test-extensions

name	test-extensions
description	Testing utilities for .NET — WireMock server setup from OpenAPI specifications using AT.Common.TestExtensions. Use this skill when writing integration or contract tests that mock HTTP dependencies using an OpenAPI spec.
license	MIT
metadata	{"domain":"testing","tags":"testing wiremock openapi mocking dotnet integration-tests contract-tests"}

TestExtensions Skill — Arbeidstilsynet/dotnet-common

Arbeidstilsynet.Common.TestExtensions (AT.Common.TestExtensions.Publish) provides testing helpers, primarily for setting up WireMock servers from OpenAPI specifications.

---

Installation

dotnet add package Arbeidstilsynet.Common.TestExtensions

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WireMock + OpenAPI (AddOpenApiMappings)

Automatically generate WireMock stub mappings from an OpenAPI spec. Example responses are generated from the schema definitions.

Basic usage

using WireMock.Server;
using Arbeidstilsynet.Common.TestExtensions.Extensions;

var server = WireMockServer.Start();

using var fileStream = File.Open(
    "path/to/your/openapi.json",
    FileMode.Open,
    FileAccess.Read
);

server.AddOpenApiMappings(fileStream);

Custom mapping visitor

Transform generated mappings before they are registered (e.g. override response bodies or status codes):

server.AddOpenApiMappings(
    openApiSpecStream: fileStream,
    mappingVisitor: mapping =>
    {
        // Override a specific endpoint's response
        if (mapping.Request?.Path?.Matchers?.Any(m => m.Pattern?.ToString()?.Contains("/my-endpoint") == true) == true)
        {
            mapping.Response.Body = """{"id": "overridden-id"}""";
        }
        return mapping;
    }
);

Custom parser settings

using WireMock.Net.OpenApiParser.Settings;

server.AddOpenApiMappings(
    openApiSpecStream: fileStream,
    parserSettings: new WireMockOpenApiParserSettings
    {
        ExampleValues = new WireMockOpenApiParserExampleValues(),
    }
);

---

Generated Example Values

By default, AddOpenApiMappings uses a fixed DateTime.UtcNow snapshot for all date/datetime example values. This ensures deterministic responses within a single test run.

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WireMockExtensions.AddOpenApiMappings Signature

public static void AddOpenApiMappings(
    this WireMockServer server,
    Stream openApiSpecStream,
    Func<MappingModel, MappingModel>? mappingVisitor = null,
    WireMockOpenApiParserSettings? parserSettings = null
)

---

Limitations

• Endpoints that return oneOf in the response schema will not have stubs generated for them.
• The OpenAPI spec must be provided as a JSON stream.

---

Typical Integration Test Setup

public class MyServiceTests : IDisposable
{
    private readonly WireMockServer _server;

    public MyServiceTests()
    {
        _server = WireMockServer.Start();

        using var stream = File.OpenRead("Fixtures/external-api.openapi.json");
        _server.AddOpenApiMappings(stream);
    }

    [Fact]
    public async Task GetData_ReturnsExpectedResponse()
    {
        // Configure your HTTP client to point to _server.Urls[0]
        // Act and Assert
    }

    public void Dispose() => _server.Stop();
}

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Adding TestExtensions — Checklist

1. dotnet add package Arbeidstilsynet.Common.TestExtensions
2. Place the OpenAPI spec JSON in a Fixtures/ folder of your test project
3. Mark the spec file as <CopyToOutputDirectory>Always</CopyToOutputDirectory> in the .csproj
4. Call server.AddOpenApiMappings(stream) in test setup
5. Point your HttpClient base address to server.Urls[0]
6. Use mappingVisitor to override specific responses that need non-default values