diff --git a/src/cleancss.spec.ts b/src/cleancss.spec.ts
new file mode 100644
index 00000000..7e4700a4
--- /dev/null
+++ b/src/cleancss.spec.ts
@@ -0,0 +1,182 @@
+import { join } from 'path';
+import * as rewire from 'rewire';
+
+const cleanCss = rewire('./cleancss');
+
+import * as cleanCssFactory from './util/clean-css-factory';
+import * as config from './util/config';
+import * as helpers from './util/helpers';
+import * as workerClient from './worker-client';
+
+
+describe('clean css task', () => {
+
+  describe('cleancss', () => {
+    it('should return when the worker returns', async () => {
+      // arrange
+      const context = { };
+      const configFile: any = null;
+      const spy = spyOn(workerClient, workerClient.runWorker.name).and.returnValue(Promise.resolve());
+      // act
+      await (cleanCss as any).cleancss(context, null);
+      // assert
+      expect(spy).toHaveBeenCalledWith('cleancss', 'cleancssWorker', context, configFile);
+    });
+
+    it('should throw when the worker throws', async () => {
+      // arrange
+      const context = { };
+      const errorMessage = 'Simulating an error';
+      spyOn(workerClient, workerClient.runWorker.name).and.throwError(errorMessage);
+      try {
+        // act
+        await (cleanCss as any).cleancss(context, null);
+       throw new Error('Should never get here');
+      } catch (ex) {
+         // assert
+        expect(ex.message).toEqual(errorMessage, `Expected ex.message ${ex.message} to equal ${errorMessage}`);
+      }
+    });
+  });
+
+  describe('cleancssworker', () => {
+    it('should throw when reading the file throws', async (done) => {
+       const errorMessage = 'simulating an error';
+      try {
+        // arrange
+        const context = { buildDir: 'www'};
+        const cleanCssConfig = { sourceFileName: 'sourceFileName', destFileName: 'destFileName'};
+        spyOn(config, config.generateContext.name).and.returnValue(context);
+        spyOn(config, config.fillConfigDefaults.name).and.returnValue(cleanCssConfig);
+        spyOn(helpers, helpers.readFileAsync.name).and.throwError(errorMessage);
+
+        // act
+        await (cleanCss as any).cleancssWorker(context, null);
+
+        throw new Error('Should never get here');
+      } catch (ex) {
+        expect(ex.message).toEqual(errorMessage);
+        done();
+      }
+    });
+
+    it('should return what writeFileAsync returns', async (done) => {
+      // arrange
+      const context = { buildDir: 'www'};
+      const cleanCssConfig = { sourceFileName: 'sourceFileName', destFileName: 'destFileName'};
+      const fileContent = 'content';
+      const minifiedContent = 'someContent';
+      spyOn(config, config.generateContext.name).and.returnValue(context);
+      spyOn(config, config.fillConfigDefaults.name).and.returnValue(cleanCssConfig);
+      spyOn(helpers, helpers.readFileAsync.name).and.returnValue(Promise.resolve(fileContent));
+      spyOn(helpers, helpers.writeFileAsync.name).and.returnValue(Promise.resolve());
+
+      // use rewire to stub this since jasmine is insufficient
+      const spy = jasmine.createSpy('mySpy').and.returnValue(Promise.resolve(minifiedContent));
+      cleanCss.__set__('runCleanCss', spy);
+
+      // act
+      await (cleanCss as any).cleancssWorker(context, null);
+
+      // assert
+      expect(config.generateContext).toHaveBeenCalledWith(context);
+      expect(config.fillConfigDefaults).toHaveBeenCalledWith(null, (cleanCss as any).taskInfo.defaultConfigFile);
+      expect(helpers.readFileAsync).toHaveBeenCalledWith(join(context.buildDir, cleanCssConfig.sourceFileName));
+      expect(helpers.writeFileAsync).toHaveBeenCalledWith(join(context.buildDir, cleanCssConfig.destFileName), minifiedContent);
+      expect(spy).toHaveBeenCalledWith(cleanCssConfig, fileContent);
+      done();
+    });
