Move test helper to TestAccessor

src/Workspaces/Core/Portable/Workspace/Solution/ProjectDependencyGraph.cs

@@ -241,21 +241,6 @@ private void ComputeTransitiveReferences(ProjectId project, HashSet<ProjectId> r
             }
         }
 
-        /// <summary>
-        /// Gets the list of projects that directly or transitively depend on this project, if it has already been
-        /// cached.
-        /// </summary>
-        internal ImmutableHashSet<ProjectId>? TryGetProjectsThatTransitivelyDependOnThisProject(ProjectId projectId)
-        {
-            if (projectId is null)
-            {
-                throw new ArgumentNullException(nameof(projectId));
-            }
-
-            _reverseTransitiveReferencesMap.TryGetValue(projectId, out var projects);
-            return projects;
-        }
-
         /// <summary>
         /// Gets the list of projects that directly or transitively depend on this project.
         /// </summary>
@@ -427,5 +412,33 @@ private void ComputedDependencySet(ProjectId project, HashSet<ProjectId> result)
                 }
             }
         }
+
+        internal TestAccessor GetTestAccessor()
+            => new TestAccessor(this);
+
+        internal readonly struct TestAccessor
+        {
+            private readonly ProjectDependencyGraph _instance;
+
+            public TestAccessor(ProjectDependencyGraph instance)
+            {
+                _instance = instance;
+            }
+
+            /// <summary>
+            /// Gets the list of projects that directly or transitively depend on this project, if it has already been
+            /// cached.
+            /// </summary>
+            public ImmutableHashSet<ProjectId>? TryGetProjectsThatTransitivelyDependOnThisProject(ProjectId projectId)
+            {
+                if (projectId is null)
+                {
+                    throw new ArgumentNullException(nameof(projectId));
+                }
+
+                _instance._reverseTransitiveReferencesMap.TryGetValue(projectId, out var projects);
+                return projects;
+            }
+        }
     }
 }

src/Workspaces/CoreTest/SolutionTests/ProjectDependencyGraphTests.cs

@@ -513,7 +513,7 @@ public void TestReverseTransitiveReferencesAfterProjectReferenceRemoval_Preserve
             // Before any other operations, verify that TryGetProjectsThatTransitivelyDependOnThisProject returns a
             // non-null set. Specifically, it returns the _same_ set that was computed prior to the project reference
             // removal.
-            Assert.Same(expected, solution.State.GetProjectDependencyGraph().TryGetProjectsThatTransitivelyDependOnThisProject(d.Id));
+            Assert.Same(expected, solution.State.GetProjectDependencyGraph().GetTestAccessor().TryGetProjectsThatTransitivelyDependOnThisProject(d.Id));
         }
 
         [Fact, Trait(Traits.Feature, Traits.Features.Workspace)]
@@ -541,7 +541,7 @@ public void TestReverseTransitiveReferencesAfterProjectReferenceRemoval_Preserve
             // Before any other operations, verify that TryGetProjectsThatTransitivelyDependOnThisProject returns a
             // non-null set. Specifically, it returns the _same_ set that was computed prior to the project reference
             // removal.
-            Assert.Same(expected, solution.State.GetProjectDependencyGraph().TryGetProjectsThatTransitivelyDependOnThisProject(e.Id));
+            Assert.Same(expected, solution.State.GetProjectDependencyGraph().GetTestAccessor().TryGetProjectsThatTransitivelyDependOnThisProject(e.Id));
         }
 
         [Fact, Trait(Traits.Feature, Traits.Features.Workspace)]
@@ -569,7 +569,7 @@ public void TestReverseTransitiveReferencesAfterProjectReferenceRemoval_DiscardI
 
             // Before any other operations, verify that TryGetProjectsThatTransitivelyDependOnThisProject returns a
             // null set.
-            Assert.Null(solution.State.GetProjectDependencyGraph().TryGetProjectsThatTransitivelyDependOnThisProject(c.Id));
+            Assert.Null(solution.State.GetProjectDependencyGraph().GetTestAccessor().TryGetProjectsThatTransitivelyDependOnThisProject(c.Id));
             VerifyReverseTransitiveReferences(solution, "C", new string[] { "B" });
         }