API_Integration-Testing

Definitions

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# Integration Testing APIs

Integration testing is a form of automated testing.

• For the network
• Server has to run actively
• heavy-weighter than unit tests

Contrary to unit tests (testing: methods, classes - completed), we don’t test a single code unit (such as classes) independent from other units, but we test the interaction of multiple units and how well they integrate.

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# When to use integration tests

The opinions when to use integration testing and when to use unit testing differ a bit depending who you ask.

Most of the time it is stated, that you should use integration tests and unit tests together to have the best test coverage.

# Example Usage: Integration Test

Image you built a webshop - so you have to make sure, that the payment works

• else you would not get any money

Your shopping-cart method you would test with unit tests

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# Using Integration tests for APIs

When doing integration tests with APIs we typically want to test the complete data flow including a HTTP Request, all the logic that happens on the server and the response.

We therefore need a way of accessing the service while it is running from the integration test.

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# How To

1. We assume that there is an existing WebApi or MinimalApi project in your C# Solution.
2. Create a new unit test project.
3. Install the NuGet Package Microsoft.AspNetCore.Mvc.Testing in the unit test project.

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# How To (2)

4. Inside your unit test classes you can use an instance of a HttpClient to access the API.

private readonly HttpClient _client = 
// <Programm> is class-Progamm
	new WebApplicationFactory<Program>().CreateClient();

• WebApplicationFactory is a type imported from the NuGet Package Microsoft.AspNetCore.Mvc.Testing.
  • imitates a running server - does’t have to be started
  • we don’t have to care about the server and where the programm is hosted
• Program references the class Program in your WebApi or MinimalApi project. It therefore needs to be publicly available, so the unit test project can reference it.

public class Program
{
    public static void Main(string[] args)
    {
        var builder = WebApplication.CreateBuilder(args);
        var app = builder.Build();
 
        MyEndpoints.Map(app);
 
        app.Run();
    }
}

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# How To (3)

5. A simple integration test might look like this:

[Test]  
public async Task GetCharacters_IsSuccessful()  
{  
	var response = await _client.GetAsync("/sw-characters");  
	Assert.DoesNotThrow(() => 
		response.EnsureSuccessStatusCode());  
}