+  });
+
+  describe('runCleanCss', () => {
+    it('should reject when minification errors out', async (done) => {
+      // arrange
+      const errorMessage = 'simulating an error';
+      const configFile = { options: {} };
+      const fileContent = 'fileContent';
+      let minifySpy: jasmine.Spy = null;
+      try {
+        const destinationFilePath = 'filePath';
+        const mockMinifier = {
+          minify: () => {}
+        };
+        minifySpy = spyOn(mockMinifier, mockMinifier.minify.name);
+        spyOn(cleanCssFactory, cleanCssFactory.getCleanCssInstance.name).and.returnValue(mockMinifier);
+
+        // act
+        const promise = (cleanCss as any).runCleanCss(configFile, fileContent, destinationFilePath);
+        // call the callback from the spy's args
+        const callback = minifySpy.calls.mostRecent().args[1];
+        callback(new Error(errorMessage), null);
+
+        await promise;
+
+        throw new Error('Should never get here');
+      } catch (ex) {
+        // assert
+        expect(ex.message).toEqual(errorMessage);
+        done();
+      }
+    });
+
+    it('should reject when minification has one or more errors', async (done) => {
+      // arrange
+      const configFile = { options: {} };
+      const fileContent = 'fileContent';
+      let minifySpy: jasmine.Spy = null;
+      const minificationResponse = {
+        errors: ['some error']
+      };
+      try {
+        const destinationFilePath = 'filePath';
+        const mockMinifier = {
+          minify: () => {}
+        };
+        minifySpy = spyOn(mockMinifier, mockMinifier.minify.name);
+        spyOn(cleanCssFactory, cleanCssFactory.getCleanCssInstance.name).and.returnValue(mockMinifier);
+
+        // act
+        const promise = (cleanCss as any).runCleanCss(configFile, fileContent, destinationFilePath);
+        // call the callback from the spy's args
+        const callback = minifySpy.calls.mostRecent().args[1];
+        callback(null, minificationResponse);
+
+        await promise;
+
+        throw new Error('Should never get here');
+      } catch (ex) {
+        // assert
+        expect(ex.message).toEqual(minificationResponse.errors[0]);
+        done();
+      }
+    });
+
+    it('should return minified content', async (done) => {
+      const configFile = { options: {} };
+      const fileContent = 'fileContent';
+      let minifySpy: jasmine.Spy = null;
+      const minificationResponse = {
+        styles: 'minifiedContent'
+      };
+      const destinationFilePath = 'filePath';
+      const mockMinifier = {
+        minify: () => {}
+      };
+      minifySpy = spyOn(mockMinifier, mockMinifier.minify.name);
+      spyOn(cleanCssFactory, cleanCssFactory.getCleanCssInstance.name).and.returnValue(mockMinifier);
+
+      // act
+      const promise = (cleanCss as any).runCleanCss(configFile, fileContent, destinationFilePath);
+      // call the callback from the spy's args
+      const callback = minifySpy.calls.mostRecent().args[1];
+      callback(null, minificationResponse);
+
+      const result = await promise;
+      expect(result).toEqual(minificationResponse.styles);
+      expect(cleanCssFactory.getCleanCssInstance).toHaveBeenCalledWith(configFile.options);
+      expect(minifySpy.calls.mostRecent().args[0]).toEqual(fileContent);
+      done();
+    });
+  });
+});
+
diff --git a/src/cleancss.ts b/src/cleancss.ts
index afe743c4..2f4534a0 100644
--- a/src/cleancss.ts
+++ b/src/cleancss.ts
@@ -4,74 +4,59 @@ import { BuildError } from './util/errors';
 import { fillConfigDefaults, generateContext, getUserConfigFile } from './util/config';
 import { Logger } from './logger/logger';
 import { readFileAsync, writeFileAsync } from './util/helpers';
-import { runWorker } from './worker-client';
-import * as cleanCss from 'clean-css';
+import * as workerClient from './worker-client';
