diff --git a/packages/benchpress/package.json b/packages/benchpress/package.json
index a01e9bcc35..5232c6c52f 100644
--- a/packages/benchpress/package.json
+++ b/packages/benchpress/package.json
@@ -4,6 +4,7 @@
   "description": "Benchpress - a framework for e2e performance tests",
   "main": "index.js",
   "typings": "./index.d.ts",
+  "strictNullChecks": true,
   "dependencies": {
     "@angular/core": "^2.0.0-rc.7",
     "reflect-metadata": "^0.1.2",
diff --git a/packages/benchpress/src/firefox_extension/lib/parser_util.ts b/packages/benchpress/src/firefox_extension/lib/parser_util.ts
index f6a9afedc7..6bccc3c876 100644
--- a/packages/benchpress/src/firefox_extension/lib/parser_util.ts
+++ b/packages/benchpress/src/firefox_extension/lib/parser_util.ts
@@ -16,7 +16,7 @@ export function convertPerfProfileToEvents(perfProfile: any): any[] {
   const finishedEvents: {[key: string]: any}[] = [];  // Event[] finished events
   const addFinishedEvent = function(eventName: string, startTime: number, endTime: number) {
     const categorizedEventName = categorizeEvent(eventName);
-    let args: {[key: string]: any} = undefined;
+    let args: {[key: string]: any}|undefined = undefined;
     if (categorizedEventName == 'gc') {
       // TODO: We cannot measure heap size at the moment
       args = {usedHeapSize: 0};
diff --git a/packages/benchpress/src/metric/perflog_metric.ts b/packages/benchpress/src/metric/perflog_metric.ts
index a3b2bbebfd..391a97ff90 100644
--- a/packages/benchpress/src/metric/perflog_metric.ts
+++ b/packages/benchpress/src/metric/perflog_metric.ts
@@ -140,11 +140,11 @@ export class PerflogMetric extends Metric {
     const markName = this._markName(this._measureCount - 1);
     const nextMarkName = restart ? this._markName(this._measureCount++) : null;
     return this._driverExtension.timeEnd(markName, nextMarkName)
-        .then((_) => this._readUntilEndMark(markName));
+        .then((_: any) => this._readUntilEndMark(markName));
   }
 
   private _readUntilEndMark(
-      markName: string, loopCount: number = 0, startEvent: PerfLogEvent = null) {
+      markName: string, loopCount: number = 0, startEvent: PerfLogEvent|null = null) {
     if (loopCount > _MAX_RETRY_COUNT) {
       throw new Error(`Tried too often to get the ending mark: ${loopCount}`);
     }
@@ -175,7 +175,7 @@ export class PerflogMetric extends Metric {
         }
         startEvent['ph'] = 'B';
         endEvent['ph'] = 'E';
-        endEvent['ts'] = startEvent['ts'] + startEvent['dur'];
+        endEvent['ts'] = startEvent['ts'] ! + startEvent['dur'] !;
         this._remainingEvents.push(startEvent);
         this._remainingEvents.push(endEvent);
       } else {
@@ -185,13 +185,13 @@ export class PerflogMetric extends Metric {
     if (needSort) {
       // Need to sort because of the ph==='X' events
       this._remainingEvents.sort((a, b) => {
-        const diff = a['ts'] - b['ts'];
+        const diff = a['ts'] ! - b['ts'] !;
         return diff > 0 ? 1 : diff < 0 ? -1 : 0;
       });
     }
   }
 
-  private _aggregateEvents(events: PerfLogEvent[], markName: string): {[key: string]: number} {
+  private _aggregateEvents(events: PerfLogEvent[], markName: string): {[key: string]: number}|null {
     const result: {[key: string]: number} = {'scriptTime': 0, 'pureScriptTime': 0};
     if (this._perfLogFeatures.gc) {
       result['gcTime'] = 0;
@@ -217,8 +217,8 @@ export class PerflogMetric extends Metric {
       result['requestCount'] = 0;
     }
 
