diff --git a/Jakefile.js b/Jakefile.js
index 9b95744d39..1f88ee3908 100644
--- a/Jakefile.js
+++ b/Jakefile.js
@@ -505,9 +505,9 @@ function cleanTestDirs() {
 }
 
 // used to pass data from jake command line directly to run.js
-function writeTestConfigFile(tests, testConfigFile) {
+function writeTestConfigFile(tests, light, testConfigFile) {
     console.log('Running test(s): ' + tests);
-    var testConfigContents = JSON.stringify({ test: [tests]});
+    var testConfigContents = JSON.stringify({ test: [tests], light: light });
     fs.writeFileSync('test.config', testConfigContents);
 }
 
@@ -523,13 +523,14 @@ task("runtests", ["tests", builtLocalDirectory], function() {
     cleanTestDirs();
     host = "mocha"
     tests = process.env.test || process.env.tests || process.env.t;
+    var light = process.env.light || false;
     var testConfigFile = 'test.config';
     if(fs.existsSync(testConfigFile)) {
         fs.unlinkSync(testConfigFile);
     }
 
-    if(tests) {
-        writeTestConfigFile(tests, testConfigFile);
+    if(tests || light) {
+        writeTestConfigFile(tests, light, testConfigFile);
     }
 
     if (tests && tests.toLocaleLowerCase() === "rwc") {
@@ -572,12 +573,13 @@ task("runtests-browser", ["tests", "browserify", builtLocalDirectory], function(
     port = process.env.port || process.env.p || '8888';
     browser = process.env.browser || process.env.b || "IE";
     tests = process.env.test || process.env.tests || process.env.t;
+    var light = process.env.light || false;
     var testConfigFile = 'test.config';
     if(fs.existsSync(testConfigFile)) {
         fs.unlinkSync(testConfigFile);
     }
-    if(tests) {
-        writeTestConfigFile(tests, testConfigFile);
+    if(tests || light) {
+        writeTestConfigFile(tests, light, testConfigFile);
     }
 
     tests = tests ? tests : '';
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 08a6576e5c..7bbfd36bf4 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -11609,7 +11609,9 @@ namespace ts {
 
         function checkSourceFile(node: SourceFile) {
             let start = new Date().getTime();
+
             checkSourceFileWorker(node);
+
             checkTime += new Date().getTime() - start;
         }
 
@@ -11617,6 +11619,8 @@ namespace ts {
         function checkSourceFileWorker(node: SourceFile) {
             let links = getNodeLinks(node);
             if (!(links.flags & NodeCheckFlags.TypeChecked)) {
+                // Check whether the file has declared it is the default lib,
+                // and whether the user has specifically chosen to avoid checking it.
                 if (node.isDefaultLib && compilerOptions.skipDefaultLibCheck) {
                     return;
                 }
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 3478347022..562654c2ed 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -144,21 +144,30 @@ namespace ts {
         let program: Program;
         let files: SourceFile[] = [];
         let diagnostics = createDiagnosticCollection();
-        let skipDefaultLib = options.noLib;
+
         let commonSourceDirectory: string;
         let diagnosticsProducingTypeChecker: TypeChecker;
         let noDiagnosticsTypeChecker: TypeChecker;
         let classifiableNames: Map<string>;
 
+        let skipDefaultLib = options.noLib;
+
         let start = new Date().getTime();
 
         host = host || createCompilerHost(options);
+
         let filesByName = createFileMap<SourceFile>(fileName => host.getCanonicalFileName(fileName));
 
         forEach(rootNames, name => processRootFile(name, /*isDefaultLib:*/ false));
+
+        // Do not process the default library if:
+        //  - The '--noLib' flag is used.
+        //  - A 'no-default-lib' reference comment is encountered in
+        //      processing the root files.
         if (!skipDefaultLib) {
             processRootFile(host.getDefaultLibFileName(options), /*isDefaultLib:*/ true);
         }
+
         verifyCompilerOptions();
 
         programTime += new Date().getTime() - start;
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 8be7c1792a..9c0fd3d0b2 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -1149,6 +1149,14 @@ namespace ts {
         moduleName: string;
         referencedFiles: FileReference[];
 
