test/Microsoft.TestPlatform.TestUtilities/IntegrationTestBase.cs:1

• workingDirectory! is dereferenced before the null-check, so calling InvokeDotnetTest(..., workingDirectory: null) will throw immediately (even though the following if attempts to guard it). Compute globalJsonPath only after verifying workingDirectory is non-null, or early-return/throw with a clear message when it is null.
  test/Microsoft.TestPlatform.TestUtilities/IntegrationTestBase.cs:1
• The JSON being written is invalid (trailing comma after "vstest", and an extra comma before the closing brace). This will likely cause dotnet test to ignore or error on the file, defeating the intent to enforce the runner. Write valid JSON (no trailing commas and correct brace structure).
  test/Microsoft.TestPlatform.TestUtilities/IntegrationTestBase.cs:1
• Validating global.json by substring match is brittle (formatting/whitespace, different property ordering, or equivalent JSON could fail validation). Prefer parsing JSON and checking test.runner semantically, and consider using Environment.NewLine for message formatting consistency.
  test/Microsoft.TestPlatform.Acceptance.IntegrationTests/SkipIntegrationTestOnNetConditionAttribute.cs:1
• The attribute name and internal field name are confusing relative to behavior: ConditionMode.Include + _include = ...StartsWith(".NET Framework") means “run only on .NET Framework”, not “skip on net”. Consider renaming the attribute to reflect actual behavior (e.g., RunOnlyOnNetFrameworkAttribute) and rename _include to something explicit like _isNetFramework.