C#•2w ago

How can I improve my TestContainers with EF tests?

Hi, all: I've been trying to figure out my favorite way to implement test containers with Entity Framework contexts. I was running into an issue where my tests would persist their database changes between each testcase. To remedy this, I created a transactional test scope that rollsback the changes after each testcase. For this implementation, I have three files: 1) TestFactory.cs: Implements an IAsyncLifetime which my test test classes inherit from, e.x. public class GuildSettingsRepositoryTests(TestFactory factory) : IClassFixture<TestFactory>. It contains the PostgreSqlContainer, an IHost, and offers a CreateTransactionalScopeAsync method my testcases call. 2) TransactionalTestScope.cs: Implements an IAsyncLifetime which rolls back transactions at the end of the scope. Exposes GetRequiredService<T> which testcases call to retreive the testable service. 3) GuildSettingsRepositoryTests.cs: Test class with the previously mentioned definition. Here is a sample of a testcase implementation:

    [Fact]
    public async Task GetByGuildIdAsync_WithNonExistentGuildId_ShouldReturnNull()
    {
        await using var scope = await _factory.CreateTransactionalScopeAsync();
        var guildStorage = scope.GetRequiredService<IGuildSettingsStorage>();
        const long nonExistentGuildId = 999999999999999999L;

        var result = await guildStorage.GetByGuildIdAsync(nonExistentGuildId);

        Assert.Null(result);
    }

    [Fact]
    public async Task GetByGuildIdAsync_WithNonExistentGuildId_ShouldReturnNull()
    {
        await using var scope = await _factory.CreateTransactionalScopeAsync();
        var guildStorage = scope.GetRequiredService<IGuildSettingsStorage>();
        const long nonExistentGuildId = 999999999999999999L;

        var result = await guildStorage.GetByGuildIdAsync(nonExistentGuildId);

        Assert.Null(result);
    }

Issue This works, but calling CreateTransactionalScopeAsync and GetRequiredService each testcase seems redundant and, frankly, incorrect. How can I simplify my testcase boilerplate code or prevent my testcase context updates from persisting between tests?

65 Replies

CanyonOP•2w ago

TestFactory.cs

public sealed class TestFactory : IAsyncLifetime
{
    private readonly PostgreSqlContainer _container = new PostgreSqlBuilder()
        .WithImage("postgres:17")
        .WithCleanUp(true)
        .Build();

    public IHost Host { get; private set; } = default!;

    public IServiceProvider Services => Host.Services;

    public async ValueTask InitializeAsync()
    {
        Environment.SetEnvironmentVariable("DOTNET_ENVIRONMENT", "Test");

        await _container.StartAsync();

        Host = WordBotHost.Build(
            args: [],
            configureConfig: cfg =>
            {
                cfg.AddInMemoryCollection(new Dictionary<string, string?>
                {
                    ["ConnectionStrings:DefaultConnection"] = _container.GetConnectionString()
                });
            });

        await Services.EnsureDatabaseCreatedAsync();
    }

    public async ValueTask DisposeAsync()
    {
        if (Host is IAsyncDisposable asyncDisp)
            await asyncDisp.DisposeAsync();
        await _container.DisposeAsync();
    }

    public async Task<TransactionalTestScope> CreateTransactionalScopeAsync(bool autoRollback = true)
    {
        var scope = Services.CreateScope();
        var ctx = scope.ServiceProvider.GetRequiredService<WordBotDbContext>();
        var tx = await ctx.Database.BeginTransactionAsync();
        return new TransactionalTestScope(scope, tx, autoRollback);
    }
}

public sealed class TestFactory : IAsyncLifetime
{
    private readonly PostgreSqlContainer _container = new PostgreSqlBuilder()
        .WithImage("postgres:17")
        .WithCleanUp(true)
        .Build();

    public IHost Host { get; private set; } = default!;

    public IServiceProvider Services => Host.Services;

    public async ValueTask InitializeAsync()
    {
        Environment.SetEnvironmentVariable("DOTNET_ENVIRONMENT", "Test");

        await _container.StartAsync();