+        /**
+         * lib.d.ts should have a reference comment like
+         *
+         *  /// <reference no-default-lib="true"/>
+         *
+         * If any other file has this comment, it signals not to include lib.d.ts
+         * because this containing file is intended to act as a default library.
+         */
         hasNoDefaultLib: boolean;
 
         languageVersion: ScriptTarget;
@@ -1860,7 +1868,10 @@ namespace ts {
         experimentalDecorators?: boolean;
         emitDecoratorMetadata?: boolean;
         /* @internal */ stripInternal?: boolean;
+
+        // Skip checking lib.d.ts to help speed up tests.
         /* @internal */ skipDefaultLibCheck?: boolean;
+
         [option: string]: string | number | boolean;
     }
 
diff --git a/src/harness/compilerRunner.ts b/src/harness/compilerRunner.ts
index b6997e705b..21e88b9e41 100644
--- a/src/harness/compilerRunner.ts
+++ b/src/harness/compilerRunner.ts
@@ -1,7 +1,6 @@
 /// <reference path='harness.ts' />
 /// <reference path='runnerbase.ts' />
 /// <reference path='typeWriter.ts' />
-/// <reference path='syntacticCleaner.ts' />
 
 const enum CompilerTestType {
     Conformance,
@@ -18,7 +17,7 @@ class CompilerBaselineRunner extends RunnerBase {
 
     public options: string;
 
-    constructor(public testType?: CompilerTestType) {
+    constructor(public testType: CompilerTestType) {
         super();
         this.errors = true;
         this.emit = true;
@@ -171,7 +170,6 @@ class CompilerBaselineRunner extends RunnerBase {
                 }
             });
 
-
             it('Correct JS output for ' + fileName, () => {
                 if (!ts.fileExtensionIs(lastUnit.name, '.d.ts') && this.emit) {
                     if (result.files.length === 0 && result.errors.length === 0) {
@@ -195,8 +193,6 @@ class CompilerBaselineRunner extends RunnerBase {
                             jsCode += '//// [' + Harness.Path.getFileName(result.files[i].fileName) + ']\r\n';
                             jsCode += getByteOrderMarkText(result.files[i]);
                             jsCode += result.files[i].code;
-                            // Re-enable this if we want to do another comparison of old vs new compiler baselines
-                            // jsCode += SyntacticCleaner.clean(result.files[i].code);
                         }
 
                         if (result.declFilesCode.length > 0) {
diff --git a/src/harness/exec.ts b/src/harness/exec.ts
deleted file mode 100644
index 6ed538b1d4..0000000000
--- a/src/harness/exec.ts
+++ /dev/null
@@ -1,74 +0,0 @@
-//
-// Copyright (c) Microsoft Corporation.  All rights reserved.
-// 
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//   http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-//
-
-// Allows for executing a program with command-line arguments and reading the result
-interface IExec {
-    exec: (fileName: string, cmdLineArgs: string[], handleResult: (ExecResult: ExecResult) => void) => void;
-}
-
-class ExecResult {
-    public stdout = "";
-    public stderr = "";
-    public exitCode: number;
-}
-
-class WindowsScriptHostExec implements IExec {
-    public exec(fileName: string, cmdLineArgs: string[], handleResult: (ExecResult: ExecResult) => void) : void {
-        var result = new ExecResult();
-        var shell = new ActiveXObject('WScript.Shell');
-        try {
-            var process = shell.Exec(fileName + ' ' + cmdLineArgs.join(' '));
-        } catch(e) {
-            result.stderr = e.message;
-            result.exitCode = 1;
-            handleResult(result);
-            return;
-        }
-        // Wait for it to finish running
-        while (process.Status != 0) { /* todo: sleep? */ }
-
-        
-        result.exitCode = process.ExitCode;
-        if(!process.StdOut.AtEndOfStream) result.stdout = process.StdOut.ReadAll();
-        if(!process.StdErr.AtEndOfStream) result.stderr = process.StdErr.ReadAll();
-
-        handleResult(result);
-    }
-}
-
-class NodeExec implements IExec {
-    public exec(fileName: string, cmdLineArgs: string[], handleResult: (ExecResult: ExecResult) => void) : void {
-        var nodeExec = require('child_process').exec;
-
-        var result = new ExecResult();
-        result.exitCode = null;
-        var cmdLine = fileName + ' ' + cmdLineArgs.join(' ');
-        var process = nodeExec(cmdLine, function(error: any, stdout: string, stderr: string) {
-            result.stdout = stdout;
-            result.stderr = stderr;
-            result.exitCode = error ? error.code : 0;
-            handleResult(result);
-        });
-    }
-}
-
-var Exec: IExec = function() : IExec {
-    var global = <any>Function("return this;").call(null);
-    if(typeof global.ActiveXObject !== "undefined") {
-        return new WindowsScriptHostExec();
-    } else {
-        return new NodeExec();
-    }
-}();
\ No newline at end of file
diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index 8d313c9a1a..bf6e120ec3 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -343,7 +343,8 @@ module FourSlash {
                 if (!resolvedResult.isLibFile) {
                     this.languageServiceAdapterHost.addScript(Harness.Compiler.defaultLibFileName, Harness.Compiler.defaultLibSourceFile.text);
                 }
-            } else {
+            }
+            else {
                 // resolveReference file-option is not specified then do not resolve any files and include all inputFiles
                 ts.forEachKey(this.inputFiles, fileName => {
                     if (!Harness.isLibraryFile(fileName)) {
diff --git a/src/harness/harness.ts b/src/harness/harness.ts
index 82afea4cf4..6a55948815 100644
--- a/src/harness/harness.ts
+++ b/src/harness/harness.ts
@@ -99,7 +99,7 @@ module Utils {
         }
 