-    let markStartEvent: PerfLogEvent = null;
-    let markEndEvent: PerfLogEvent = null;
+    let markStartEvent: PerfLogEvent = null !;
+    let markEndEvent: PerfLogEvent = null !;
     events.forEach((event) => {
       const ph = event['ph'];
       const name = event['name'];
@@ -242,8 +242,8 @@ export class PerflogMetric extends Metric {
 
     const frameTimestamps: number[] = [];
     const frameTimes: number[] = [];
-    let frameCaptureStartEvent: PerfLogEvent = null;
-    let frameCaptureEndEvent: PerfLogEvent = null;
+    let frameCaptureStartEvent: PerfLogEvent|null = null;
+    let frameCaptureEndEvent: PerfLogEvent|null = null;
 
     const intervalStarts: {[key: string]: PerfLogEvent} = {};
     const intervalStartCount: {[key: string]: number} = {};
@@ -251,7 +251,7 @@ export class PerflogMetric extends Metric {
     let inMeasureRange = false;
     events.forEach((event) => {
       const ph = event['ph'];
-      let name = event['name'];
+      let name = event['name'] !;
       let microIterations = 1;
       const microIterationsMatch = name.match(_MICRO_ITERATIONS_REGEX);
       if (microIterationsMatch) {
@@ -270,7 +270,7 @@ export class PerflogMetric extends Metric {
       if (this._requestCount && name === 'sendRequest') {
         result['requestCount'] += 1;
       } else if (this._receivedData && name === 'receivedData' && ph === 'I') {
-        result['receivedData'] += event['args']['encodedDataLength'];
+        result['receivedData'] += event['args'] !['encodedDataLength'] !;
       }
       if (ph === 'B' && name === _MARK_NAME_FRAME_CAPTURE) {
         if (frameCaptureStartEvent) {
@@ -289,7 +289,7 @@ export class PerflogMetric extends Metric {
       }
 
       if (ph === 'I' && frameCaptureStartEvent && !frameCaptureEndEvent && name === 'frame') {
-        frameTimestamps.push(event['ts']);
+        frameTimestamps.push(event['ts'] !);
         if (frameTimestamps.length >= 2) {
           frameTimes.push(
               frameTimestamps[frameTimestamps.length - 1] -
@@ -308,14 +308,14 @@ export class PerflogMetric extends Metric {
         intervalStartCount[name]--;
         if (intervalStartCount[name] === 0) {
           const startEvent = intervalStarts[name];
-          const duration = (event['ts'] - startEvent['ts']);
-          intervalStarts[name] = null;
+          const duration = (event['ts'] ! - startEvent['ts'] !);
+          intervalStarts[name] = null !;
           if (name === 'gc') {
             result['gcTime'] += duration;
             const amount =
-                (startEvent['args']['usedHeapSize'] - event['args']['usedHeapSize']) / 1000;
+                (startEvent['args'] !['usedHeapSize'] ! - event['args'] !['usedHeapSize'] !) / 1000;
             result['gcAmount'] += amount;
-            const majorGc = event['args']['majorGc'];
+            const majorGc = event['args'] !['majorGc'];
             if (majorGc && majorGc) {
               result['majorGcTime'] += duration;
             }
diff --git a/packages/benchpress/src/sampler.ts b/packages/benchpress/src/sampler.ts
index 14e7206f58..beb190852c 100644
--- a/packages/benchpress/src/sampler.ts
+++ b/packages/benchpress/src/sampler.ts
@@ -48,7 +48,7 @@ export class Sampler {
   }
 
   private _iterate(lastState: SampleState): Promise<SampleState> {
-    let resultPromise: Promise<SampleState>;
+    let resultPromise: Promise<SampleState|null>;
     if (this._prepare !== Options.NO_PREPARE) {
       resultPromise = this._driver.waitFor(this._prepare);
     } else {
@@ -76,5 +76,5 @@ export class Sampler {
 }
 
