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World Congress 2021 • Jun 28, 2021

Using code generation for test automation – the fancy way

Roman Alexis Anastasini

Stop wasting hours on brittle unit tests. Learn how auto-generating C# HTTP clients from OpenAPI specs creates lightning-fast, robust API tests with zero boilerplate.

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#1 about 4 min

Replacing Swashbuckle with NSwag for API testing

Swapping Swashbuckle for NSwag documentation streamlines the initial setup process for generating API clients.

#2 about 3 min

Generating a Swagger JSON file during the build process

Configuring the project file automatically generates an OpenAPI specification immediately after the build process completes.

#3 about 3 min

Creating and configuring the unit test project

Adding an xUnit test project and referencing Microsoft MVC packages prepares the environment for automated testing.

#4 about 2 min

Generating a C# API client from the Swagger JSON

Automating C# client generation during the build phase seamlessly provides typed API endpoints to the test project.

#5 about 4 min

Writing API-level HTTP tests instead of unit tests

Replacing cumbersome unit tests with API-level tests using generated HTTP clients significantly broadens functional test coverage.

#6 about 1 min

Handling API endpoint changes safely with generated clients

Automatically generated clients provide compile-time safety by instantly flagging any renamed or modified HTTP endpoints.

#7 about 6 min

Validating requests and responses using data transfer objects

Leveraging generated data transfer objects enables built-in model validation and straightforward serialization inside test setups.

#8 about 3 min

Testing edge cases and validation errors with API exceptions

Asserting against automatically thrown API exceptions provides a reliable way to verify bad requests and validation errors.

#9 about 4 min

Achieving high test coverage efficiently with API tests

Utilizing automated API integration checks allows teams to efficiently reach minimum statement coverage thresholds.

#10 about 3 min

Creating precise controller code for accurate client generation

Writing explicit controller configurations ensures accurate OpenAPI specifications and reliable client generation.

#11 about 1 min

Switching from Docker databases to in-memory databases

Moving from resource-heavy Docker containers to in-memory databases dramatically reduces test execution times.

#12 about 3 min

Understanding unit testing overhead and code coverage metrics

Maintaining granular unit tests consumes excessive resources compared to using broad API-level integration checks.

#13 about 3 min

Detecting breaking API changes in CI pipelines

Running integration tests with older generated clients helps prevent accidental backward compatibility breaks in CI pipelines.

#14 about 2 min

Managing test state and setup dependencies

Utilizing web application factories and abstract base classes cleanly handles state initialization for individual test classes.

#15 about 2 min

Mocking external service dependencies in API tests

Abstracting external dependencies behind mocked interfaces isolates API tests while preserving full coverage during integration runs.

#16 about 3 min

Unexpected test automation benefits and execution speed improvements

Reusing API clients intended for external consumers significantly reduces test code verbosity and improves overall productivity.

Matching moments

1:25 min

Testing API endpoints visually using Swagger UI

Alex Soto Alex Soto · WWC 2022

1:16 min

Automating documentation and code generation with OpenAPI standards

James Seconde · WWC 2023

7:44 min

Bootstrapping a test-driven asp.net web api

Alex Banul · LIVE

3:18 min

Implementing contract-first API design with OpenAPI and SwaggerHub

Christoph Ruggenthaler · LIVE

1:58 min

Implementing automated API and workflow testing pipelines

David Tielke David Tielke · WWC Europe 2026

3:50 min

Applying test-driven principles to APIs

Sascha Depold +1 · WWC 2021

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