         try {
-            var content = ts.sys.readFile(Harness.userSpecifiedroot + path);
+            var content = ts.sys.readFile(Harness.userSpecifiedRoot + path);
         }
         catch (err) {
             return undefined;
@@ -732,7 +732,8 @@ module Harness {
     }
 
     // Settings 
-    export var userSpecifiedroot = "";
+    export let userSpecifiedRoot = "";
+    export let lightMode = false;
 
     /** Functionality for compiling TypeScript code */
     export module Compiler {
@@ -809,17 +810,19 @@ module Harness {
         }
 
         export function createSourceFileAndAssertInvariants(
-            fileName: string,
-            sourceText: string,
-            languageVersion: ts.ScriptTarget,
-            assertInvariants: boolean) {
-
+                fileName: string,
+                sourceText: string,
+                languageVersion: ts.ScriptTarget) {
+            // We'll only assert invariants outside of light mode. 
+            const shouldAssertInvariants = !Harness.lightMode;
+            
             // Only set the parent nodes if we're asserting invariants.  We don't need them otherwise.
-            var result = ts.createSourceFile(fileName, sourceText, languageVersion, /*setParentNodes:*/ assertInvariants);
+            var result = ts.createSourceFile(fileName, sourceText, languageVersion, /*setParentNodes:*/ shouldAssertInvariants);
 
-            if (assertInvariants) {
+            if (shouldAssertInvariants) {
                 Utils.assertInvariants(result, /*parent:*/ undefined);
             }
+
             return result;
         }
 
@@ -827,8 +830,8 @@ module Harness {
         const lineFeed = "\n";
 
         export var defaultLibFileName = 'lib.d.ts';
-        export var defaultLibSourceFile = createSourceFileAndAssertInvariants(defaultLibFileName, IO.readFile(libFolder + 'lib.core.d.ts'), /*languageVersion*/ ts.ScriptTarget.Latest, /*assertInvariants:*/ true);
-        export var defaultES6LibSourceFile = createSourceFileAndAssertInvariants(defaultLibFileName, IO.readFile(libFolder + 'lib.core.es6.d.ts'), /*languageVersion*/ ts.ScriptTarget.Latest, /*assertInvariants:*/ true);
+        export var defaultLibSourceFile = createSourceFileAndAssertInvariants(defaultLibFileName, IO.readFile(libFolder + 'lib.core.d.ts'), /*languageVersion*/ ts.ScriptTarget.Latest);
+        export var defaultES6LibSourceFile = createSourceFileAndAssertInvariants(defaultLibFileName, IO.readFile(libFolder + 'lib.core.es6.d.ts'), /*languageVersion*/ ts.ScriptTarget.Latest);
 
         // Cache these between executions so we don't have to re-parse them for every test
         export var fourslashFileName = 'fourslash.ts';
@@ -859,7 +862,7 @@ module Harness {
             function register(file: { unitName: string; content: string; }) {
                 if (file.content !== undefined) {
                     var fileName = ts.normalizePath(file.unitName);
-                    filemap[getCanonicalFileName(fileName)] = createSourceFileAndAssertInvariants(fileName, file.content, scriptTarget, /*assertInvariants:*/ true);
+                    filemap[getCanonicalFileName(fileName)] = createSourceFileAndAssertInvariants(fileName, file.content, scriptTarget);
                 }
             };
             inputFiles.forEach(register);
@@ -882,7 +885,7 @@ module Harness {
                     }
                     else if (fn === fourslashFileName) {
                         var tsFn = 'tests/cases/fourslash/' + fourslashFileName;
-                        fourslashSourceFile = fourslashSourceFile || createSourceFileAndAssertInvariants(tsFn, Harness.IO.readFile(tsFn), scriptTarget, /*assertInvariants:*/ true);
+                        fourslashSourceFile = fourslashSourceFile || createSourceFileAndAssertInvariants(tsFn, Harness.IO.readFile(tsFn), scriptTarget);
                         return fourslashSourceFile;
                     }
                     else {
@@ -939,17 +942,19 @@ module Harness {
             }
 