+import { CleanCssConfig, getCleanCssInstance } from './util/clean-css-factory';
 
 
-export function cleancss(context: BuildContext, configFile?: string) {
-  configFile = getUserConfigFile(context, taskInfo, configFile);
-
+export async function cleancss(context: BuildContext, configFile?: string) {
   const logger = new Logger('cleancss');
-
-  return runWorker('cleancss', 'cleancssWorker', context, configFile)
-    .then(() => {
-      logger.finish();
-    })
-    .catch(err => {
-      throw logger.fail(err);
-    });
+  try {
+    configFile = getUserConfigFile(context, taskInfo, configFile);
+    await workerClient.runWorker('cleancss', 'cleancssWorker', context, configFile);
+    logger.finish();
+  } catch (ex) {
+    throw logger.fail(ex);
+  }
 }
 
 
-export function cleancssWorker(context: BuildContext, configFile: string): Promise<any> {
-  return new Promise((resolve, reject) => {
-    context = generateContext(context);
-    const cleanCssConfig: CleanCssConfig = fillConfigDefaults(configFile, taskInfo.defaultConfigFile);
-    const srcFile = join(context.buildDir, cleanCssConfig.sourceFileName);
-    const destFile = join(context.buildDir, cleanCssConfig.destFileName);
-
-    Logger.debug(`cleancss read: ${srcFile}`);
-
-    readFileAsync(srcFile).then(fileContent => {
-      const minifier = new cleanCss(cleanCssConfig.options);
-      minifier.minify(fileContent, (err, minified) => {
-        if (err) {
-          reject(new BuildError(err));
-
-        } else if (minified.errors && minified.errors.length > 0) {
-          // just return the first error for now I guess
-          minified.errors.forEach(e => {
-            Logger.error(e);
-          });
-          reject(new BuildError());
+export async function cleancssWorker(context: BuildContext, configFile: string): Promise<any> {
+  context = generateContext(context);
+  const config: CleanCssConfig = fillConfigDefaults(configFile, taskInfo.defaultConfigFile);
+  const srcFile = join(context.buildDir, config.sourceFileName);
+  const destFilePath = join(context.buildDir, config.destFileName);
+  Logger.debug(`[Clean CSS] cleancssWorker: reading source file ${srcFile}`);
+  const fileContent = await readFileAsync(srcFile);
+  const minifiedContent = await runCleanCss(config, fileContent);
+  Logger.debug(`[Clean CSS] runCleanCss: writing file to disk ${destFilePath}`);
+  await writeFileAsync(destFilePath, minifiedContent);
+}
 
-        } else {
-          Logger.debug(`cleancss write: ${destFile}`);
-          writeFileAsync(destFile, minified.styles).then(() => {
-            resolve();
-          });
-        }
-      });
+// exporting for easier unit testing
+export function runCleanCss(cleanCssConfig: CleanCssConfig, fileContent: string): Promise<string> {
+  return new Promise((resolve, reject) => {
+    const minifier = getCleanCssInstance(cleanCssConfig.options);
+    minifier.minify(fileContent, (err, minified) => {
+      if (err) {
+        reject(new BuildError(err));
+      } else if (minified.errors && minified.errors.length > 0) {
+        // just return the first error for now I guess
+        minified.errors.forEach(e => {
+          Logger.error(e);
+        });
+        reject(new BuildError(minified.errors[0]));
+      } else {
+        resolve(minified.styles);
+      }
     });
-
   });
 }
 
-
-const taskInfo: TaskInfo = {
+// export for testing only
+export const taskInfo: TaskInfo = {
   fullArg: '--cleancss',
   shortArg: '-e',
   envVar: 'IONIC_CLEANCSS',
   packageConfig: 'ionic_cleancss',
   defaultConfigFile: 'cleancss.config'
 };
-
-
-export interface CleanCssConfig {
-  // https://www.npmjs.com/package/clean-css
-  sourceFileName: string;
-  // sourceSourceMapName: string;
-  destFileName: string;
-  // options: cleanCss Options;
-  options?: cleanCss.Options;
-}