Open up orchestrator experimentally

[Evangelink]

Fix #5554

[Copilot]

Pull request overview

This PR exposes the test host orchestrator functionality as a public experimental API to enable third-party extensions to implement custom orchestration strategies (e.g., distributing tests across processes/machines or implementing custom retry logic).

Changes:

• Made ITestHostOrchestrator and ITestHostOrchestratorManager public interfaces with experimental attribute
• Created IInternalTestHostOrchestratorManager to retain internal-only members while exposing core functionality publicly
• Added TestHostOrchestrator property to ITestApplicationBuilder as an experimental public API
• Simplified RetryExtensions to use the new public API instead of casting to internal types

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
ITestHostOrchestrator.cs	Made interface public and added XML documentation and experimental attribute
ITestHostOrchestratorManager.cs	Split into public interface with experimental attribute and internal interface for advanced functionality
TestHostOrchestratorManager.cs	Updated to implement the internal interface
ITestHostBuilder.cs	Updated to use internal interface type
TestHostBuilder.cs	Updated to use internal interface type
ITestApplicationBuilder.cs	Added public experimental property for TestHostOrchestrator
TestApplicationBuilder.cs	Implemented public experimental property for TestHostOrchestrator
PublicAPI.Unshipped.txt	Added public API entries for new orchestrator interfaces and property
RetryExtensions.cs	Simplified to use public API instead of internal casting

[Copilot]

Pull request overview

Copilot reviewed 31 out of 31 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 34 out of 34 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 33 out of 33 changed files in this pull request and generated 4 comments.

Comments suppressed due to low confidence (2)

test/UnitTests/Microsoft.Testing.Platform.UnitTests/TestHostOrchestratorManagerTests.cs:1

• These assertions use string.Contains(...) without specifying comparison rules, which can make failures harder to reason about across cultures/casing and reduces clarity. Prefer using the Contains(string, StringComparison) overload (e.g., ordinal) and/or split this into two assertions so failures report which expected substring is missing.
  test/UnitTests/Microsoft.Testing.Platform.UnitTests/TestHostOrchestratorManagerTests.cs:1
• These assertions use string.Contains(...) without specifying comparison rules, which can make failures harder to reason about across cultures/casing and reduces clarity. Prefer using the Contains(string, StringComparison) overload (e.g., ordinal) and/or split this into two assertions so failures report which expected substring is missing.

[Copilot]

Pull request overview

Copilot reviewed 33 out of 33 changed files in this pull request and generated 15 comments.

[Copilot]

Pull request overview

Copilot reviewed 34 out of 34 changed files in this pull request and generated 1 comment.