             public emitAll(ioHost?: IEmitterIOHost) {
-                this.compileFiles(this.inputFiles, [],(result) => {
-                    result.files.forEach(file => {
-                        ioHost.writeFile(file.fileName, file.code, false);
-                    });
-                    result.declFilesCode.forEach(file => {
-                        ioHost.writeFile(file.fileName, file.code, false);
-                    });
-                    result.sourceMaps.forEach(file => {
-                        ioHost.writeFile(file.fileName, file.code, false);
-                    });
-                },() => { }, this.compileOptions);
+                this.compileFiles(this.inputFiles,
+                    /*otherFiles*/ [],
+                    /*onComplete*/ result => {
+                        result.files.forEach(writeFile);
+                        result.declFilesCode.forEach(writeFile);
+                        result.sourceMaps.forEach(writeFile);
+                    },
+                    /*settingsCallback*/ () => { },
+                    this.compileOptions);
+
+                function writeFile(file: GeneratedFile) {
+                    ioHost.writeFile(file.fileName, file.code, false);
+                }
             }
 
             public compileFiles(inputFiles: { unitName: string; content: string }[],
@@ -958,8 +963,7 @@ module Harness {
                 settingsCallback?: (settings: ts.CompilerOptions) => void,
                 options?: ts.CompilerOptions,
                 // Current directory is needed for rwcRunner to be able to use currentDirectory defined in json file
-                currentDirectory?: string,
-                assertInvariants = true) {
+                currentDirectory?: string) {
 
                 options = options || { noResolve: false };
                 options.target = options.target || ts.ScriptTarget.ES3;
@@ -979,7 +983,31 @@ module Harness {
                 var includeBuiltFiles: { unitName: string; content: string }[] = [];
 
                 var useCaseSensitiveFileNames = ts.sys.useCaseSensitiveFileNames;
-                this.settings.forEach(setting => {
+                this.settings.forEach(setCompilerOptionForSetting);
+
+                var fileOutputs: GeneratedFile[] = [];
+
+                var programFiles = inputFiles.concat(includeBuiltFiles).map(file => file.unitName);
+
+                var compilerHost = createCompilerHost(
+                    inputFiles.concat(includeBuiltFiles).concat(otherFiles),
+                    (fn, contents, writeByteOrderMark) => fileOutputs.push({ fileName: fn, code: contents, writeByteOrderMark: writeByteOrderMark }),
+                    options.target, useCaseSensitiveFileNames, currentDirectory, options.newLine);
+                var program = ts.createProgram(programFiles, options, compilerHost);
+
+                var emitResult = program.emit();
+
+                var errors = ts.getPreEmitDiagnostics(program).concat(emitResult.diagnostics);
+                this.lastErrors = errors;
+
+                var result = new CompilerResult(fileOutputs, errors, program, ts.sys.getCurrentDirectory(), emitResult.sourceMaps);
+                onComplete(result, program);
+
+                // reset what newline means in case the last test changed it
+                ts.sys.newLine = newLine;
+                return options;
+                
+                function setCompilerOptionForSetting(setting: Harness.TestCaseParser.CompilerSetting) {
                     switch (setting.flag.toLowerCase()) {
                         // "fileName", "comments", "declaration", "module", "nolib", "sourcemap", "target", "out", "outdir", "noimplicitany", "noresolve"
                         case "module":
@@ -1133,7 +1161,7 @@ module Harness {
                         case 'inlinesourcemap':
                             options.inlineSourceMap = setting.value === 'true';
                             break;
-                        
+
                         case 'inlinesources':
                             options.inlineSources = setting.value === 'true';
                             break;
@@ -1141,28 +1169,7 @@ module Harness {
                         default:
                             throw new Error('Unsupported compiler setting ' + setting.flag);
                     }
-                });
-                
-                var fileOutputs: GeneratedFile[] = [];
-                
-                var programFiles = inputFiles.concat(includeBuiltFiles).map(file => file.unitName);
-                var compilerHost = createCompilerHost(
-                    inputFiles.concat(includeBuiltFiles).concat(otherFiles),
-                    (fn, contents, writeByteOrderMark) => fileOutputs.push({ fileName: fn, code: contents, writeByteOrderMark: writeByteOrderMark }),
-                    options.target, useCaseSensitiveFileNames, currentDirectory, options.newLine);
-                var program = ts.createProgram(programFiles, options, compilerHost);
-
-                var emitResult = program.emit();
-
-                var errors = ts.getPreEmitDiagnostics(program).concat(emitResult.diagnostics);
-                this.lastErrors = errors;
-
-                var result = new CompilerResult(fileOutputs, errors, program, ts.sys.getCurrentDirectory(), emitResult.sourceMaps);
-                onComplete(result, program);
-
-                // reset what newline means in case the last test changed it
-                ts.sys.newLine = newLine;
-                return options;
+                }
             }
 