        Host = WordBotHost.Build(
            args: [],
            configureConfig: cfg =>
            {
                cfg.AddInMemoryCollection(new Dictionary<string, string?>
                {
                    ["ConnectionStrings:DefaultConnection"] = _container.GetConnectionString()
                });
            });

        await Services.EnsureDatabaseCreatedAsync();
    }

    public async ValueTask DisposeAsync()
    {
        if (Host is IAsyncDisposable asyncDisp)
            await asyncDisp.DisposeAsync();
        await _container.DisposeAsync();
    }

    public async Task<TransactionalTestScope> CreateTransactionalScopeAsync(bool autoRollback = true)
    {
        var scope = Services.CreateScope();
        var ctx = scope.ServiceProvider.GetRequiredService<WordBotDbContext>();
        var tx = await ctx.Database.BeginTransactionAsync();
        return new TransactionalTestScope(scope, tx, autoRollback);
    }
}

TransactionalTestScope.cs

public sealed class TransactionalTestScope(IServiceScope scope, IDbContextTransaction transaction, bool autoRollback) : IAsyncDisposable
{
    private readonly IServiceScope _scope = scope;
    private readonly IDbContextTransaction _transaction = transaction;
    private readonly bool _autoRollback = autoRollback;
    private bool _completed;

    public IServiceProvider Services => _scope.ServiceProvider;

    public T GetRequiredService<T>() where T : notnull => Services.GetRequiredService<T>();

    public async Task CommitAsync()
    {
        await _transaction.CommitAsync();
        _completed = true;
    }

    public async ValueTask DisposeAsync()
    {
        if (!_completed && _autoRollback)
            await _transaction.RollbackAsync();
        await _transaction.DisposeAsync();
        _scope.Dispose();
    }
}

public sealed class TransactionalTestScope(IServiceScope scope, IDbContextTransaction transaction, bool autoRollback) : IAsyncDisposable
{
    private readonly IServiceScope _scope = scope;
    private readonly IDbContextTransaction _transaction = transaction;
    private readonly bool _autoRollback = autoRollback;
    private bool _completed;

    public IServiceProvider Services => _scope.ServiceProvider;

    public T GetRequiredService<T>() where T : notnull => Services.GetRequiredService<T>();

    public async Task CommitAsync()
    {
        await _transaction.CommitAsync();
        _completed = true;
    }

    public async ValueTask DisposeAsync()
    {
        if (!_completed && _autoRollback)
            await _transaction.RollbackAsync();
        await _transaction.DisposeAsync();
        _scope.Dispose();
    }
}

Not sure if the entire GuildSettingsRepositoryTests.cs is needed so I'll cut it for brevity

mg•2w ago

personally, i use Respawn and call ResetAsync() in every test valid part of the arrange stage of arrange, act, assert imo

Unknown User•2w ago

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CanyonOP•2w ago

I was under the impression I had to create my own IAsyncLifetime for setup and teardown of the MSSQL container. I use the transactions to rollback changes made to the database.

Unknown User•2w ago

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CanyonOP•2w ago

Ideally my fixture/container persists through the tests but my database has one instance per test. I don't understand how to get that to work though.

Unknown User•2w ago

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CanyonOP•2w ago

I think I'm not explaining correctly or I have a wrong understanding somewhere. For definitions: TestFactory - my WebApplicationFactory equivalent. I'm under the impression that this gets its own container. PostgreSqlContainer - my database container. I'm under the impression this gets its own container. Ideally this persists through tests because of the overhead ServiceProvider.GetRequiredService<WordBotDbContext>(); - my database context. Ideally this is cleared out every test. I can try something like

public class GuildSettingsRepositoryTests(WebApplicationFactory<Program> factory) : IClassFixture<WebApplicationFactory<Program>>
{
    private readonly IGuildSettingsStorage guildStorage = factory.Services.GetRequiredService<IGuildSettingsStorage>();
...

public class GuildSettingsRepositoryTests(WebApplicationFactory<Program> factory) : IClassFixture<WebApplicationFactory<Program>>
{
    private readonly IGuildSettingsStorage guildStorage = factory.Services.GetRequiredService<IGuildSettingsStorage>();
...

But I'm not sure how to get the PostgreSqlContainer connection string into the context At the end of the day I'm just trying to test my app with TestContainers and Entity Framework, so I'm open to any kind of changes

Unknown User•2w ago

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How can I improve my TestContainers with EF tests?

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