diff --git a/src/harness/harness.ts b/src/harness/harness.ts
index f65a4f88730..2493eec867b 100644
--- a/src/harness/harness.ts
+++ b/src/harness/harness.ts
@@ -428,6 +428,7 @@ module Harness {
         args(): string[];
         getExecutingFilePath(): string;
         exit(exitCode?: number): void;
+        readDirectory(path: string, extension?: string, exclude?: string[]): string[];
     }
     export var IO: IO;
     
@@ -464,6 +465,7 @@ module Harness {
             export const directoryExists: typeof IO.directoryExists = fso.FolderExists;
             export const fileExists: typeof IO.fileExists = fso.FileExists;
             export const log: typeof IO.log = global.WScript && global.WScript.StdOut.WriteLine;
+            export const readDirectory: typeof IO.readDirectory = (path, extension, exclude) => ts.sys.readDirectory(path, extension, exclude);
 
             export function createDirectory(path: string) {
                 if (directoryExists(path)) {
@@ -532,6 +534,8 @@ module Harness {
             export const fileExists: typeof IO.fileExists = fs.existsSync;
             export const log: typeof IO.log = s => console.log(s);
 
+            export const readDirectory: typeof IO.readDirectory = (path, extension, exclude) => ts.sys.readDirectory(path, extension, exclude);
+
             export function createDirectory(path: string) {
                 if (!directoryExists(path)) {
                     fs.mkdirSync(path);
@@ -730,6 +734,10 @@ module Harness {
             export function writeFile(path: string, contents: string) {
                 Http.writeToServerSync(serverRoot + path, "WRITE", contents);
             }
+
+            export function readDirectory(path: string, extension?: string, exclude?: string[]) {
+                return listFiles(path).filter(f => !extension || ts.fileExtensionIs(f, extension));
+            }
         }
     }
 
diff --git a/src/harness/loggedIO.ts b/src/harness/loggedIO.ts
index 3d1833b061f..38c9cc7e795 100644
--- a/src/harness/loggedIO.ts
+++ b/src/harness/loggedIO.ts
@@ -59,6 +59,12 @@ interface IOLog {
         path: string;
         result?: string;
     }[];
+    directoriesRead: {
+        path: string,
+        extension: string,
+        exclude: string[],
+        result: string[]
+    }[];
 }
 
 interface PlaybackControl {
@@ -103,6 +109,7 @@ module Playback {
             arguments: [],
             currentDirectory: "",
             filesRead: [],
+            directoriesRead: [],
             filesWritten: [],
             filesDeleted: [],
             filesAppended: [],
@@ -118,7 +125,7 @@ module Playback {
 
     function initWrapper(wrapper: PlaybackSystem, underlying: ts.System): void;
     function initWrapper(wrapper: PlaybackIO, underlying: Harness.IO): void;
-    function initWrapper(wrapper: PlaybackSystem | PlaybackIO, underlying: ts.System | Harness.IO): void  {
+    function initWrapper(wrapper: PlaybackSystem | PlaybackIO, underlying: ts.System | Harness.IO): void {
         ts.forEach(Object.keys(underlying), prop => {
             (<any>wrapper)[prop] = (<any>underlying)[prop];
         });
@@ -203,6 +210,15 @@ module Playback {
             },
             memoize((path) => findResultByPath(wrapper, replayLog.filesRead, path).contents));
 
+        wrapper.readDirectory = recordReplay(wrapper.readDirectory, underlying)(
+            (path, extension, exclude) => {
+                let result = (<ts.System>underlying).readDirectory(path, extension, exclude);
+                let logEntry = { path, extension, exclude, result };
+                recordLog.directoriesRead.push(logEntry);
+                return result;
+            },
+            (path, extension, exclude) => findResultByPath(wrapper, replayLog.directoriesRead.filter(d => d.extension === extension && ts.arrayIsEqualTo(d.exclude, exclude)), path));
+
         wrapper.writeFile = recordReplay(wrapper.writeFile, underlying)(
             (path, contents) => callAndRecord(underlying.writeFile(path, contents), recordLog.filesWritten, { path: path, contents: contents, bom: false }),
             (path, contents) => noOpReplay("writeFile"));
diff --git a/src/harness/rwcRunner.ts b/src/harness/rwcRunner.ts
index a1aaeed3d55..8bfb8400c59 100644
--- a/src/harness/rwcRunner.ts
+++ b/src/harness/rwcRunner.ts
@@ -19,6 +19,11 @@ module RWC {
         }
     }
 
+    function isTsConfigFile(file: { path: string }): boolean {
+        const tsConfigFileName = "tsconfig.json";
+        return file.path.substr(file.path.length - tsConfigFileName.length).toLowerCase() === tsConfigFileName;
+    }
+
     export function runRWCTest(jsonPath: string) {
         describe("Testing a RWC project: " + jsonPath, () => {
             let inputFiles: { unitName: string; content: string; }[] = [];
@@ -67,8 +72,17 @@ module RWC {
                 runWithIOLog(ioLog, oldIO => {
                     harnessCompiler.reset();
 
+                    let fileNames = opts.fileNames;
+
+                    let tsconfigFile = ts.forEach(ioLog.filesRead, f => isTsConfigFile(f) ? f : undefined);
+                    if (tsconfigFile) {
+                        let tsconfigFileContents = getHarnessCompilerInputUnit(tsconfigFile.path);
+                        let configParseResult = ts.parseConfigFile(tsconfigFileContents.content, Harness.IO, ts.getDirectoryPath(tsconfigFile.path));
+                        fileNames = configParseResult.fileNames;
+                    }
+
                     // Load the files
-                    ts.forEach(opts.fileNames, fileName => {
+                    ts.forEach(fileNames, fileName => {
                         inputFiles.push(getHarnessCompilerInputUnit(fileName));
                     });
 
@@ -79,6 +93,10 @@ module RWC {
                         const resolvedPath = ts.normalizeSlashes(Harness.IO.resolvePath(fileRead.path));
                         let inInputList = ts.forEach(inputFiles, isInInputList(resolvedPath));
 
+                        if (isTsConfigFile(fileRead)) {
+                            continue;
+                        }
+
                         if (!Harness.isLibraryFile(fileRead.path)) {
                             if (inInputList) {
                                 continue;