             public compileDeclarationFiles(inputFiles: { unitName: string; content: string; }[],
@@ -1363,29 +1370,30 @@ module Harness {
                 ts.sys.newLine + ts.sys.newLine + outputLines.join('\r\n');
         }
 
-        export function collateOutputs(outputFiles: Harness.Compiler.GeneratedFile[], clean?: (s: string) => string) {
+        export function collateOutputs(outputFiles: Harness.Compiler.GeneratedFile[]): string {
             // Collect, test, and sort the fileNames
-            function cleanName(fn: string) {
-                var lastSlash = ts.normalizeSlashes(fn).lastIndexOf('/');
-                return fn.substr(lastSlash + 1).toLowerCase();
-            }
             outputFiles.sort((a, b) => cleanName(a.fileName).localeCompare(cleanName(b.fileName)));
 
             // Emit them
             var result = '';
-            ts.forEach(outputFiles, outputFile => {
+            for (let outputFile of outputFiles) {
                 // Some extra spacing if this isn't the first file
-                if (result.length) result = result + '\r\n\r\n';
+                if (result.length) {
+                    result += '\r\n\r\n';
+                }
 
                 // FileName header + content
-                result = result + '/*====== ' + outputFile.fileName + ' ======*/\r\n';
-                if (clean) {
-                    result = result + clean(outputFile.code);
-                } else {
-                    result = result + outputFile.code;
-                }
-            });
+                result += '/*====== ' + outputFile.fileName + ' ======*/\r\n';
+                
+                result += outputFile.code;
+            }
+
             return result;
+
+            function cleanName(fn: string) {
+                var lastSlash = ts.normalizeSlashes(fn).lastIndexOf('/');
+                return fn.substr(lastSlash + 1).toLowerCase();
+            }
         }
 
         /** The harness' compiler instance used when tests are actually run. Reseting or changing settings of this compiler instance must be done within a test case (i.e., describe/it) */
@@ -1487,16 +1495,6 @@ module Harness {
         // Regex for parsing options in the format "@Alpha: Value of any sort"
         var optionRegex = /^[\/]{2}\s*@(\w+)\s*:\s*(\S*)/gm;  // multiple matches on multiple lines
 
-        // List of allowed metadata names
-        var fileMetadataNames = ["filename", "comments", "declaration", "module",
-            "nolib", "sourcemap", "target", "out", "outdir", "noemithelpers", "noemitonerror",
-            "noimplicitany", "noresolve", "newline", "normalizenewline", "emitbom",
-            "errortruncation", "usecasesensitivefilenames", "preserveconstenums",
-            "includebuiltfile", "suppressimplicitanyindexerrors", "stripinternal",
-            "isolatedmodules", "inlinesourcemap", "maproot", "sourceroot",
-            "inlinesources", "emitdecoratormetadata", "experimentaldecorators",
-            "skipdefaultlibcheck"];
-
         function extractCompilerSettings(content: string): CompilerSetting[] {
 
