diff --git a/frontend/src/services/html-helpers/html-helpers.js b/frontend/src/services/html-helpers/html-helpers.js
index 7956a569c..92d3168b5 100644
--- a/frontend/src/services/html-helpers/html-helpers.js
+++ b/frontend/src/services/html-helpers/html-helpers.js
@@ -11,7 +11,7 @@ export class HtmlHelpers {
       .then(
         (responseText) => {
           const docFrag = document.createRange().createContextualFragment(responseText);
-          let idPrefix;
+          let idPrefix = '';
           if (!options.keepIds) {
             idPrefix = this._getIdPrefix();
             this._prefixIds(docFrag, idPrefix);
diff --git a/frontend/src/services/html-helpers/html-helpers.spec.js b/frontend/src/services/html-helpers/html-helpers.spec.js
index cd13b5cac..c77015b26 100644
--- a/frontend/src/services/html-helpers/html-helpers.spec.js
+++ b/frontend/src/services/html-helpers/html-helpers.spec.js
@@ -2,6 +2,7 @@ import { HtmlHelpers } from "./html-helpers";
 
 describe('HtmlHelpers', () => {
   let htmlHelpers;
+
   beforeEach(() => {
     htmlHelpers = new HtmlHelpers();
   });
@@ -10,13 +11,17 @@ describe('HtmlHelpers', () => {
     expect(htmlHelpers).toBeTruthy();
   });
 
-  describe('parseResponse', () => {
-    it('should return a promise with idPrefix and element', (done) => {
-      const response = {
-        text: () => Promise.resolve('<div>Test</div>'),
-      };
+  describe('parseResponse()', () => {
+    let fakeHttpResponse;
 
-      htmlHelpers.parseResponse(response).then(result => {
+    beforeEach(() => {
+      fakeHttpResponse = {
+        text: () => Promise.resolve('<div id="test-div">Test</div>'),
+      };
+    });
+
+    it('should return a promise with idPrefix and element', (done) => {
+      htmlHelpers.parseResponse(fakeHttpResponse).then(result => {
         expect(result.idPrefix).toBeDefined();
         expect(result.element).toBeDefined();
         expect(result.element.textContent).toMatch('Test');
@@ -25,34 +30,25 @@ describe('HtmlHelpers', () => {
     });
 
     it('should nudge IDs', (done) => {
-      const response = {
-        text: () => Promise.resolve('<div id="test-div">Test</div>'),
-      };
-
-      htmlHelpers.parseResponse(response).then(result => {
+      htmlHelpers.parseResponse(fakeHttpResponse).then(result => {
         expect(result.idPrefix).toBeDefined();
         expect(result.element).toBeDefined();
-        const origElement = result.element.querySelector('#test-div');
-        expect(origElement).toBeFalsy();
-        const nudgedElement = result.element.querySelector('#' + result.idPrefix + 'test-div');
-        expect(nudgedElement).toBeTruthy();
+        const elementWithOrigId = result.element.querySelector('#test-div');
+        expect(elementWithOrigId).toBeFalsy();
+        const elementWithNudgedId = result.element.querySelector('#' + result.idPrefix + 'test-div');
+        expect(elementWithNudgedId).toBeTruthy();
         done();
       });
     });
 
     it('should not nudge IDs with option "keepIds"', (done) => {
-      const response = {
-        text: () => Promise.resolve('<div id="test-div">Test</div>'),
-      };
       const options = { keepIds: true };
 