 export class SampleState {
-  constructor(public completeSample: MeasureValues[], public validSample: MeasureValues[]) {}
+  constructor(public completeSample: MeasureValues[], public validSample: MeasureValues[]|null) {}
 }
diff --git a/packages/benchpress/src/validator.ts b/packages/benchpress/src/validator.ts
index 9529166cfe..536c22949d 100644
--- a/packages/benchpress/src/validator.ts
+++ b/packages/benchpress/src/validator.ts
@@ -17,7 +17,7 @@ export abstract class Validator {
   /**
    * Calculates a valid sample out of the complete sample
    */
-  validate(completeSample: MeasureValues[]): MeasureValues[] { throw new Error('NYI'); }
+  validate(completeSample: MeasureValues[]): MeasureValues[]|null { throw new Error('NYI'); }
 
   /**
    * Returns a Map that describes the properties of the validator
diff --git a/packages/benchpress/src/validator/regression_slope_validator.ts b/packages/benchpress/src/validator/regression_slope_validator.ts
index ec703ca316..f0e2fa0980 100644
--- a/packages/benchpress/src/validator/regression_slope_validator.ts
+++ b/packages/benchpress/src/validator/regression_slope_validator.ts
@@ -35,7 +35,7 @@ export class RegressionSlopeValidator extends Validator {
     return {'sampleSize': this._sampleSize, 'regressionSlopeMetric': this._metric};
   }
 
-  validate(completeSample: MeasureValues[]): MeasureValues[] {
+  validate(completeSample: MeasureValues[]): MeasureValues[]|null {
     if (completeSample.length >= this._sampleSize) {
       const latestSample =
           completeSample.slice(completeSample.length - this._sampleSize, completeSample.length);
diff --git a/packages/benchpress/src/validator/size_validator.ts b/packages/benchpress/src/validator/size_validator.ts
index ea892da2ac..711eb9edbb 100644
--- a/packages/benchpress/src/validator/size_validator.ts
+++ b/packages/benchpress/src/validator/size_validator.ts
@@ -23,7 +23,7 @@ export class SizeValidator extends Validator {
 
   describe(): {[key: string]: any} { return {'sampleSize': this._sampleSize}; }
 
-  validate(completeSample: MeasureValues[]): MeasureValues[] {
+  validate(completeSample: MeasureValues[]): MeasureValues[]|null {
     if (completeSample.length >= this._sampleSize) {
       return completeSample.slice(completeSample.length - this._sampleSize, completeSample.length);
     } else {
diff --git a/packages/benchpress/src/web_driver_extension.ts b/packages/benchpress/src/web_driver_extension.ts
index ae07ab9aa9..f5d1739763 100644
--- a/packages/benchpress/src/web_driver_extension.ts
+++ b/packages/benchpress/src/web_driver_extension.ts
@@ -43,7 +43,7 @@ export abstract class WebDriverExtension {
       {
         provide: WebDriverExtension,
         useFactory: (children: WebDriverExtension[], capabilities: {[key: string]: any}) => {
-          let delegate: WebDriverExtension;
+          let delegate: WebDriverExtension = undefined !;
           children.forEach(extension => {
             if (extension.supports(capabilities)) {
               delegate = extension;
@@ -64,7 +64,7 @@ export abstract class WebDriverExtension {
 
   timeBegin(name: string): Promise<any> { throw new Error('NYI'); }
 
-  timeEnd(name: string, restartName: string): Promise<any> { throw new Error('NYI'); }
+  timeEnd(name: string, restartName: string|null): Promise<any> { throw new Error('NYI'); }
 
   /**
    * Format:
diff --git a/packages/benchpress/src/webdriver/chrome_driver_extension.ts b/packages/benchpress/src/webdriver/chrome_driver_extension.ts
index 6109ed5b87..bd767bb874 100644
--- a/packages/benchpress/src/webdriver/chrome_driver_extension.ts
+++ b/packages/benchpress/src/webdriver/chrome_driver_extension.ts
@@ -51,7 +51,7 @@ export class ChromeDriverExtension extends WebDriverExtension {
     return this._driver.executeScript(`console.time('${name}');`);
   }
 
