review.md

The provided code seems to be a basic example of how to use Testcontainers for integration testing in .NET with PostgreSQL. Here are some observations and suggestions:

Positive Points:

1. Usage of Testcontainers: You're correctly using Testcontainers to run a PostgreSQL container during tests, which is a good practice for ensuring that tests are isolated from the local environment.
2. Test Coverage: The ShouldReturnTwoCustomers test checks if the CustomerService.GetCustomers() method returns the correct number of customers, which is a basic test coverage.

Potential Issues and Improvements:

1. Initialization of Testcontainers:

   • The InitializeAsync method starts the PostgreSQL container but does not wait for it to be fully ready before proceeding. This can lead to tests failing if the database takes too long to start up.
   • Consider adding a check or delay in InitializeAsync to ensure the database is ready.

2. Connection String Management:

   • The connection string is being fetched directly from the Testcontainers instance. Ensure that this approach is safe for production use, as it might expose sensitive information.

3. Error Handling:

   • The test currently does not handle exceptions or errors that could occur during database operations. Adding try-catch blocks can provide more informative error messages and help in debugging issues.

4. Database Schema Management:

   • The CreateCustomersTable method is called on service initialization, which might lead to table creation every time the service is initialized. Consider creating a migration script or using an existing schema setup for tests.

5. Testing Multiple Scenarios:

   • The current test only checks if three customers are returned. It would be beneficial to add more scenarios, such as checking if the correct customer details are returned, handling cases with no customers, etc.

6. Resource Management:

   • Ensure that all resources (e.g., database connections) are properly disposed of after tests to avoid resource leaks.

7. Code Readability and Comments:

   • Adding comments to explain complex parts of the code can improve readability and make it easier for others (or future you) to understand the codebase.

Example Improvements:

Here’s a revised version of CustomerServiceTest.cs with some improvements:

using FluentAssertions;
using System.Threading.Tasks;
using Testcontainers.PostgreSql;

namespace CustomerService.Tests;

public sealed class CustomerServiceTest : IAsyncLifetime
{
    private readonly PostgreSqlContainer _postgres = new PostgreSqlBuilder()
        .WithImage("postgres:15-alpine")
        .Build();

    public async Task InitializeAsync()
    {
        await _postgres.StartAsync();
        // Ensure the database is ready before proceeding
        await WaitForDatabaseReadiness(_postgres.GetConnectionString());
    }

    private async Task WaitForDatabaseReadiness(string connectionString)
    {
        using (var connection = new NpgsqlConnection(connectionString))
        {
            while (true)
            {
                try
                {
                    await connection.OpenAsync();
                    break;
                }
                catch (NpgsqlException)
                {
                    // Wait for a bit before trying again
                    await Task.Delay(500);
                }
            }
        }
    }

    public async Task DisposeAsync()
    {
        await _postgres.StopAsync();
        await _postgres.DisposeAsync();
    }

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

        // When
        customerService.Create(new Customer(1, "George"));
        customerService.Create(new Customer(2, "John"));
        customerService.Create(new Customer(3, "Mary"));
        var customers = await customerService.GetCustomers();

        // Then
        customers.Count().Should().Be(3);
    }
}

Conclusion:

Overall, the code is functional and demonstrates a good starting point for using Testcontainers in .NET. However, there are several areas where improvements can be made to enhance robustness, reliability, and maintainability.