When setting up a multi-project scenarios for a CodeRefactoringTest, the invocation location is only allowed in the initial project.

[CyrusNajmabadi]

Example, i tried to setup this config:

            var test = new VerifyCS.Test
            {
                CodeActionIndex = 3,
                TestHost = host,
                TestState =
                {
                    Sources = { text2 },
                    AdditionalProjects =
                    {
                        ["DependencyProject"] =
                        {
                            Sources = { text1 },
                        }
                    },
                    AdditionalProjectReferences = { "DependencyProject" },
                },
                FixedState =
                {
                    Sources = { expected2 },
                    AdditionalProjects =
                    {
                        ["DependencyProject"] =
                        {
                            Sources = { expected1 },
                        }
                    },
                    AdditionalProjectReferences = { "DependencyProject" },
                }
            };
            test.Options.AddRange(PreferImplicitTypeWithInfo());
            await test.RunAsync();

Where the starting location was in text1. This crashed here as the engine was trying to found that location in a tree, but then looked up that tree in the main "TestProject" instance, not teh additional-project instance.

I was able to work around that, but it would be nice to support this.

>    Microsoft.CodeAnalysis.Workspaces.dll!Microsoft.CodeAnalysis.CodeRefactorings.CodeRefactoringContext.CodeRefactoringContext(Microsoft.CodeAnalysis.Document document, Microsoft.CodeAnalysis.Text.TextSpan span, System.Action<Microsoft.CodeAnalysis.CodeActions.CodeAction, Microsoft.CodeAnalysis.Text.TextSpan?> registerRefactoring, bool isBlocking, System.Threading.CancellationToken cancellationToken) Line 60    C#
     Microsoft.CodeAnalysis.Workspaces.dll!Microsoft.CodeAnalysis.CodeRefactorings.CodeRefactoringContext.CodeRefactoringContext(Microsoft.CodeAnalysis.Document document, Microsoft.CodeAnalysis.Text.TextSpan span, System.Action<Microsoft.CodeAnalysis.CodeActions.CodeAction> registerRefactoring, System.Threading.CancellationToken cancellationToken) Line 45    C#
     Microsoft.CodeAnalysis.CodeRefactoring.Testing.dll!Microsoft.CodeAnalysis.Testing.CodeRefactoringTest<Microsoft.CodeAnalysis.Testing.Verifiers.XUnitVerifier>.ApplyRefactoringAsync(Microsoft.CodeAnalysis.Testing.DiagnosticResult triggerSpan, System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.CodeRefactorings.CodeRefactoringProvider> codeRefactoringProviders, int? codeActionIndex, string codeActionEquivalenceKey, System.Action<Microsoft.CodeAnalysis.CodeActions.CodeAction, Microsoft.CodeAnalysis.Testing.IVerifier> codeActionVerifier, Microsoft.CodeAnalysis.Project project, int numberOfIterations, Microsoft.CodeAnalysis.Testing.IVerifier verifier, System.Threading.CancellationToken cancellationToken) Line 218    C#
     Microsoft.CodeAnalysis.CodeRefactoring.Testing.dll!Microsoft.CodeAnalysis.Testing.CodeRefactoringTest<Microsoft.CodeAnalysis.Testing.Verifiers.XUnitVerifier>.VerifyRefactoringAsync(string language, Microsoft.CodeAnalysis.Testing.DiagnosticResult triggerSpan, System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.CodeRefactorings.CodeRefactoringProvider> codeRefactoringProviders, Microsoft.CodeAnalysis.Testing.SolutionState oldState, Microsoft.CodeAnalysis.Testing.SolutionState newState, int numberOfIterations, System.Func<Microsoft.CodeAnalysis.Testing.DiagnosticResult, System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.CodeRefactorings.CodeRefactoringProvider>, int?, string, System.Action<Microsoft.CodeAnalysis.CodeActions.CodeAction, Microsoft.CodeAnalysis.Testing.IVerifier>, Microsoft.CodeAnalysis.Project, int, Microsoft.CodeAnalysis.Testing.IVerifier, System.Threading.CancellationToken, System.Threading.Tasks.Task<(Microsoft.CodeAnalysis.Project project, System.Runtime.ExceptionServices.ExceptionDispatchInfo iterationCountFailure)>> getFixedProject, Microsoft.CodeAnalysis.Testing.IVerifier verifier, System.Threading.CancellationToken cancellationToken) Line 157    C#
     Microsoft.CodeAnalysis.CodeRefactoring.Testing.dll!Microsoft.CodeAnalysis.Testing.CodeRefactoringTest<Microsoft.CodeAnalysis.Testing.Verifiers.XUnitVerifier>.VerifyRefactoringAsync(Microsoft.CodeAnalysis.Testing.SolutionState testState, Microsoft.CodeAnalysis.Testing.SolutionState fixedState, Microsoft.CodeAnalysis.Testing.DiagnosticResult triggerSpan, Microsoft.CodeAnalysis.Testing.IVerifier verifier, System.Threading.CancellationToken cancellationToken) Line 139    C#
     Microsoft.CodeAnalysis.CodeRefactoring.Testing.dll!Microsoft.CodeAnalysis.Testing.CodeRefactoringTest<Microsoft.CodeAnalysis.Testing.Verifiers.XUnitVerifier>.RunAsync(System.Threading.CancellationToken cancellationToken) Line 87    C#

                    var context = new CodeRefactoringContext(project.GetDocument(location.SourceTree), location.SourceSpan, actions.Add, cancellationToken);

Here project.GetDocument is returning null as this is the wrong project instance for that source-tree.