diff --git a/extensions/typescript-language-features/src/tsServer/server.ts b/extensions/typescript-language-features/src/tsServer/server.ts
index 10a001d52c2..125c541fe0f 100644
--- a/extensions/typescript-language-features/src/tsServer/server.ts
+++ b/extensions/typescript-language-features/src/tsServer/server.ts
@@ -109,7 +109,7 @@ export class TypeScriptServerSpawner {
 		version: TypeScriptVersion,
 		configuration: TypeScriptServiceConfiguration,
 		pluginManager: PluginManager
-	): TypeScriptServer {
+	): ITypeScriptServer {
 		const apiVersion = version.version || API.defaultVersion;
 
 		const { args, cancellationPipeName, tsServerLogFile } = this.getTsServerArgs(configuration, version, apiVersion, pluginManager);
@@ -303,7 +303,24 @@ class ChildServerProcess implements ServerProcess {
 	}
 }
 
-export class TypeScriptServer extends Disposable {
+export interface ITypeScriptServer {
+	readonly onEvent: vscode.Event<Proto.Event>;
+	readonly onExit: vscode.Event<any>;
+	readonly onError: vscode.Event<any>;
+	readonly onReaderError: vscode.Event<Error>;
+
+	readonly tsServerLogFile: string | undefined;
+
+	kill(): void;
+
+	executeImpl(command: string, args: any, executeInfo: { isAsync: boolean, token?: vscode.CancellationToken, expectsResult: false, lowPriority?: boolean }): undefined;
+	executeImpl(command: string, args: any, executeInfo: { isAsync: boolean, token?: vscode.CancellationToken, expectsResult: boolean, lowPriority?: boolean }): Promise<ServerResponse.Response<Proto.Response>>;
+	executeImpl(command: string, args: any, executeInfo: { isAsync: boolean, token?: vscode.CancellationToken, expectsResult: boolean, lowPriority?: boolean }): Promise<ServerResponse.Response<Proto.Response>> | undefined;
+
+	dispose(): void;
+}
+
+export class TypeScriptServer extends Disposable implements ITypeScriptServer {
 	private readonly _reader: Reader<Proto.Response>;
 	private readonly _requestQueue = new RequestQueue();
 	private readonly _callbacks = new CallbackMap<Proto.Response>();
diff --git a/extensions/typescript-language-features/src/typescriptServiceClient.ts b/extensions/typescript-language-features/src/typescriptServiceClient.ts
index b478e9ed080..2849cfcd012 100644
--- a/extensions/typescript-language-features/src/typescriptServiceClient.ts
+++ b/extensions/typescript-language-features/src/typescriptServiceClient.ts
@@ -10,7 +10,7 @@ import * as nls from 'vscode-nls';
 import BufferSyncSupport from './features/bufferSyncSupport';
 import { DiagnosticKind, DiagnosticsManager } from './features/diagnostics';
 import * as Proto from './protocol';
-import { TypeScriptServer, TypeScriptServerSpawner } from './tsServer/server';
+import { ITypeScriptServer, TypeScriptServerSpawner } from './tsServer/server';
 import { ITypeScriptServiceClient, ServerResponse } from './typescriptService';
 import API from './utils/api';
 import { TsServerLogLevel, TypeScriptServiceConfiguration } from './utils/configuration';
@@ -46,7 +46,7 @@ namespace ServerState {
 	export class Running {
 		readonly type = Type.Running;
 		constructor(
-			public readonly server: TypeScriptServer,
+			public readonly server: ITypeScriptServer,
 
 			/**
 			 * API version obtained from the version picker after checking the corresponding path exists.