-  timeEnd(name: string, restartName: string = null): Promise<any> {
+  timeEnd(name: string, restartName: string|null = null): Promise<any> {
     let script = `console.timeEnd('${name}');`;
     if (restartName) {
       script += `console.time('${restartName}');`;
@@ -82,14 +82,14 @@ export class ChromeDriverExtension extends WebDriverExtension {
   }
 
   private _convertPerfRecordsToEvents(
-      chromeEvents: Array<{[key: string]: any}>, normalizedEvents: PerfLogEvent[] = null) {
+      chromeEvents: Array<{[key: string]: any}>, normalizedEvents: PerfLogEvent[]|null = null) {
     if (!normalizedEvents) {
       normalizedEvents = [];
     }
     chromeEvents.forEach((event) => {
       const categories = this._parseCategories(event['cat']);
       const normalizedEvent = this._convertEvent(event, categories);
-      if (normalizedEvent != null) normalizedEvents.push(normalizedEvent);
+      if (normalizedEvent != null) normalizedEvents !.push(normalizedEvent);
     });
     return normalizedEvents;
   }
@@ -167,7 +167,7 @@ export class ChromeDriverExtension extends WebDriverExtension {
 
   private _isEvent(
       eventCategories: string[], eventName: string, expectedCategories: string[],
-      expectedName: string = null): boolean {
+      expectedName: string|null = null): boolean {
     const hasCategories = expectedCategories.reduce(
         (value, cat) => value && eventCategories.indexOf(cat) !== -1, true);
     return !expectedName ? hasCategories : hasCategories && eventName === expectedName;
diff --git a/packages/benchpress/src/webdriver/firefox_driver_extension.ts b/packages/benchpress/src/webdriver/firefox_driver_extension.ts
index 6dcb8c601c..0c3c360632 100644
--- a/packages/benchpress/src/webdriver/firefox_driver_extension.ts
+++ b/packages/benchpress/src/webdriver/firefox_driver_extension.ts
@@ -32,7 +32,7 @@ export class FirefoxDriverExtension extends WebDriverExtension {
     return this._driver.executeScript('window.markStart("' + name + '");');
   }
 
-  timeEnd(name: string, restartName: string = null): Promise<any> {
+  timeEnd(name: string, restartName: string|null = null): Promise<any> {
     let script = 'window.markEnd("' + name + '");';
     if (restartName != null) {
       script += 'window.markStart("' + restartName + '");';
diff --git a/packages/benchpress/src/webdriver/ios_driver_extension.ts b/packages/benchpress/src/webdriver/ios_driver_extension.ts
index 8557923cb3..8ceb3e2eeb 100644
--- a/packages/benchpress/src/webdriver/ios_driver_extension.ts
+++ b/packages/benchpress/src/webdriver/ios_driver_extension.ts
@@ -23,7 +23,7 @@ export class IOsDriverExtension extends WebDriverExtension {
     return this._driver.executeScript(`console.time('${name}');`);
   }
 
-  timeEnd(name: string, restartName: string = null): Promise<any> {
+  timeEnd(name: string, restartName: string|null = null): Promise<any> {
     let script = `console.timeEnd('${name}');`;
     if (restartName != null) {
       script += `console.time('${restartName}');`;
@@ -50,28 +50,28 @@ export class IOsDriverExtension extends WebDriverExtension {
   }
 