-      htmlHelpers.parseResponse(response, options).then(result => {
-        expect(result.idPrefix).not.toBeDefined();
+      htmlHelpers.parseResponse(fakeHttpResponse, options).then(result => {
+        expect(result.idPrefix).toBe('');
         expect(result.element).toBeDefined();
-        const origElement = result.element.querySelector('#test-div');
-        expect(origElement).toBeTruthy();
-        const nudgedElement = result.element.querySelector('#' + result.idPrefix + 'test-div');
-        expect(nudgedElement).toBeFalsy();
+        const elementWithOrigId = result.element.querySelector('#test-div');
+        expect(elementWithOrigId).toBeTruthy();
         done();
       });
     });
diff --git a/frontend/src/services/http-client/http-client.spec.js b/frontend/src/services/http-client/http-client.spec.js
new file mode 100644
index 000000000..e61e248f0
--- /dev/null
+++ b/frontend/src/services/http-client/http-client.spec.js
@@ -0,0 +1,116 @@
+import { HttpClient } from "./http-client";
+
+const TEST_URL = 'http://example.com';
+const FAKE_RESPONSE = {
+  data: 'data',
+};
+
+describe('HttpClient', () => {
+  let httpClient;
+
+  beforeEach(() => {
+    httpClient = new HttpClient();
+
+    // setup and spy on fake fetch API
+    spyOn(window, 'fetch').and.returnValue(Promise.resolve(FAKE_RESPONSE));
+  });
+
+  it('should create', () => {
+    expect(httpClient).toBeTruthy();
+  });
+
+  describe('get()', () => {
+    let params;
+
+    beforeEach(() => {
+      params = {
+        url: TEST_URL,
+      };
+    });
+
+    it('should GET the given url', () => {
+      httpClient.get(params);
+      expect(window.fetch).toHaveBeenCalledWith(params.url, jasmine.objectContaining({ method: 'GET' }));
+    });
+
+    it('should return a promise', (done) => {
+      const result = httpClient.get(params);
+      result.then((response) => {
+        expect(response).toEqual(FAKE_RESPONSE);
+        done();
+      });
+    });
+  });
+
+  describe('post()', () => {
+    let params;
+
+    beforeEach(() => {
+      params = {
+        url: TEST_URL,
+      };
+    });
+
+    it('should POST the given url', () => {
+      httpClient.post(params);
+      expect(window.fetch).toHaveBeenCalledWith(params.url, jasmine.objectContaining({ method: 'POST' }));
+    });
+
+    it('should return a promise', (done) => {
+      const result = httpClient.post(params);
+      result.then((response) => {
+        expect(response).toEqual(FAKE_RESPONSE);
+        done();
+      });
+    });
+  });
+
+  describe('Response Interceptors', () => {
+    it('can be added', () => {
+      const interceptor = () => {};
+      expect(httpClient._responseInterceptors.length).toBe(0);
+      httpClient.addResponseInterceptor(interceptor);
+      expect(httpClient._responseInterceptors.length).toBe(1);
+      httpClient.addResponseInterceptor(interceptor);
+      expect(httpClient._responseInterceptors.length).toBe(2);
+    });
+
+    describe('get called', () => {
+      let intercepted1;
+      let intercepted2;
+      const interceptors = {
+        interceptor1: () => intercepted1 = true,
