diff --git a/src/test/datascience/dataScienceIocContainer.ts b/src/test/datascience/dataScienceIocContainer.ts
index bbf3f680b093..04c71fe303ab 100644
--- a/src/test/datascience/dataScienceIocContainer.ts
+++ b/src/test/datascience/dataScienceIocContainer.ts
@@ -92,7 +92,7 @@ import { PersistentStateFactory } from '../../client/common/persistentState';
 import { IS_WINDOWS } from '../../client/common/platform/constants';
 import { PathUtils } from '../../client/common/platform/pathUtils';
 import { RegistryImplementation } from '../../client/common/platform/registry';
-import { IRegistry } from '../../client/common/platform/types';
+import { IFileSystem, IRegistry } from '../../client/common/platform/types';
 import { CurrentProcess } from '../../client/common/process/currentProcess';
 import { BufferDecoder } from '../../client/common/process/decoder';
 import { ProcessLogger } from '../../client/common/process/logger';
@@ -289,6 +289,7 @@ import { MockCustomEditorService } from './mockCustomEditorService';
 import { MockDebuggerService } from './mockDebugService';
 import { MockDocumentManager } from './mockDocumentManager';
 import { MockExtensions } from './mockExtensions';
+import { MockFileSystem } from './mockFileSystem';
 import { MockJupyterManager, SupportedCommands } from './mockJupyterManager';
 import { MockJupyterManagerFactory } from './mockJupyterManagerFactory';
 import { MockLanguageServerAnalysisOptions } from './mockLanguageServerAnalysisOptions';
@@ -408,6 +409,7 @@ export class DataScienceIocContainer extends UnitTestIocContainer {
         const testWorkspaceFolder = path.join(EXTENSION_ROOT_DIR, 'src', 'test', 'datascience');
 
         this.registerFileSystemTypes();
+        this.serviceManager.rebindInstance<IFileSystem>(IFileSystem, new MockFileSystem());
         this.serviceManager.addSingleton<IJupyterExecution>(IJupyterExecution, JupyterExecutionFactory);
         this.serviceManager.addSingleton<IInteractiveWindowProvider>(IInteractiveWindowProvider, TestInteractiveWindowProvider);
         this.serviceManager.addSingleton<IDataViewerProvider>(IDataViewerProvider, DataViewerProvider);
@@ -763,6 +765,10 @@ export class DataScienceIocContainer extends UnitTestIocContainer {
         this.addInterpreter(this.workingPython2, SupportedCommands.all);
         this.addInterpreter(this.workingPython, SupportedCommands.all);
     }
+    public setFileContents(uri: Uri, contents: string) {
+        const fileSystem = this.serviceManager.get<IFileSystem>(IFileSystem) as MockFileSystem;
+        fileSystem.addFileContents(uri.fsPath, contents);
+    }
 
     public async activate(): Promise<void> {
         // Activate all of the extension activation services
diff --git a/src/test/datascience/mockFileSystem.ts b/src/test/datascience/mockFileSystem.ts
index 7a965dfe9f86..5c03402ea321 100644
--- a/src/test/datascience/mockFileSystem.ts
+++ b/src/test/datascience/mockFileSystem.ts
@@ -2,9 +2,9 @@
 // Licensed under the MIT License.
 'use strict';
 
-import { FileSystem } from '../../client/common/platform/fileSystem';
+import { LegacyFileSystem } from '../serviceRegistry';
 
-export class MockFileSystem extends FileSystem {
+export class MockFileSystem extends LegacyFileSystem {
     private contentOverloads = new Map<string, string>();
 
     constructor() {
diff --git a/src/test/serviceRegistry.ts b/src/test/serviceRegistry.ts
index b32d379a86ed..f1ecf748838f 100644
--- a/src/test/serviceRegistry.ts
+++ b/src/test/serviceRegistry.ts
@@ -67,7 +67,6 @@ import { IServiceContainer, IServiceManager } from '../client/ioc/types';
 import { registerTypes as lintersRegisterTypes } from '../client/linters/serviceRegistry';
 import { TEST_OUTPUT_CHANNEL } from '../client/testing/common/constants';
 import { registerTypes as unittestsRegisterTypes } from '../client/testing/serviceRegistry';
-import { MockFileSystem } from './datascience/mockFileSystem';
 import { MockOutputChannel } from './mockClasses';
 import { MockAutoSelectionService } from './mocks/autoSelector';
 import { MockMemento } from './mocks/mementos';
@@ -95,7 +94,7 @@ class FakeVSCodeFileSystemAPI {
         return convertStat(stat, filetype);
     }
 }
-class LegacyFileSystem extends FileSystem {
+export class LegacyFileSystem extends FileSystem {
     constructor() {
         super();
         const vscfs = new FakeVSCodeFileSystemAPI();
@@ -154,10 +153,6 @@ export class IocContainer {
             this.registerFileSystemTypes();
         }
     }
-    public setFileContents(uri: Uri, contents: string) {
-        const fileSystem = this.serviceManager.get<IFileSystem>(IFileSystem) as MockFileSystem;
-        fileSystem.addFileContents(uri.fsPath, contents);
-    }
     public registerFileSystemTypes() {
         this.serviceManager.addSingleton<IPlatformService>(IPlatformService, PlatformService);
         this.serviceManager.addSingleton<IFileSystem>(