   /** @internal */
-  private _convertPerfRecordsToEvents(records: any[], events: PerfLogEvent[] = null) {
+  private _convertPerfRecordsToEvents(records: any[], events: PerfLogEvent[]|null = null) {
     if (!events) {
       events = [];
     }
     records.forEach((record) => {
-      let endEvent: PerfLogEvent = null;
+      let endEvent: PerfLogEvent|null = null;
       const type = record['type'];
       const data = record['data'];
       const startTime = record['startTime'];
       const endTime = record['endTime'];
 
       if (type === 'FunctionCall' && (data == null || data['scriptName'] !== 'InjectedScript')) {
-        events.push(createStartEvent('script', startTime));
+        events !.push(createStartEvent('script', startTime));
         endEvent = createEndEvent('script', endTime);
       } else if (type === 'Time') {
-        events.push(createMarkStartEvent(data['message'], startTime));
+        events !.push(createMarkStartEvent(data['message'], startTime));
       } else if (type === 'TimeEnd') {
-        events.push(createMarkEndEvent(data['message'], startTime));
+        events !.push(createMarkEndEvent(data['message'], startTime));
       } else if (
           type === 'RecalculateStyles' || type === 'Layout' || type === 'UpdateLayerTree' ||
           type === 'Paint' || type === 'Rasterize' || type === 'CompositeLayers') {
-        events.push(createStartEvent('render', startTime));
+        events !.push(createStartEvent('render', startTime));
         endEvent = createEndEvent('render', endTime);
       }
       // Note: ios used to support GCEvent up until iOS 6 :-(
@@ -79,7 +79,7 @@ export class IOsDriverExtension extends WebDriverExtension {
         this._convertPerfRecordsToEvents(record['children'], events);
       }
       if (endEvent != null) {
-        events.push(endEvent);
+        events !.push(endEvent);
       }
     });
     return events;
diff --git a/packages/benchpress/test/metric/perflog_metric_spec.ts b/packages/benchpress/test/metric/perflog_metric_spec.ts
index 09e71352ba..66b81cc160 100644
--- a/packages/benchpress/test/metric/perflog_metric_spec.ts
+++ b/packages/benchpress/test/metric/perflog_metric_spec.ts
@@ -80,7 +80,7 @@ export function main() {
           sortedKeys(createMetric([[]], new PerfLogFeatures({render: true, gc: false})).describe()))
           .toEqual(['pureScriptTime', 'renderTime', 'scriptTime']);
 
-      expect(sortedKeys(createMetric([[]], null).describe())).toEqual([
+      expect(sortedKeys(createMetric([[]], null !).describe())).toEqual([
         'gcAmount', 'gcTime', 'majorGcTime', 'pureScriptTime', 'renderTime', 'scriptTime'
       ]);
 
@@ -102,7 +102,7 @@ export function main() {
 
     it('should describe itself based on micro metrics', () => {
       const description =
-          createMetric([[]], null, {microMetrics: {'myMicroMetric': 'someDesc'}}).describe();
+          createMetric([[]], null !, {microMetrics: {'myMicroMetric': 'someDesc'}}).describe();
       expect(description['myMicroMetric']).toEqual('someDesc');
     });
 
@@ -130,7 +130,7 @@ export function main() {
 
       it('should not force gc and mark the timeline',
          inject([AsyncTestCompleter], (async: AsyncTestCompleter) => {
-           const metric = createMetric([[]], null);
+           const metric = createMetric([[]], null !);
            metric.beginMeasure().then((_) => {
              expect(commandLog).toEqual([['timeBegin', 'benchpress0']]);
 
@@ -140,7 +140,7 @@ export function main() {
 
       it('should force gc and mark the timeline',
          inject([AsyncTestCompleter], (async: AsyncTestCompleter) => {
-           const metric = createMetric([[]], null, {forceGc: true});
+           const metric = createMetric([[]], null !, {forceGc: true});
            metric.beginMeasure().then((_) => {
              expect(commandLog).toEqual([['gc'], ['timeBegin', 'benchpress0']]);
 
@@ -158,7 +158,7 @@ export function main() {
              eventFactory.markStart('benchpress0', 0), eventFactory.start('script', 4),
              eventFactory.end('script', 6), eventFactory.markEnd('benchpress0', 10)
            ]];
-           const metric = createMetric(events, null);
+           const metric = createMetric(events, null !);
            metric.beginMeasure().then((_) => metric.endMeasure(false)).then((data) => {
              expect(commandLog).toEqual([
                ['timeBegin', 'benchpress0'], ['timeEnd', 'benchpress0', null], 'readPerfLog'
@@ -177,7 +177,7 @@ export function main() {
              eventFactory.start('script', 8), eventFactory.end('script', 9),
              eventFactory.markEnd('benchpress0', 10)
            ]];
-           const metric = createMetric(events, null);
+           const metric = createMetric(events, null !);
            metric.beginMeasure().then((_) => metric.endMeasure(false)).then((data) => {
              expect(data['scriptTime']).toBe(1);
 
