diff --git a/src/vs/workbench/api/common/extHostTestItem.ts b/src/vs/workbench/api/common/extHostTestItem.ts
index 7807782afd7..35440b3b0fc 100644
--- a/src/vs/workbench/api/common/extHostTestItem.ts
+++ b/src/vs/workbench/api/common/extHostTestItem.ts
@@ -4,11 +4,12 @@
  *--------------------------------------------------------------------------------------------*/
 import * as editorRange from 'vs/editor/common/core/range';
 import { createPrivateApiFor, getPrivateApiFor, IExtHostTestItemApi } from 'vs/workbench/api/common/extHostTestingPrivateApi';
-import { TestIdPathParts } from 'vs/workbench/contrib/testing/common/testId';
+import { TestId, TestIdPathParts } from 'vs/workbench/contrib/testing/common/testId';
 import { createTestItemChildren, ExtHostTestItemEvent, ITestChildrenLike, ITestItemApi, ITestItemChildren, TestItemCollection, TestItemEventOp } from 'vs/workbench/contrib/testing/common/testItemCollection';
-import { ITestItem } from 'vs/workbench/contrib/testing/common/testTypes';
+import { denamespaceTestTag, ITestItem, ITestItemContext } from 'vs/workbench/contrib/testing/common/testTypes';
 import type * as vscode from 'vscode';
 import * as Convert from 'vs/workbench/api/common/extHostTypeConverters';
+import { URI } from 'vs/base/common/uri';
 
 const testItemPropAccessor = <K extends keyof vscode.TestItem>(
 	api: IExtHostTestItemApi,
@@ -83,6 +84,27 @@ const makePropDescriptors = (api: IExtHostTestItemApi, label: string): { [K in k
 	})),
 });
 
+const toItemFromPlain = (item: ITestItem.Serialized): TestItemImpl => {
+	const testId = TestId.fromString(item.extId);
+	const testItem = new TestItemImpl(testId.controllerId, testId.localId, item.label, URI.revive(item.uri) || undefined);
+	testItem.range = Convert.Range.to(item.range || undefined);
+	testItem.description = item.description || undefined;
+	testItem.sortText = item.sortText || undefined;
+	testItem.tags = item.tags.map(t => Convert.TestTag.to({ id: denamespaceTestTag(t).tagId }));
+	return testItem;
+};
+
+export const toItemFromContext = (context: ITestItemContext): TestItemImpl => {
+	let node: TestItemImpl | undefined;
+	for (const test of context.tests) {
+		const next = toItemFromPlain(test.item);
+		getPrivateApiFor(next).parent = node;
+		node = next;
+	}
+
+	return node!;
+};
+
 export class TestItemImpl implements vscode.TestItem {
 	public readonly id!: string;
 	public readonly uri!: vscode.Uri | undefined;
diff --git a/src/vs/workbench/api/common/extHostTesting.ts b/src/vs/workbench/api/common/extHostTesting.ts
index 0fb81ed4046..a7c81eb67d2 100644
--- a/src/vs/workbench/api/common/extHostTesting.ts
+++ b/src/vs/workbench/api/common/extHostTesting.ts
@@ -17,7 +17,7 @@ import { generateUuid } from 'vs/base/common/uuid';
 import { ExtHostTestingShape, ILocationDto, MainContext, MainThreadTestingShape } from 'vs/workbench/api/common/extHost.protocol';
 import { ExtHostCommands } from 'vs/workbench/api/common/extHostCommands';
 import { IExtHostRpcService } from 'vs/workbench/api/common/extHostRpcService';
-import { ExtHostTestItemCollection, TestItemImpl, TestItemRootImpl } from 'vs/workbench/api/common/extHostTestItem';
+import { ExtHostTestItemCollection, TestItemImpl, TestItemRootImpl, toItemFromContext } from 'vs/workbench/api/common/extHostTestItem';
 import * as Convert from 'vs/workbench/api/common/extHostTypeConverters';
 import { TestRunProfileKind, TestRunRequest } from 'vs/workbench/api/common/extHostTypes';
 import { TestId, TestIdPathParts, TestPosition } from 'vs/workbench/contrib/testing/common/testId';
@@ -48,7 +48,7 @@ export class ExtHostTesting implements ExtHostTestingShape {
 
 		commands.registerArgumentProcessor({
 			processArgument: arg =>
-				arg?.$mid === MarshalledId.TestItemContext ? Convert.TestItem.toItemFromContext(arg) : arg,
+				arg?.$mid === MarshalledId.TestItemContext ? toItemFromContext(arg) : arg,
 		});
 	}
 
diff --git a/src/vs/workbench/api/common/extHostTypeConverters.ts b/src/vs/workbench/api/common/extHostTypeConverters.ts
index 9ea7d1585bb..b1874a73422 100644
--- a/src/vs/workbench/api/common/extHostTypeConverters.ts
+++ b/src/vs/workbench/api/common/extHostTypeConverters.ts
@@ -32,7 +32,7 @@ import * as notebooks from 'vs/workbench/contrib/notebook/common/notebookCommon'
 import { ICellRange } from 'vs/workbench/contrib/notebook/common/notebookRange';
 import * as search from 'vs/workbench/contrib/search/common/search';
 import { TestId } from 'vs/workbench/contrib/testing/common/testId';
-import { CoverageDetails, denamespaceTestTag, DetailType, ICoveredCount, IFileCoverage, ISerializedTestResults, ITestErrorMessage, ITestItem, ITestItemContext, ITestTag, namespaceTestTag, TestMessageType, TestResultItem } from 'vs/workbench/contrib/testing/common/testTypes';
+import { CoverageDetails, denamespaceTestTag, DetailType, ICoveredCount, IFileCoverage, ISerializedTestResults, ITestErrorMessage, ITestItem, ITestTag, namespaceTestTag, TestMessageType, TestResultItem } from 'vs/workbench/contrib/testing/common/testTypes';
 import { EditorGroupColumn } from 'vs/workbench/services/editor/common/editorGroupColumn';
 import { ACTIVE_GROUP, SIDE_GROUP } from 'vs/workbench/services/editor/common/editorService';
 import type * as vscode from 'vscode';
@@ -1786,25 +1786,6 @@ export namespace TestItem {
 			sortText: item.sortText || undefined,
 		};
 	}
-
-	export function toItemFromContext(context: ITestItemContext): vscode.TestItem {
-		let node: vscode.TestItem | undefined;
-		for (const test of context.tests) {
-			const next = toPlain(test.item);
-			(node as any).children = {
-				add: () => { },
-				delete: () => { },
-				forEach(fn) { fn(next, this); },
-				get: id => id === test.item.extId ? test.item : undefined,
-				replace: () => { },
-				size: 1,
-			} as vscode.TestItemCollection;
-			(next as any).parent = node;
-			node = next;
-		}
-
-		return node!;
-	}
 }
 
 export namespace TestTag {