+        interceptor2: () => intercepted2 = true,
+      };
+
+      beforeEach(() => {
+        intercepted1 = false;
+        intercepted2 = false;
+        spyOn(interceptors, 'interceptor1').and.callThrough();
+        spyOn(interceptors, 'interceptor2').and.callThrough();
+        httpClient.addResponseInterceptor(interceptors.interceptor1);
+        httpClient.addResponseInterceptor(interceptors.interceptor2);
+      });
+
+      it('for GET requests', (done) => {
+        httpClient.get({ url: TEST_URL }).then(() => {
+          expect(intercepted1).toBeTruthy();
+          expect(intercepted2).toBeTruthy();
+          expect(interceptors.interceptor1).toHaveBeenCalledWith(FAKE_RESPONSE, jasmine.any(Object));
+          expect(interceptors.interceptor2).toHaveBeenCalledWith(FAKE_RESPONSE, jasmine.any(Object));
+          done();
+        });
+      });
+
+      it('for POST requests', (done) => {
+        httpClient.post({ url: TEST_URL }).then(() => {
+          expect(intercepted1).toBeTruthy();
+          expect(intercepted2).toBeTruthy();
+          expect(interceptors.interceptor1).toHaveBeenCalledWith(FAKE_RESPONSE, jasmine.any(Object));
+          expect(interceptors.interceptor2).toHaveBeenCalledWith(FAKE_RESPONSE, jasmine.any(Object));
+          done();
+        });
+      });
+    });
+  });
+});
diff --git a/frontend/src/services/i18n/i18n.spec.js b/frontend/src/services/i18n/i18n.spec.js
new file mode 100644
index 000000000..76e5348c0
--- /dev/null
+++ b/frontend/src/services/i18n/i18n.spec.js
@@ -0,0 +1,51 @@
+import { I18n } from "./i18n";
+
+describe('I18n', () => {
+  let i18n;
+
+  beforeEach(() => {
+    i18n = new I18n();
+  });
+
+  // helper function
+  function expectTranslation(id, value) {
+    expect(i18n.translations[id]).toMatch(value);
+  }
+
+  it('should create', () => {
+    expect(i18n).toBeTruthy();
+  });
+
+  describe('add()', () => {
+    it('should add the translation', () => {
+      i18n.add('id1', 'translated-id1');
+      expectTranslation('id1', 'translated-id1');
+    });
+  });
+
+  describe('addMany()', () => {
+    it('should add many translations', () => {
+      i18n.addMany({
+        id1: 'translated-id1',
+        id2: 'translated-id2',
+        id3: 'translated-id3',
+      });
+      expectTranslation('id1', 'translated-id1');
+      expectTranslation('id2', 'translated-id2');
+      expectTranslation('id3', 'translated-id3');
+    });
+  });
+
+  describe('get()', () => {
+    it('should return stored translations', () => {
+      i18n.translations.id1 = 'something';
+      expect(i18n.get('id1')).toMatch('something');
+    });
+
+    it('should throw error if translation is missing', () => {
+      expect(() => {
+        i18n.get('id1');
+      }).toThrow();
+    });
+  });
+});
diff --git a/frontend/src/services/util-registry/util-registry.js b/frontend/src/services/util-registry/util-registry.js
index 001bb1e6b..18b656b8c 100644
--- a/frontend/src/services/util-registry/util-registry.js
+++ b/frontend/src/services/util-registry/util-registry.js
@@ -46,10 +46,10 @@ export class UtilRegistry {
   }
 