@@ -194,7 +194,7 @@ export function main() {
              ],
              [eventFactory.markEnd('benchpress1', 3)]
            ];
-           const metric = createMetric(events, null);
+           const metric = createMetric(events, null !);
            metric.beginMeasure()
                .then((_) => metric.endMeasure(true))
                .then((_) => metric.endMeasure(true))
@@ -218,7 +218,7 @@ export function main() {
                eventFactory.markEnd('benchpress0', 10)
              ]
            ];
-           const metric = createMetric(events, null);
+           const metric = createMetric(events, null !);
            metric.beginMeasure().then((_) => metric.endMeasure(false)).then((data) => {
              expect(commandLog).toEqual([
                ['timeBegin', 'benchpress0'], ['timeEnd', 'benchpress0', null], 'readPerfLog',
@@ -243,7 +243,7 @@ export function main() {
                eventFactory.markEnd('benchpress1', 6)
              ]
            ];
-           const metric = createMetric(events, null);
+           const metric = createMetric(events, null !);
            metric.beginMeasure()
                .then((_) => metric.endMeasure(true))
                .then((data) => {
@@ -275,7 +275,7 @@ export function main() {
         });
 
         it('should measure forced gc', inject([AsyncTestCompleter], (async: AsyncTestCompleter) => {
-             const metric = createMetric(events, null, {forceGc: true});
+             const metric = createMetric(events, null !, {forceGc: true});
              metric.beginMeasure().then((_) => metric.endMeasure(false)).then((data) => {
                expect(commandLog).toEqual([
                  ['gc'], ['timeBegin', 'benchpress0'], ['timeEnd', 'benchpress0', 'benchpress1'],
@@ -290,7 +290,7 @@ export function main() {
 
         it('should restart after the forced gc if needed',
            inject([AsyncTestCompleter], (async: AsyncTestCompleter) => {
-             const metric = createMetric(events, null, {forceGc: true});
+             const metric = createMetric(events, null !, {forceGc: true});
              metric.beginMeasure().then((_) => metric.endMeasure(true)).then((data) => {
                expect(commandLog[5]).toEqual(['timeEnd', 'benchpress1', 'benchpress2']);
 
@@ -312,7 +312,7 @@ export function main() {
       } = {}) {
         events.unshift(eventFactory.markStart('benchpress0', 0));
         events.push(eventFactory.markEnd('benchpress0', 10));
-        const metric = createMetric([events], null, {
+        const metric = createMetric([events], null !, {
           microMetrics: microMetrics,
           captureFrames: captureFrames,
           receivedData: receivedData,
@@ -510,7 +510,7 @@ export function main() {
                  otherProcessEventFactory.end('script', 17, null),
                  eventFactory.markEnd('benchpress0', 20)
                ]],
-               null);
+               null !);
            metric.beginMeasure().then((_) => metric.endMeasure(false)).then((data) => {
              expect(data['scriptTime']).toBe(5);
              async.done();
@@ -674,7 +674,7 @@ class MockDriverExtension extends WebDriverExtension {
     return Promise.resolve(null);
   }
 