             var opts: CompilerSetting[] = [];
@@ -1530,10 +1528,8 @@ module Harness {
                 if (testMetaData) {
                     // Comment line, check for global/file @options and record them
                     optionRegex.lastIndex = 0;
-                    var fileNameIndex = fileMetadataNames.indexOf(testMetaData[1].toLowerCase());
-                    if (fileNameIndex === -1) {
-                        throw new Error('Unrecognized metadata name "' + testMetaData[1] + '". Available file metadata names are: ' + fileMetadataNames.join(', '));
-                    } else if (fileNameIndex === 0) {
+                    var metaDataName = testMetaData[1].toLowerCase();
+                    if (metaDataName === "filename") {
                         currentFileOptions[testMetaData[1]] = testMetaData[2];
                     } else {
                         continue;
@@ -1619,9 +1615,9 @@ module Harness {
 
         function baselinePath(fileName: string, type: string, baselineFolder: string, subfolder?: string) {
             if (subfolder !== undefined) {
-                return Harness.userSpecifiedroot + baselineFolder + '/' +  subfolder + '/' + type + '/' + fileName;
+                return Harness.userSpecifiedRoot + baselineFolder + '/' +  subfolder + '/' + type + '/' + fileName;
             } else {
-                return Harness.userSpecifiedroot + baselineFolder + '/'  + type + '/' + fileName;
+                return Harness.userSpecifiedRoot + baselineFolder + '/'  + type + '/' + fileName;
             }
         }
 
@@ -1730,7 +1726,7 @@ module Harness {
     }
 
     export function getDefaultLibraryFile(): { unitName: string, content: string } {
-        var libFile = Harness.userSpecifiedroot + Harness.libFolder + "/" + "lib.d.ts";
+        var libFile = Harness.userSpecifiedRoot + Harness.libFolder + "/" + "lib.d.ts";
         return {
             unitName: libFile,
             content: IO.readFile(libFile)
diff --git a/src/harness/project.ts b/src/harness/project.ts
deleted file mode 100644
index d94cbd576d..0000000000
--- a/src/harness/project.ts
+++ /dev/null
@@ -1,19 +0,0 @@
-//
-// Copyright (c) Microsoft Corporation.  All rights reserved.
-// 
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//   http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-//
-
-/// <reference path="exec.ts" />
-/// <reference path="generate.ts" />
-/// <reference path="harness.ts" />
-/// <reference path="diff.ts" />
diff --git a/src/harness/projectsRunner.ts b/src/harness/projectsRunner.ts
index cb454c00e6..324524272e 100644
--- a/src/harness/projectsRunner.ts
+++ b/src/harness/projectsRunner.ts
@@ -174,7 +174,7 @@ class ProjectRunner extends RunnerBase {
                 else {
                     var text = getSourceFileText(fileName);
                     if (text !== undefined) {
-                        sourceFile = Harness.Compiler.createSourceFileAndAssertInvariants(fileName, text, languageVersion, /*assertInvariants:*/ true);
+                        sourceFile = Harness.Compiler.createSourceFileAndAssertInvariants(fileName, text, languageVersion);
                     }
                 }
 
diff --git a/src/harness/runner.ts b/src/harness/runner.ts
index eae4d77bb2..42c2d5667c 100644
--- a/src/harness/runner.ts
+++ b/src/harness/runner.ts
@@ -18,6 +18,7 @@
 /// <reference path='fourslashRunner.ts' />
 /// <reference path='projectsRunner.ts' />
 /// <reference path='rwcRunner.ts' />
+/// <reference path='harness.ts' />
 
 function runTests(runners: RunnerBase[]) {
     for (var i = iterations; i > 0; i--) {
@@ -39,6 +40,9 @@ var testConfigFile =
 
 if (testConfigFile !== '') {
     var testConfig = JSON.parse(testConfigFile);
+    if (testConfig.light) {
+        Harness.lightMode = true;
+    }
 
     if (testConfig.test && testConfig.test.length > 0) {
         for (let option of testConfig.test) {
diff --git a/src/harness/runnerbase.ts b/src/harness/runnerbase.ts
index 49ca796448..269e889704 100644
--- a/src/harness/runnerbase.ts
+++ b/src/harness/runnerbase.ts
@@ -12,7 +12,7 @@ class RunnerBase {
     }
 
     public enumerateFiles(folder: string, regex?: RegExp, options?: { recursive: boolean }): string[] {
-        return Harness.IO.listFiles(Harness.userSpecifiedroot + folder, regex, { recursive: (options ? options.recursive : false) });
+        return Harness.IO.listFiles(Harness.userSpecifiedRoot + folder, regex, { recursive: (options ? options.recursive : false) });
     }
 
