Testcontainers Integration Tests

What it does

When your agent uses it

• Tasks that involve Integration testing

Example prompts

• “/testcontainers-integration-tests”

Requirements

• Docker

Workflow steps

6 steps, taken from the first numbered list in SKILL.md.

1. 1Real Infrastructure Over Mocks - Use actual databases/services in containers, not mocks
2. 2Test Isolation - Each test gets fresh containers or fresh data
3. 3Automatic Cleanup - TestContainers handles container lifecycle and cleanup
4. 4Fast Startup - Reuse containers across tests in the same class when appropriate
5. 5CI/CD Compatible - Works seamlessly in Docker-enabled CI environments
6. 6Port Randomization - Containers use random ports to avoid conflicts

What it can do on your machine

Read from SKILL.md and the folder at commit e426ed9. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  No scripts in the folder and no shell commands in SKILL.md (its code samples are csharp, yaml and xml).

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names these keys or tokens, usually read from environment variables:

  • SA_PASSWORD

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Testcontainers Integration Tests loads about 1.8k tokens when it runs. Until then it costs about 54 tokens; SKILL.md has 388 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~54

When it runs · the whole SKILL.md, loaded when a task matches

~1.8k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from Aaronontheweb/dotnet-skills at commit e426ed9, republished under its MIT licence (© Aaronontheweb). 388 words, ~1,838 tokens.

name

testcontainers-integration-tests

description

Write integration tests using TestContainers for .NET with xUnit. Covers infrastructure testing with real databases, message queues, and caches in Docker containers instead of mocks.

invocable

false

// BAD: Mocking a database
public class OrderRepositoryTests
{
    private readonly Mock<IDbConnection> _mockDb = new();

    [Fact]
    public async Task GetOrder_ReturnsOrder()
    {
        // This doesn't test real SQL behavior, constraints, or performance
        _mockDb.Setup(db => db.QueryAsync<Order>(It.IsAny<string>()))
            .ReturnsAsync(new[] { new Order { Id = 1 } });

        var repo = new OrderRepository(_mockDb.Object);
        var order = await repo.GetOrderAsync(1);

        Assert.NotNull(order);
    }
}

// GOOD: Testing against a real database
public class OrderRepositoryTests : IAsyncLifetime
{
    private readonly TestcontainersContainer _dbContainer;
    private IDbConnection _connection;

    public OrderRepositoryTests()
    {
        _dbContainer = new TestcontainersBuilder<TestcontainersContainer>()
            .WithImage("mcr.microsoft.com/mssql/server:2022-latest")
            .WithEnvironment("ACCEPT_EULA", "Y")
            .WithEnvironment("SA_PASSWORD", "Your_password123")
            .WithPortBinding(1433, true)
            .Build();
    }

    public async Task InitializeAsync()
    {
        await _dbContainer.StartAsync();
        var port = _dbContainer.GetMappedPublicPort(1433);
        var connectionString = $"Server=localhost,{port};Database=TestDb;User Id=sa;Password=Your_password123;TrustServerCertificate=true";
        _connection = new SqlConnection(connectionString);
        await _connection.OpenAsync();
        await RunMigrationsAsync(_connection);
    }

    public async Task DisposeAsync()
    {
        await _connection.DisposeAsync();
        await _dbContainer.DisposeAsync();
    }

    [Fact]
    public async Task GetOrder_WithRealDatabase_ReturnsOrder()
    {
        await _connection.ExecuteAsync(
            "INSERT INTO Orders (Id, CustomerId, Total) VALUES (1, 'CUST1', 100.00)");

        var repo = new OrderRepository(_connection);
        var order = await repo.GetOrderAsync(1);

        Assert.NotNull(order);
        Assert.Equal("CUST1", order.CustomerId);
        Assert.Equal(100.00m, order.Total);
    }
}

<ItemGroup>
  <PackageReference Include="Testcontainers" Version="*" />
  <PackageReference Include="xunit" Version="*" />
  <PackageReference Include="xunit.runner.visualstudio" Version="*" />

  <!-- Database-specific packages -->
  <PackageReference Include="Microsoft.Data.SqlClient" Version="*" />
  <PackageReference Include="Npgsql" Version="*" /> <!-- For PostgreSQL -->
  <PackageReference Include="MySqlConnector" Version="*" /> <!-- For MySQL -->

  <!-- Other infrastructure -->
  <PackageReference Include="StackExchange.Redis" Version="*" /> <!-- For Redis -->
  <PackageReference Include="RabbitMQ.Client" Version="*" /> <!-- For RabbitMQ -->
</ItemGroup>

_container = new TestcontainersBuilder<TestcontainersContainer>()
    .WithImage("postgres:latest")
    .WithWaitStrategy(Wait.ForUnixContainer()
        .UntilPortIsAvailable(5432)
        .WithTimeout(TimeSpan.FromMinutes(2)))
    .Build();

.WithPortBinding(5432, true) // true = assign random public port

public async Task DisposeAsync()
{
    await _connection?.DisposeAsync();
    await _container?.DisposeAsync();
}

# GitHub Actions
runs-on: ubuntu-latest # Has Docker pre-installed

name: Integration Tests

on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v3

    - name: Setup .NET
      uses: actions/setup-dotnet@v3
      with:
        dotnet-version: 9.0.x

    - name: Run Integration Tests
      run: |
        dotnet test tests/YourApp.IntegrationTests \
          --filter Category=Integration \
          --logger trx

    - name: Cleanup Containers
      if: always()
      run: docker container prune -f

© Aaronontheweb, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 2 other files in skills/testcontainers of Aaronontheweb/dotnet-skills.

• SKILL.md
• database-patterns.md
• infrastructure-patterns.md

Open the folder on GitHubat commit e426ed9

Used in 1 other repository

We found 1 copy of this SKILL.md (exact, near-identical or edited) in other folders, from 1 other GitHub owner. This page covers the copy in Aaronontheweb/dotnet-skills, which our catalogue first saw on October 7, 2026.

• NeverSight/learn-skills.devdata/skills-md/aaronontheweb/dotnet-skills/testcontainers-integration-tests