Create draft proposal for running dotnet test using Microsoft.Testing.Platform

docs/RFCs/011-Sdk-Testing-Platform.md

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+# RFC 011 - Run dotnet test with Microsoft.Testing.Platform
+
+- [x] Approved in principle
+- [x] Under discussion
+- [ ] Implementation
+- [ ] Shipped
+
+## Current State
+
+Currently, when we run `dotnet test` in CLI, we use vstest as a test runner/driver to run tests in test projects.
+
+## Motivation
+
+With `dotnet test`, users should be able to use [Microsoft testing platform](https://learn.microsoft.com/en-us/dotnet/core/testing/unit-testing-platform-intro?tabs=dotnetcli#microsofttestingplatform-pillars) to run their tests for the sake of improving their experience. They should have the option to opt-in/out this new experience.
+
+The reason for opting-in/out this experience is 
+1. if we were to auto-infer if test projects were using vstest or the testing platform is we will end up with many vulnerabilities, thus making it hard to handle this correctly.
+2. Mixed mode (i.e. having projects using vstest and testing platform in the same solution) will never work as the two platforms have different command line options and different features, thus the mapping will not work as expected.
+
+## Note
+
+We want to design in a way we won't break users and it should be backwards compatible.
+
+### Proposed solution
+
+Make this option configurable in global.json.
+
+Here are some global.json samples:
+
+1.
+
+```json
+{
+"testSdk" :
+  {
+    "useTestingPlatform": true
+  }
+}
+```
+
+What if we want to support another test runner?
+
+We simply can't, with this approach we either use the testing platform, or fallback to vstest if this property was set to false.
+
+2.
+
+```json
+{
+"testSdk" :
+  {
+    "testRunner": "vstest/testingplatform"
+  }
+}
+```
+
+What if we decide to extract the testing platform as an external tool?
+
+We still could support more options.
+
+But if, for some reason, the latest version was broken, we will break as well.
+
+3.
+
+```json
+{
+"testSdk" :
+  {
+    "testRunner": "vstest/testingplatform/...",
+    "version": "1.5.0"
+  }
+}
+```
+
+Users are allowed to force install a specific version of the tool.
+
+If not specified then we will fallback to the latest version.
+
+### Default
+
+- If no test runner was provided in global.json, the default is set to vstest.
+
+## Unresolved questions
+
+None.