Streamlining Integration Tests in .NET with Testcontainers

Introduction

Integration testing plays a crucial role in ensuring that different parts of an application work together seamlessly. In the .NET ecosystem, Testcontainers offers a robust and convenient way to create and manage disposable test environments, especially when dealing with dependencies like databases, message queues, or any other services.

What are Testcontainers?

Testcontainers is an open-source library that supports creating lightweight, throwaway instances of common databases, Selenium web browsers, or anything else that can run in a Docker container. It’s incredibly useful for integration testing, as it ensures that your tests have a consistent, isolated environment that mimics production systems.

Setting Up Testcontainers in .NET

Prerequisites

Ensure Docker is installed and running on your machine.
A .NET project set up for testing (using xUnit, NUnit, or MSTest).

Installation

Add the Testcontainers NuGet package to your project.

dotnet add package Testcontainers.MsSql
dotnet add package Microsoft.Data.SqlClient
dotnet add package xunit

Configuration

In your test project, configure Testcontainers to launch the specific dependencies (like a SQL Server, RabbitMQ, etc.) required for your tests.

Creating Your First Integration Test

Define a Container

Create a container instance in your test setup. For example, to use a SQL Server container:

private readonly MsSqlContainer _msSqlContainer 
  = new MsSqlBuilder().Build();

Start the Container

Start the container before running your tests.

public Task InitializeAsync() 
  => _msSqlContainer.StartAsync();

Write the Test

Write your integration tests using the container’s connection details. Here’s a simple test that checks database connectivity:

[Fact]
public async Task CanConnectToSqlServerContainer()
{
  await using var conn = new SqlConnection(_msSqlContainer.GetConnectionString());
  await conn.OpenAsync();

  await using var command = conn.CreateCommand();
  command.CommandText = "SELECT 1;";

  var actual = await command.ExecuteScalarAsync() as int?;
  Assert.Equal(1, actual.GetValueOrDefault());
}

Clean Up

Ensure the container is disposed of after tests are completed to avoid resource leaks.

public Task DisposeAsync()
  => _msSqlContainer.DisposeAsync().AsTask();

Conclusion

Testcontainers simplifies the process of writing integration tests in .NET by handling the setup and teardown of your test environments. This not only makes your tests more reliable but also eases the process of maintaining and updating your test suites.

Write Robust Integration Tests with Testcontainers