]
public void NameTest()
{
var pipeline = new RetrieveApplicationUsernamePipelineStep(retrieveApplicationUserRepository);
Assert.IsTrue(pipeline.Name == RetrieveApplicationUsernamePipelineStep.RetrieveApplicationUsernameKey);
}
[Test]
public void OrderTest()
{
var pipeline = new RetrieveApplicationUsernamePipelineStep(retrieveApplicationUserRepository);
Assert.IsTrue(pipeline.Order == 3);
}
}
And those test works fine since for ActionSuccessfullyCompleted and ActionFailingCompleted I substitute the IRetrieveApplicationUserRepository's result with my expected one.
The real implementation of ther repository is
public class RetrieveApplicationUserRepository : IRetrieveApplicationUserRepository
{
#region Variables
private readonly IConfiguration configuration;
#endregion
#region Ctor
public RetrieveApplicationUserRepository(IConfiguration configuration)
{
this.configuration = configuration;
}
#endregion
#region IRetrieveApplicationUserRepository
public async Task<string> GetApplicationUser(IDictionary<string, object> context)
{
if (configuration.AppSettings[Resources.ApplicationUserFromDomainUserKey] == null)
throw new KeyNotFoundException(Resources.ApplicationUserFromDomainUserKey);
if (string.IsNullOrEmpty(configuration.ConnectionString))
throw new NullReferenceException();
string storedProcedure = configuration.AppSettings.Get(Resources.ApplicationUserFromDomainUserKey);
string result;
using (var sqlConnection = new SqlConnection(configuration.ConnectionString))
{
using (var sqlCommand = new SqlCommand(storedProcedure, sqlConnection))
{
sqlCommand.CommandType = CommandType.StoredProcedure;
sqlCommand.Parameters.AddWithValue("#DOMAINUSER", context[Resources.DomainUser]);
sqlCommand.Parameters.AddWithValue("#DOMAIN", context[Resources.DomainName]);
sqlCommand.Parameters.AddWithValue("#APPID", context[Resources.ApplicationId]);
sqlConnection.Open();
result = (string)await sqlCommand.ExecuteScalarAsync();
}
}
if (result == null)
throw new UserMappingNotFoundException();
return result;
}
#endregion
}
Here're the questions :
Are the test I wrote correct?
I've seen using Resharper's Code Coverage that it wants me to test-cover the properties...is there a way I can avoid this? is this test meaningful?
What's your approach when you've to unit test component that're related to DB? Have you got a real-db that's used for test? Consider that the real DB is about 10Gb so I don't want to have a copy as mdf (condider I can have this) just to test a small portion of the DB
Talking with my colleagues they told me to use test just for TDD while I wish to use them to avoid regressions
Going back to the DB question, I don't want to have a test where I write if username is "John" and maybe tomorrow John user won't be present in the DB anymore,so that the test I expect to pass wont' pass anoymore

Answer 1

The usual approach is to isolate the database side with an abstraction, so you can provide a test dummy (mock, fake, etc) of that abstraction. Only test an actual database when you do the integration testing.
For the tests of database stored procedures, you may well want a different test harness, creating a new test database in memory (equivalently, in a RAM-backed filesystem). You only need to populate enough data for the individual test (we're doing functional testing here, not performance testing), and you may be able to retain table structure across tests with judicious use of rollback.
I have done this, but it's some time ago, so I'll refrain from giving examples that may be no longer state-of-the-art (even if the code does still exist, and if I could find it).