-  timeEnd(name: string, restartName: string): Promise<any> {
+  timeEnd(name: string, restartName: string|null): Promise<any> {
     this._commandLog.push(['timeEnd', name, restartName]);
     return Promise.resolve(null);
   }
diff --git a/packages/benchpress/test/reporter/console_reporter_spec.ts b/packages/benchpress/test/reporter/console_reporter_spec.ts
index cc8028233b..bfe30e7547 100644
--- a/packages/benchpress/test/reporter/console_reporter_spec.ts
+++ b/packages/benchpress/test/reporter/console_reporter_spec.ts
@@ -33,7 +33,7 @@ export function main() {
       const providers: Provider[] = [
         ConsoleReporter.PROVIDERS, {
           provide: SampleDescription,
-          useValue: new SampleDescription(sampleId, descriptions, metrics)
+          useValue: new SampleDescription(sampleId, descriptions, metrics !)
         },
         {provide: ConsoleReporter.PRINT, useValue: (line: string) => log.push(line)}
       ];
diff --git a/packages/benchpress/test/runner_spec.ts b/packages/benchpress/test/runner_spec.ts
index 7e56c1aee2..7c4ee88847 100644
--- a/packages/benchpress/test/runner_spec.ts
+++ b/packages/benchpress/test/runner_spec.ts
@@ -15,7 +15,7 @@ export function main() {
     let injector: ReflectiveInjector;
     let runner: Runner;
 
-    function createRunner(defaultProviders: any[] = null): Runner {
+    function createRunner(defaultProviders?: any[]): Runner {
       if (!defaultProviders) {
         defaultProviders = [];
       }
@@ -121,7 +121,7 @@ export function main() {
 
 class MockWebDriverAdapter extends WebDriverAdapter {
   executeScript(script: string): Promise<string> { return Promise.resolve('someUserAgent'); }
-  capabilities(): Promise<Map<string, any>> { return null; }
+  capabilities(): Promise<Map<string, any>> { return null !; }
 }
 
 class MockValidator extends Validator {
@@ -135,6 +135,6 @@ class MockMetric extends Metric {
 }
 
 class MockSampler extends Sampler {
-  constructor() { super(null, null, null, null, null, null, null); }
+  constructor() { super(null !, null !, null !, null !, null !, null !, null !); }
   sample(): Promise<SampleState> { return Promise.resolve(new SampleState([], [])); }
 }
diff --git a/packages/benchpress/test/sampler_spec.ts b/packages/benchpress/test/sampler_spec.ts
index 9d095fd736..e7e8339ee7 100644
--- a/packages/benchpress/test/sampler_spec.ts
+++ b/packages/benchpress/test/sampler_spec.ts
@@ -147,7 +147,7 @@ export function main() {
     it('should call the validator for every execution and store the valid sample',
        inject([AsyncTestCompleter], (async: AsyncTestCompleter) => {
          const log: any[] = [];
-         const validSample = [mv(null, null, {})];
+         const validSample = [mv(null !, null !, {})];
 
          createSampler({
            metric: createCountingMetric(),
@@ -174,7 +174,7 @@ export function main() {
     it('should report the metric values',
        inject([AsyncTestCompleter], (async: AsyncTestCompleter) => {
          const log: any[] = [];
-         const validSample = [mv(null, null, {})];
+         const validSample = [mv(null !, null !, {})];
          createSampler({
            validator: createCountingValidator(2, validSample),
            metric: createCountingMetric(),
@@ -206,8 +206,7 @@ function mv(runIndex: number, time: number, values: {[key: string]: number}) {
   return new MeasureValues(runIndex, new Date(time), values);
 }
 
-function createCountingValidator(
-    count: number, validSample: MeasureValues[] = null, log: any[] = []) {
+function createCountingValidator(count: number, validSample?: MeasureValues[], log: any[] = []) {
   return new MockValidator(log, (completeSample: MeasureValues[]) => {
     count--;
     if (count === 0) {
@@ -224,7 +223,7 @@ function createCountingMetric(log: any[] = []) {
 }
 
 class MockDriverAdapter extends WebDriverAdapter {
-  constructor(private _log: any[] = [], private _waitFor: Function = null) { super(); }
+  constructor(private _log: any[] = [], private _waitFor: Function|null = null) { super(); }
   waitFor(callback: Function): Promise<any> {
     if (this._waitFor != null) {
       return this._waitFor(callback);
@@ -236,7 +235,7 @@ class MockDriverAdapter extends WebDriverAdapter {
 