     /** Setup the runner's tests so that they are ready to be executed by the harness 
diff --git a/src/harness/rwcRunner.ts b/src/harness/rwcRunner.ts
index 49a15112e9..43a118b6ae 100644
--- a/src/harness/rwcRunner.ts
+++ b/src/harness/rwcRunner.ts
@@ -1,6 +1,5 @@
 /// <reference path='harness.ts'/>
 /// <reference path='runnerbase.ts' />
-/// <reference path='syntacticCleaner.ts' />
 /// <reference path='loggedIO.ts' />
 /// <reference path='..\compiler\commandLineParser.ts'/>
 
@@ -75,7 +74,7 @@ module RWC {
                     });
 
                     // Add files to compilation
-                    for(let fileRead of ioLog.filesRead) {
+                    for (let fileRead of ioLog.filesRead) {
                         // Check if the file is already added into the set of input files.
                         var resolvedPath = ts.normalizeSlashes(ts.sys.resolvePath(fileRead.path));
                         var inInputList = ts.forEach(inputFiles, inputFile => inputFile.unitName === resolvedPath);
@@ -107,14 +106,14 @@ module RWC {
                     opts.options.noLib = true;
 
                     // Emit the results
-                    compilerOptions = harnessCompiler.compileFiles(inputFiles, otherFiles, compileResult => {
-                        compilerResult = compileResult;
-                        },
+                    compilerOptions = harnessCompiler.compileFiles(
+                        inputFiles,
+                        otherFiles,
+                        newCompilerResults => { compilerResult = newCompilerResults; },
                         /*settingsCallback*/ undefined, opts.options,
-                        // Since all Rwc json file specified current directory in its json file, we need to pass this information to compilerHost
-                        // so that when the host is asked for current directory, it should give the value from json rather than from process
-                        currentDirectory,
-                        /*assertInvariants:*/ false);
+                        // Since each RWC json file specifies its current directory in its json file, we need
+                        // to pass this information in explicitly instead of acquiring it from the process.
+                        currentDirectory);
                 });
 
                 function getHarnessCompilerInputUnit(fileName: string) {
@@ -132,7 +131,7 @@ module RWC {
 
             it('has the expected emitted code', () => {
                 Harness.Baseline.runBaseline('has the expected emitted code', baseName + '.output.js', () => {
-                    return Harness.Compiler.collateOutputs(compilerResult.files, s => SyntacticCleaner.clean(s));
+                    return Harness.Compiler.collateOutputs(compilerResult.files);
                 }, false, baselineOpts);
             });
 
diff --git a/src/harness/syntacticCleaner.ts b/src/harness/syntacticCleaner.ts
deleted file mode 100644
index 05b4295124..0000000000
--- a/src/harness/syntacticCleaner.ts
+++ /dev/null
@@ -1,30 +0,0 @@
-// Use this to get emitter-agnostic baselines
-
-class SyntacticCleaner {
-    static clean(sourceFileContents: string) {
-        return sourceFileContents;
-    }
-}
-
-/* TODO: Re-implement or maybe delete
-class SyntacticCleaner extends TypeScript.SyntaxWalker {
-    private emit: string[] = [];
-
-    public visitToken(token: TypeScript.ISyntaxToken): void {
-        this.emit.push(token.text());
-        if (token.kind() === TypeScript.SyntaxKind.SemicolonToken) {
-            this.emit.push('\r\n');
-        } else {
-            this.emit.push(' ');
-
-        }
-    }
-
-    static clean(sourceFileContents: string): string {
-        var parsed = TypeScript.Parser.parse('_emitted.ts', TypeScript.SimpleText.fromString(sourceFileContents), TypeScript.LanguageVersion.EcmaScript5, false);
-        var cleaner = new SyntacticCleaner();
-        cleaner.visitSourceUnit(parsed.sourceUnit());
-        return cleaner.emit.join('');
-    }
-}
-*/
diff --git a/src/harness/test262Runner.ts b/src/harness/test262Runner.ts
index 0091da5e91..5f8250c5e2 100644
--- a/src/harness/test262Runner.ts
+++ b/src/harness/test262Runner.ts
@@ -1,6 +1,5 @@
 /// <reference path='harness.ts' />
 /// <reference path='runnerbase.ts' />
-/// <reference path='syntacticCleaner.ts' />
 
