diff --git a/src/testRunner/tsconfig.json b/src/testRunner/tsconfig.json
index 3e25598e77c..f763f432cac 100644
--- a/src/testRunner/tsconfig.json
+++ b/src/testRunner/tsconfig.json
@@ -234,6 +234,7 @@
         "unittests/tsserver/typeOnlyImportChains.ts",
         "unittests/tsserver/typeReferenceDirectives.ts",
         "unittests/tsserver/typingsInstaller.ts",
+        "unittests/tsserver/updateFileSystem.ts",
         "unittests/tsserver/versionCache.ts",
         "unittests/tsserver/watchEnvironment.ts",
         "unittests/tsserver/webServer.ts",
diff --git a/src/testRunner/unittests/tsserver/applyChangesToOpenFiles.ts b/src/testRunner/unittests/tsserver/applyChangesToOpenFiles.ts
index 863a2333329..6d5ee91d68d 100644
--- a/src/testRunner/unittests/tsserver/applyChangesToOpenFiles.ts
+++ b/src/testRunner/unittests/tsserver/applyChangesToOpenFiles.ts
@@ -1,108 +1,4 @@
 namespace ts.projectSystem {
-    // TODO: Make a separate file at some point
-    describe("unittests:: tsserver:: updateFileSystem", () => {
-        const config: protocol.FileSystemRequestArgs = {
-            file: "/a/b/tsconfig.json",
-            fileContent: "{}"
-        };
-        const file3: protocol.FileSystemRequestArgs = {
-            file: "/a/b/file3.ts",
-            fileContent: "export let xyz = 1;"
-        };
-        const app: protocol.FileSystemRequestArgs = {
-            file: "/a/b/app.ts",
-            fileContent: "import { xyz } from './file3'; let x = xyz"
-        };
-        const file1: protocol.FileSystemRequestArgs = {
-            file: "/a/b/commonFile1.ts",
-            fileContent: "let x = 1"
-        };
-        const file2: protocol.FileSystemRequestArgs = {
-            file: "/a/b/commonFile2.ts",
-            fileContent: "let y = 1"
-        };
-        const lib: protocol.FileSystemRequestArgs = {
-        file: "/a/lib/lib.d.ts",
-        fileContent: `/// <reference no-default-lib="true"/>
-interface Boolean {}
-interface Function {}
-interface CallableFunction {}
-interface NewableFunction {}
-interface IArguments {}
-interface Number { toExponential: any; }
-interface Object {}
-interface RegExp {}
-interface String { charAt: any; }
-interface Array<T> { length: number; [n: number]: T; }`
-    };
-
-        function fileContentWithComment(file: protocol.FileSystemRequestArgs) {
-            return `// some copy right notice
-${file.fileContent}`;
-        }
-        function baselineFileSystem(scenario: string, subScenario: string, requests: [string, Partial<protocol.Request>][], host: VirtualFS.VirtualServerHost, session: TestSession) {
-            const history: string[] = []
-            let prev = host.snap()
-            for (const [name, request] of requests) {
-                session.executeCommandSeq(request)
-                history.push("")
-                history.push("#### " + name)
-                host.diff(history, prev)
-                prev = host.snap()
-            }
-            Harness.Baseline.runBaseline(`tsserver/${scenario}/${subScenario.split(" ").join("-")}.txt`, history.join("\r\n"));
-            baselineTsserverLogs(scenario, subScenario, session)
-        }
-
-        it("with updateFileSystem request", () => {
-            const host = VirtualFS.createVirtualServerHost({ executingFilePath: "/a/tsc.js" });
-            const session = createSession(host, { fshost: host, logger: createLoggerWithInMemoryLogs(), canUseEvents: true });
-            const requests: [string, Partial<protocol.Request>][] = [
-                ["Initial updateFileSystem", {
-                    command: protocol.CommandTypes.UpdateFileSystem,
-                    arguments:{
-                        fileSystem: "memfs",
-                        files: [app, file1, file2, file3, config, lib],
-                        deleted: [],
-                    }
-                }],
-                ["Opening app.ts", {
-                    command: protocol.CommandTypes.Open,
-                    arguments: { file: app.file }
-                }],
-                ["Opening file3.ts", {
-                    command: protocol.CommandTypes.Open,
-                    arguments: {
-                        file: file3.file,
-                        fileContent: fileContentWithComment(file3)
-                    }
-                }],
-                ["non-delete", {
-                    command: protocol.CommandTypes.UpdateFileSystem,
-                    arguments:{
-                        fileSystem: "memfs",
-                        files: [],
-                        deleted: [],
-                    }
-                }],
-                ["delete", {
-                    command: protocol.CommandTypes.UpdateFileSystem,
-                    arguments:{
-                        fileSystem: "memfs",
-                        files: [],
-                        deleted: [file1.file],
-                    }
-                }],
-                ["close", {
-                    command: protocol.CommandTypes.Close,
-                    arguments: { file: app.file }
