diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index b01c2e6efc3..191479b1fae 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -506,7 +506,7 @@ namespace ts {
             container = saveContainer;
             blockScopeContainer = savedBlockScopeContainer;
         }
-        
+
         function bindChildren(node: Node): void {
             if (skipTransformFlagAggregation) {
                 bindChildrenWorker(node);
diff --git a/src/compiler/transformers/ts.ts b/src/compiler/transformers/ts.ts
index 12e6461c28b..72a80b11600 100644
--- a/src/compiler/transformers/ts.ts
+++ b/src/compiler/transformers/ts.ts
@@ -627,7 +627,7 @@ namespace ts {
             //  ... = class ${name} ${heritageClauses} {
             //      ${members}
             //  }
-            let classExpression: Expression = setOriginalNode(
+            const classExpression: Expression = setOriginalNode(
                 createClassExpression(
                     name,
                     visitNodes(node.heritageClauses, visitor, isHeritageClause),
diff --git a/src/harness/harness.ts b/src/harness/harness.ts
index 49dcab4d80b..caafe629f30 100644
--- a/src/harness/harness.ts
+++ b/src/harness/harness.ts
@@ -769,7 +769,7 @@ namespace Harness {
                     return response.responseText;
                 }
                 else {
-                    return null;
+                    return undefined;
                 }
             }
 
diff --git a/src/harness/projectsRunner.ts b/src/harness/projectsRunner.ts
index 21f3f144b74..4bfd75c1dd0 100644
--- a/src/harness/projectsRunner.ts
+++ b/src/harness/projectsRunner.ts
@@ -472,7 +472,7 @@ class ProjectRunner extends RunnerBase {
 
                     it("Baseline of emitted result (" + moduleNameToString(moduleKind) + "): " + testCaseFileName, () => {
                         if (testCase.baselineCheck) {
-                            var lastError: any = undefined;
+                            let lastError: any = undefined;
                             ts.forEach(compilerResult.outputFiles, outputFile => {
                                 try {
                                     Harness.Baseline.runBaseline("Baseline of emitted result (" + moduleNameToString(compilerResult.moduleKind) + "): " + testCaseFileName, getBaselineFolder(compilerResult.moduleKind) + outputFile.fileName, () => {
diff --git a/tests/cases/unittests/jsDocParsing.ts b/tests/cases/unittests/jsDocParsing.ts
index a99f1bad881..f87b20f804f 100644
--- a/tests/cases/unittests/jsDocParsing.ts
+++ b/tests/cases/unittests/jsDocParsing.ts
@@ -3,7 +3,7 @@
 /// <reference path="..\..\..\src\compiler\parser.ts" />
 /// <reference path="..\..\..\src\harness\harness.ts" />
 
-module ts {
+namespace ts {
     describe("JSDocParsing", () => {
         describe("TypeExpressions", () => {
             function parsesCorrectly(name: string, content: string) {
@@ -95,10 +95,10 @@ module ts {
                 it(name, () => {
                     const comment = parseIsolatedJSDocComment(content);
                     if (!comment) {
-                        Debug.fail('Comment failed to parse entirely');
+                        Debug.fail("Comment failed to parse entirely");
                     }
                     if (comment.diagnostics.length > 0) {
-                        Debug.fail('Comment has at least one diagnostic: ' + comment.diagnostics[0].messageText);
+                        Debug.fail("Comment has at least one diagnostic: " + comment.diagnostics[0].messageText);
                     }
 
                     Harness.Baseline.runBaseline("parseCorrectly", "JSDocParsing/DocComments.parsesCorrectly." + name + ".json",
@@ -118,29 +118,29 @@ module ts {
                 parsesIncorrectly("emptyComment", "/***/");
                 parsesIncorrectly("threeAsterisks", "/*** */");
                 parsesIncorrectly("asteriskAfterPreamble", "/** * @type {number} */");
-                parsesIncorrectly("multipleTypes", 
+                parsesIncorrectly("multipleTypes",
                         `/**
   * @type {number}
   * @type {string}
   */`);
-                parsesIncorrectly("multipleReturnTypes", 
+                parsesIncorrectly("multipleReturnTypes",
                         `/**
   * @return {number}
   * @return {string}
   */`);
-                parsesIncorrectly("noTypeParameters", 
+                parsesIncorrectly("noTypeParameters",
                         `/**
   * @template
   */`);
-                parsesIncorrectly("trailingTypeParameterComma", 
+                parsesIncorrectly("trailingTypeParameterComma",
                         `/**
   * @template T,
   */`);
-                parsesIncorrectly("paramWithoutName", 
+                parsesIncorrectly("paramWithoutName",
                         `/**
   * @param {number}
   */`);
-                parsesIncorrectly("paramWithoutTypeOrName", 
+                parsesIncorrectly("paramWithoutTypeOrName",
                         `/**
   * @param
   */`);
diff --git a/tests/cases/unittests/transpile.ts b/tests/cases/unittests/transpile.ts
index af275b545c0..d17a7cf93f8 100644
--- a/tests/cases/unittests/transpile.ts
+++ b/tests/cases/unittests/transpile.ts
@@ -64,7 +64,7 @@ namespace ts {
                 it("Correct errors for " + justName, () => {
                     Harness.Baseline.runBaseline("Correct errors", justName.replace(/\.tsx?$/, ".errors.txt"), () => {
                         if (transpileResult.diagnostics.length === 0) {
-                            return null;
+                            return undefined;
                         }
 
                         return Harness.Compiler.getErrorBaseline(toBeCompiled, transpileResult.diagnostics);
@@ -75,7 +75,7 @@ namespace ts {
                     it("Correct errors (old transpile) for " + justName, () => {
                         Harness.Baseline.runBaseline("Correct errors", justName.replace(/\.tsx?$/, ".oldTranspile.errors.txt"), () => {
                             if (oldTranspileDiagnostics.length === 0) {
-                                return null;
+                                return undefined;
                             }
 
                             return Harness.Compiler.getErrorBaseline(toBeCompiled, oldTranspileDiagnostics);