 class Test262BaselineRunner extends RunnerBase {
     private static basePath = 'internal/cases/test262';
@@ -65,7 +64,7 @@ class Test262BaselineRunner extends RunnerBase {
             it('has the expected emitted code', () => {
                 Harness.Baseline.runBaseline('has the expected emitted code', testState.filename + '.output.js', () => {
                     var files = testState.compilerResult.files.filter(f=> f.fileName !== Test262BaselineRunner.helpersFilePath);
-                    return Harness.Compiler.collateOutputs(files, s => SyntacticCleaner.clean(s));
+                    return Harness.Compiler.collateOutputs(files);
                 }, false, Test262BaselineRunner.baselineOptions);
             });
 
diff --git a/tests/baselines/reference/parser509698.errors.txt b/tests/baselines/reference/parser509698.errors.txt
index 2aaaec18dc..dfc155dd36 100644
--- a/tests/baselines/reference/parser509698.errors.txt
+++ b/tests/baselines/reference/parser509698.errors.txt
@@ -18,7 +18,6 @@ error TS2318: Cannot find global type 'String'.
 !!! error TS2318: Cannot find global type 'String'.
 ==== tests/cases/conformance/parser/ecmascript5/RegressionTests/parser509698.ts (0 errors) ====
     /// <style requireSemi="on" />
-    /// <reference no-default-lib="true"/>
     declare function foo(): void;
     declare function bar(): void;
     
\ No newline at end of file
diff --git a/tests/baselines/reference/parser509698.js b/tests/baselines/reference/parser509698.js
index a1b6810a43..5349b9aec9 100644
--- a/tests/baselines/reference/parser509698.js
+++ b/tests/baselines/reference/parser509698.js
@@ -1,6 +1,5 @@
 //// [parser509698.ts]
 /// <style requireSemi="on" />
-/// <reference no-default-lib="true"/>
 declare function foo(): void;
 declare function bar(): void;
 
diff --git a/tests/cases/conformance/parser/ecmascript5/RegressionTests/parser509698.ts b/tests/cases/conformance/parser/ecmascript5/RegressionTests/parser509698.ts
index f33abc85b5..7ae67975b2 100644
--- a/tests/cases/conformance/parser/ecmascript5/RegressionTests/parser509698.ts
+++ b/tests/cases/conformance/parser/ecmascript5/RegressionTests/parser509698.ts
@@ -1,4 +1,4 @@
+// @noLib: true
 /// <style requireSemi="on" />
-/// <reference no-default-lib="true"/>
 declare function foo(): void;
 declare function bar(): void;
diff --git a/tests/cases/unittests/convertToBase64.ts b/tests/cases/unittests/convertToBase64.ts
index 96c082ae78..76f56f7747 100644
--- a/tests/cases/unittests/convertToBase64.ts
+++ b/tests/cases/unittests/convertToBase64.ts
@@ -1,4 +1,4 @@
-/// <reference path="..\..\..\src\harness\harness.ts" />
+/// <reference path="..\..\..\src\harness\harness.ts" />
 
 module ts {
     describe('convertToBase64', () => {
@@ -8,25 +8,25 @@ module ts {
             assert.equal(actual, expected, "Encoded string using convertToBase64 does not match buffer.toString('base64')");
         }
 
-        it("Converts ASCII charaters correctelly", () => {
+        it("Converts ASCII charaters correctly", () => {
             runTest(" !\"#$ %&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~");
         });
 
-        it("Converts escape sequences correctelly", () => {
+        it("Converts escape sequences correctly", () => {
             runTest("\t\n\r\\\"\'\u0062");
         });
 
-        it("Converts simple unicode characters correctelly", () => {
+        it("Converts simple unicode characters correctly", () => {
             runTest("ΠΣ ٵپ औठ ⺐⺠");
         });
 
-        it("Converts simple code snippit correctelly", () => {
+        it("Converts simple code snippet correctly", () => {
             runTest(`/// <reference path="file.ts" /> 
 var x: string = "string";
 console.log(x);`);
         });
 
-        it("Converts simple code snippit with unicode characters correctelly", () => {
+        it("Converts simple code snippet with unicode characters correctly", () => {
             runTest(`var Π = 3.1415; console.log(Π);`);
         });
     });
diff --git a/tests/cases/unittests/transpile.ts b/tests/cases/unittests/transpile.ts
index 47f8bd04cb..06754a5bbc 100644
--- a/tests/cases/unittests/transpile.ts
+++ b/tests/cases/unittests/transpile.ts
@@ -1,4 +1,4 @@
-/// <reference path="..\..\..\src\harness\harness.ts" />
+/// <reference path="..\..\..\src\harness\harness.ts" />
 
 module ts {
     describe("Transpile", () => {