 
 class MockValidator extends Validator {
-  constructor(private _log: any[] = [], private _validate: Function = null) { super(); }
+  constructor(private _log: any[] = [], private _validate: Function|null = null) { super(); }
   validate(completeSample: MeasureValues[]): MeasureValues[] {
     const stableSample = this._validate != null ? this._validate(completeSample) : completeSample;
     this._log.push(['validate', completeSample, stableSample]);
@@ -245,7 +244,7 @@ class MockValidator extends Validator {
 }
 
 class MockMetric extends Metric {
-  constructor(private _log: any[] = [], private _endMeasure: Function = null) { super(); }
+  constructor(private _log: any[] = [], private _endMeasure: Function|null = null) { super(); }
   beginMeasure() {
     this._log.push(['beginMeasure']);
     return Promise.resolve(null);
diff --git a/packages/benchpress/test/webdriver/chrome_driver_extension_spec.ts b/packages/benchpress/test/webdriver/chrome_driver_extension_spec.ts
index 41ba956469..5cde6cacad 100644
--- a/packages/benchpress/test/webdriver/chrome_driver_extension_spec.ts
+++ b/packages/benchpress/test/webdriver/chrome_driver_extension_spec.ts
@@ -32,7 +32,7 @@ export function main() {
     const normEvents = new TraceEventFactory('timeline', 'pid0');
 
     function createExtension(
-        perfRecords: any[] = null, userAgent: string = null,
+        perfRecords: any[] | null = null, userAgent: string | null = null,
         messageMethod = 'Tracing.dataCollected'): WebDriverExtension {
       if (!perfRecords) {
         perfRecords = [];
@@ -392,7 +392,7 @@ class MockDriverAdapter extends WebDriverAdapter {
     return Promise.resolve(null);
   }
 
-  logs(type: string) {
+  logs(type: string): Promise<any[]> {
     this._log.push(['logs', type]);
     if (type === 'performance') {
       return Promise.resolve(this._events.map(
@@ -401,7 +401,7 @@ class MockDriverAdapter extends WebDriverAdapter {
                 {'message': {'method': this._messageMethod, 'params': event}}, null, 2)
           })));
     } else {
-      return null;
+      return null !;
     }
   }
 }
diff --git a/packages/benchpress/test/webdriver/ios_driver_extension_spec.ts b/packages/benchpress/test/webdriver/ios_driver_extension_spec.ts
index d6661b0ca3..a91fc2982d 100644
--- a/packages/benchpress/test/webdriver/ios_driver_extension_spec.ts
+++ b/packages/benchpress/test/webdriver/ios_driver_extension_spec.ts
@@ -18,7 +18,7 @@ export function main() {
 
     const normEvents = new TraceEventFactory('timeline', 'pid0');
 
-    function createExtension(perfRecords: any[] = null): WebDriverExtension {
+    function createExtension(perfRecords: any[] | null = null): WebDriverExtension {
       if (!perfRecords) {
         perfRecords = [];
       }
@@ -154,7 +154,8 @@ function timeEndRecord(name: string, time: number) {
   return {'type': 'TimeEnd', 'startTime': time, 'data': {'message': name}};
 }
 
-function durationRecord(type: string, startTime: number, endTime: number, children: any[] = null) {
+function durationRecord(
+    type: string, startTime: number, endTime: number, children: any[] | null = null) {
   if (!children) {
     children = [];
   }
@@ -178,7 +179,7 @@ class MockDriverAdapter extends WebDriverAdapter {
     return Promise.resolve(null);
   }
 
-  logs(type: string) {
+  logs(type: string): Promise<any[]> {
     this._log.push(['logs', type]);
     if (type === 'performance') {
       return Promise.resolve(this._perfRecords.map(function(record) {
@@ -189,7 +190,7 @@ class MockDriverAdapter extends WebDriverAdapter {
         };
       }));
     } else {
-      return null;
+      return null !;
     }
   }
 }