There's a lot of setup code here and quite a bit of duplication from our previous tests. Luckily, you can use what's known as a Test Fixture.

A Test Fixture is simply some code that is run to configure the system under test. For our purposes, create a ContextFixture to set up an InMemory database.

Create a new class named ContextFixture, which is where all the InMemory database creation will happen:

public class ContextFixture : IDisposable
{
  public SpeakerMeetContext Context { get; }

  public ContextFixture()
  {
    var options = new DbContextOptionsBuilder<SpeakerMeetContext>()
        .UseInMemoryDatabase("SpeakerMeetContext")
        .Options;

    Context = new SpeakerMeetContext(options);

    if (!Context.Speakers.Any())
    {
      Context.Speakers.Add(new Speaker {Id = 1, Name = "Test"...});
      Context.SaveChanges();
    }
  }

  public void Dispose()
  {
    Context.Dispose();
  }
}

Now, modify the test class to use the new ContextFixture class:

[Collection("Service")]
[Trait("Category", "Integration")]
public class GetAll : IClassFixture<ContextFixture>
{
  private readonly IRepository<Speaker> _repository;
  private readonly IGravatarService _gravatarService;

  public GetAll(ContextFixture fixture)
  {
    _repository = new Repository<Speaker>(fixture.Context);
    _gravatarService = new GravatarService();
  }

  [Fact]
  public void ItExists()
  {
    var speakerService = new SpeakerService(_repository, _gravatarService);
  }
}

That's quite a bit cleaner. Now, create a new test to ensure a collection of SpeakerSummary objects is returned when the GetAll method of the SpeakerService is called:

[Fact]
public void ItReturnsCollectionOfSpeakerSummary()
{
  // Arrange
  var speakerService = new SpeakerService(_repository, _gravatarService);

  // Act
  var speakers = speakerService.GetAll();

  // Assert
  Assert.NotNull(speakers);
  Assert.IsAssignableFrom<IEnumerable<SpeakerSummary>>(speakers);
}

Next, create a new test class for the Get method of the SpeakerService. The first test should validate that an exception is thrown when a speaker does not exist with the supplied ID:

[Fact]
public void GivenSpeakerNotFoundThenSpeakerNotFoundException()
{
  // Arrange
  var speakerService = new SpeakerService(_repository, _gravatarService);

  // Act
  var exception = Record.Exception(() => speakerService.Get(-1));
 
  // Assert
  Assert.IsAssignableFrom<SpeakerNotFoundException>(exception);
}

You can reuse the ContextFixture that you created earlier:

[Fact]
public void GivenSpeakerFoundThenSpeakerDetailReturned()
{
  // Arrange
  var speakerService = new SpeakerService(_repository, _gravatarService);

  // Act
  var speaker = speakerService.Get(1);

  // Assert
  Assert.NotNull(speaker);
  Assert.IsAssignableFrom<SpeakerDetail>(speaker);
}