-                }],
-            ]
-            const scenario = "updateFileSystem"
-            const subScenario = "open and close files"
-            baselineFileSystem(scenario, subScenario, requests, host, session);
-        });
-    });
     describe("unittests:: tsserver:: applyChangesToOpenFiles", () => {
         const configFile: File = {
             path: "/a/b/tsconfig.json",
diff --git a/src/testRunner/unittests/tsserver/updateFileSystem.ts b/src/testRunner/unittests/tsserver/updateFileSystem.ts
new file mode 100644
index 00000000000..4d5cba2ad2e
--- /dev/null
+++ b/src/testRunner/unittests/tsserver/updateFileSystem.ts
@@ -0,0 +1,105 @@
+namespace ts.projectSystem {
+    describe("unittests:: tsserver:: updateFileSystem", () => {
+        const config: protocol.FileSystemRequestArgs = {
+            file: "/a/b/tsconfig.json",
+            fileContent: "{}"
+        };
+        const file3: protocol.FileSystemRequestArgs = {
+            file: "/a/b/file3.ts",
+            fileContent: "export let xyz = 1;"
+        };
+        const app: protocol.FileSystemRequestArgs = {
+            file: "/a/b/app.ts",
+            fileContent: "import { xyz } from './file3'; let x = xyz"
+        };
+        const file1: protocol.FileSystemRequestArgs = {
+            file: "/a/b/commonFile1.ts",
+            fileContent: "let x = 1"
+        };
+        const file2: protocol.FileSystemRequestArgs = {
+            file: "/a/b/commonFile2.ts",
+            fileContent: "let y = 1"
+        };
+        const lib: protocol.FileSystemRequestArgs = {
+        file: "/a/lib/lib.d.ts",
+        fileContent: `/// <reference no-default-lib="true"/>
+interface Boolean {}
+interface Function {}
+interface CallableFunction {}
+interface NewableFunction {}
+interface IArguments {}
+interface Number { toExponential: any; }
+interface Object {}
+interface RegExp {}
+interface String { charAt: any; }
+interface Array<T> { length: number; [n: number]: T; }`
+    };
+
+        function fileContentWithComment(file: protocol.FileSystemRequestArgs) {
+            return `// some copy right notice
+${file.fileContent}`;
+        }
+        function baselineFileSystem(scenario: string, subScenario: string, requests: [string, Partial<protocol.Request>][], host: VirtualFS.VirtualServerHost, session: TestSession) {
+            const history: string[] = []
+            let prev = host.snap()
+            for (const [name, request] of requests) {
+                session.executeCommandSeq(request)
+                history.push("")
+                history.push("#### " + name)
+                host.diff(history, prev)
+                prev = host.snap()
+            }
+            Harness.Baseline.runBaseline(`tsserver/${scenario}/${subScenario.split(" ").join("-")}.txt`, history.join("\r\n"));
+            baselineTsserverLogs(scenario, subScenario, session)
+        }
+
+        it("with updateFileSystem request", () => {
+            const host = VirtualFS.createVirtualServerHost({ executingFilePath: "/a/tsc.js" });
+            const session = createSession(host, { fshost: host, logger: createLoggerWithInMemoryLogs(), canUseEvents: true });
+            const requests: [string, Partial<protocol.Request>][] = [
+                ["Initial updateFileSystem", {
+                    command: protocol.CommandTypes.UpdateFileSystem,
+                    arguments:{
+                        fileSystem: "memfs",
+                        files: [app, file1, file2, file3, config, lib],
+                        deleted: [],
+                    }
+                }],
+                ["Opening app.ts", {
+                    command: protocol.CommandTypes.Open,
+                    arguments: { file: app.file }
+                }],
+                ["Opening file3.ts", {
+                    command: protocol.CommandTypes.Open,
+                    arguments: {
+                        file: file3.file,
+                        fileContent: fileContentWithComment(file3)
+                    }
+                }],
+                ["non-delete", {
+                    command: protocol.CommandTypes.UpdateFileSystem,
+                    arguments:{
+                        fileSystem: "memfs",
+                        files: [],
+                        deleted: [],
+                    }
+                }],
+                ["delete", {
+                    command: protocol.CommandTypes.UpdateFileSystem,
+                    arguments:{
+                        fileSystem: "memfs",
+                        files: [],
+                        deleted: [file1.file],
+                    }
+                }],
+                ["close", {
+                    command: protocol.CommandTypes.Close,
+                    arguments: { file: app.file }
+                }],
+            ]
+            const scenario = "updateFileSystem"
+            const subScenario = "open and close files"
+            baselineFileSystem(scenario, subScenario, requests, host, session);
+        });
+    });
+}