docker-docs/content/guides/testcontainers-dotnet-getting-started/write-tests.md

title, linkTitle, description, weight

title	linkTitle	description	weight
Write tests with Testcontainers	Write tests	Write integration tests using Testcontainers for .NET and xUnit with a real PostgreSQL database.	20

Add Testcontainers dependencies

Add the Testcontainers PostgreSQL module to the test project:

$ dotnet add ./CustomerService.Tests/CustomerService.Tests.csproj package Testcontainers.PostgreSql

Write the test

Create CustomerServiceTest.cs in the test project:

using Testcontainers.PostgreSql;

namespace Customers.Tests;

public sealed class CustomerServiceTest : IAsyncLifetime
{
    private readonly PostgreSqlContainer _postgres = new PostgreSqlBuilder()
        .WithImage("postgres:16-alpine")
        .Build();

    public Task InitializeAsync()
    {
        return _postgres.StartAsync();
    }

    public Task DisposeAsync()
    {
        return _postgres.DisposeAsync().AsTask();
    }

    [Fact]
    public void ShouldReturnTwoCustomers()
    {
        // Given
        var customerService = new CustomerService(new DbConnectionProvider(_postgres.GetConnectionString()));

        // When
        customerService.Create(new Customer(1, "George"));
        customerService.Create(new Customer(2, "John"));
        var customers = customerService.GetCustomers();

        // Then
        Assert.Equal(2, customers.Count());
    }
}

Here's what the test does:

• Declares a PostgreSqlContainer using the PostgreSqlBuilder with the postgres:16-alpine Docker image.
• Implements IAsyncLifetime for container lifecycle management:
  • InitializeAsync() starts the container before the test runs.
  • DisposeAsync() stops and removes the container after the test finishes.
• ShouldReturnTwoCustomers() creates a CustomerService with connection details from the container, inserts two customers, fetches all customers, and asserts the count.