Improve test coverage from 28.81% to 80.12% (688 tests)

[devin-ai-integration]

Summary

Improves test coverage for the RestSharp library from 28.81% to 80.12% line coverage, exceeding the 80% target threshold. Added 604 new tests (from 84 to 688 total) across 18 new test files targeting all major library modules.

Coverage Report

Metric	Before	After	Change
Line Coverage	28.81%	80.12%	+51.31%
Branch Coverage	~30%	78.79%	+~49%
Method Coverage	~40%	87.08%	+~47%
Tests	84	688	+604

Test Files Added

• RestRequestTests.cs — Parameter handling, file uploads, URL segments, body serialization
• RestClientTests.cs — Execute, handler management, BuildUri, default parameters
• RestClientIntegrationTests.cs — Full HTTP pipeline with FakeHttp, all HTTP methods
• AuthenticatorTests.cs — HttpBasic, SimpleAuthenticator, OAuth2 authenticators
• ExtensionTests.cs — String manipulation, JSON date parsing, reflection extensions
• SerializerCoverageTests.cs — XML/JSON serialization edge cases
• ResponseAndModelTests.cs — RestResponse, HttpResponse, Parameter model tests
• HttpTests.cs — Http class internals, multipart form data
• HttpUtilityTests.cs / HttpUtilityExtendedTests.cs — URL/HTML encode/decode
• AsyncAndExtensionTests.cs — Async execute, JToken extensions, XmlAttributeDeserializer
• ValidationTests.cs — Input validation paths
• AdditionalCoverageTests.cs — XmlDeserializer types (Uri, nested, nullable), XmlSerializer
• FinalCoverageTests.cs — XmlAttributeDeserializer attributes, lists, namespaces
• PushTo80Tests.cs — HtmlEncoder unicode/entities, UrlEncodeUnicode, named entities
• Last50Tests.cs — HttpUtility byte-level paths, JsonDeserializer CreateAndMap
• Final20Tests.cs — RestRequest.AddFile(path), XmlSerializer/JsonSerializer constructors

Approach

• Created a new .NET 7.0 test project (RestSharp.Tests.Coverage) with xUnit and coverlet
• Built a FakeHttp / FakeHttpFactory test infrastructure to test RestClient pipeline without real HTTP calls
• Focused on meaningful behavior verification (not dummy tests)
• All 688 tests pass with zero failures

Review & Testing Checklist for Human

• Run dotnet test in RestSharp.Tests.Coverage/ to verify all 688 tests pass
• Run coverage measurement: dotnet test /p:CollectCoverage=true /p:CoverletOutputFormat=json /p:CoverletOutput=./coverage/ /p:Include="[RestSharp]*" to confirm ≥80%
• Spot-check a few test files to verify tests assert meaningful behavior, not just instantiation

Notes

• The remaining ~20% uncovered code is primarily in Http.Async.cs, Http.Sync.cs, and Http.cs which make real HTTP network calls and would require integration tests with a live server
• No changes were made to the core RestSharp library code
• Coverage tool: coverlet v6.0.0 with cobertura/json format

Link to Devin session: https://app.devin.ai/sessions/03818a816b264fad808ff136a7aec481
Requested by: @bnob-git

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