Test documentation formatting and typing

Pin the Razor output for indentation, tabs, inline XML and malformed input in both file kinds. These tests exercise Razor's formatting and typing pipeline without separately testing Roslyn.

Author: davidwengier

src/Razor/src/Razor/test/Microsoft.CodeAnalysis.Razor.CohostingShared.UnitTests/Endpoints/CohostOnAutoInsertEndpointTest.cs

@@ -505,6 +505,57 @@ void TestMethod() {}
             triggerCharacter: "\n");
     }
 
+    [Theory, CombinatorialData]
+    [WorkItem("https://github.com/dotnet/roslyn/issues/85414")]
+    public async Task DocumentationDirective_OnEnterAfterOpenBrace(bool isComponent)
+    {
+        await VerifyOnAutoInsertAsync(
+            input: """
+                @documentation {
+                    $$
+                }
+                """,
+            output: null,
+            triggerCharacter: "\n",
+            fileKind: isComponent ? RazorFileKind.Component : RazorFileKind.Legacy);
+    }
+
+    [Theory, CombinatorialData]
+    [WorkItem("https://github.com/dotnet/roslyn/issues/85414")]
+    public async Task DocumentationDirective_OnEnterInBody(
+        bool isComponent,
+        [CombinatorialValues("This is some text", "* A bullet point", "/// Literal slashes")] string text)
+    {
+        await VerifyOnAutoInsertAsync(
+            input: $$"""
+                @documentation {
+                    <summary>
+                    {{text}}
+                    $$
+                    </summary>
+                }
+                """,
+            output: null,
+            triggerCharacter: "\n",
+            fileKind: isComponent ? RazorFileKind.Component : RazorFileKind.Legacy);
+    }
+
+    [Theory, CombinatorialData]
+    [WorkItem("https://github.com/dotnet/roslyn/issues/85414")]
+    public async Task DocumentationDirective_OnEnterAfterXmlElement(bool isComponent)
+    {
+        await VerifyOnAutoInsertAsync(
+            input: """
+                @documentation {
+                    <summary>Some documentation</summary>
+                    $$
+                }
+                """,
+            output: null,
+            triggerCharacter: "\n",
+            fileKind: isComponent ? RazorFileKind.Component : RazorFileKind.Legacy);
+    }
+
     [Fact]
     public async Task DoNotAutoInsertCSharp_OnForwardSlashWithFormatOnTypeDisabled()
     {