   setApp(appInstance) {
-    this.appInstance = appInstance;
+    this._appInstance = appInstance;
   }
 
-  setupAll = (scope) => {
+  setupAll(scope) {
     if (DEBUG_MODE > 1) {
       console.info('registered js utilities:');
       console.table(this._registeredUtils);
@@ -70,7 +70,7 @@ export class UtilRegistry {
         let utilInstance = null;
 
         try {
-          utilInstance = util.setup(element, this.appInstance);
+          utilInstance = util.setup(element, this._appInstance);
         } catch(err) {
           if (DEBUG_MODE > 0) {
             console.warn('Error while trying to initialize a utility!', { util , element, err });
diff --git a/frontend/src/services/util-registry/util-registry.spec.js b/frontend/src/services/util-registry/util-registry.spec.js
new file mode 100644
index 000000000..2e4afedf2
--- /dev/null
+++ b/frontend/src/services/util-registry/util-registry.spec.js
@@ -0,0 +1,126 @@
+import { UtilRegistry } from "./util-registry";
+
+const TEST_UTILS = [{
+  name: 'util1',
+  selector: '#some-id',
+  setup: () => {},
+}, {
+  name: 'util2',
+  selector: '[uw-util]',
+  setup: () => {},
+}];
+
+describe('UtilRegistry', () => {
+  let utilRegistry;
+
+  beforeEach(() => {
+    utilRegistry = new UtilRegistry();
+  });
+
+  it('should create', () => {
+    expect(utilRegistry).toBeTruthy();
+  });
+
+  describe('register()', () => {
+    it('should allow to add utilities', () => {
+      utilRegistry.register(TEST_UTILS[0]);
+
+      const foundUtil = utilRegistry.find(TEST_UTILS[0].name);
+      expect(foundUtil).toEqual(TEST_UTILS[0]);
+    });
+  });
+
+  describe('deregister()', () => {
+    it('should remove util', () => {
+      // register util
+      utilRegistry.register(TEST_UTILS[0]);
+      let foundUtil = utilRegistry.find('util1');
+      expect(foundUtil).toBeTruthy();
+
+      // deregister util
+      utilRegistry.deregister(TEST_UTILS[0].name);
+      foundUtil = utilRegistry.find('util1');
+      expect(foundUtil).toBeFalsy();
+    });
+
+    it('should destroy util instances if requested', () => {
+      pending('TBD');
+    });
+  });
+
+  describe('setup()', () => {
+    it('should catch errors thrown by the utility', () => {
+      spyOn(TEST_UTILS[0], 'setup').and.throwError('some error');
+      expect(() => {
+        utilRegistry.setup(TEST_UTILS[0]);
+      }).not.toThrow();
+    });
+
+    it('should pass the app instance', () => {
+      const scope = document.createElement('div');
+      const utilElement = document.createElement('div');
+      utilElement.id = 'some-id';
+      scope.appendChild(utilElement);
+      const fakeApp = { fn: () => {} };
+      utilRegistry.setApp(fakeApp);
+      spyOn(TEST_UTILS[0], 'setup');
+      utilRegistry.setup(TEST_UTILS[0], scope);
+      expect(TEST_UTILS[0].setup).toHaveBeenCalledWith(utilElement, fakeApp);
+    });
+
+    describe('given no scope', () => {
+      it('should use fallback scope', () => {
+        spyOn(TEST_UTILS[0], 'setup');
+        utilRegistry.setup(TEST_UTILS[0]);
+        expect(TEST_UTILS[0].setup).not.toHaveBeenCalled();
+      });
+    });
+
+    describe('given a scope', () => {
+      let scope;
+      let utilElement1;
+      let utilElement2;
+
+      beforeEach(() => {
+        scope = document.createElement('div');
+        utilElement1 = document.createElement('div');
+        utilElement2 = document.createElement('div');
+        utilElement1.setAttribute('uw-util', '');
+        utilElement2.setAttribute('uw-util', '');
+        scope.appendChild(utilElement1);
+        scope.appendChild(utilElement2);
+      });
+
+      it('should call the utilities\' setup function for each matching element', () => {
+        spyOn(TEST_UTILS[1], 'setup');
+        utilRegistry.setup(TEST_UTILS[1], scope);
+        // 2 matching elements in scope
+        expect(TEST_UTILS[1].setup.calls.count()).toBe(2);
+        expect(TEST_UTILS[1].setup.calls.argsFor(0)).toEqual([utilElement1, undefined]);
+        expect(TEST_UTILS[1].setup.calls.argsFor(1)).toEqual([utilElement2, undefined]);
+      });
+    });
+  });
+
+  describe('setupAll()', () => {
+    it('should setup all the utilities', () => {
+      spyOn(utilRegistry, 'setup');
+      utilRegistry.register(TEST_UTILS[0]);
+      utilRegistry.register(TEST_UTILS[1]);
+      utilRegistry.setupAll();
+
+      expect(utilRegistry.setup.calls.count()).toBe(2);
+      expect(utilRegistry.setup.calls.argsFor(0)).toEqual([TEST_UTILS[0], undefined]);
+      expect(utilRegistry.setup.calls.argsFor(1)).toEqual([TEST_UTILS[1], undefined]);
+    });
+
+    it('should pass the given scope', () => {
+      spyOn(utilRegistry, 'setup');
+      utilRegistry.register(TEST_UTILS[0]);
+      const scope = document.createElement('div');
+      utilRegistry.setupAll(scope);
+
+      expect(utilRegistry.setup).toHaveBeenCalledWith(TEST_UTILS[0], scope);
+    });
+  });
+});
diff --git a/package.json b/package.json
index 9b4914798..494be6bb6 100644
--- a/package.json
+++ b/package.json
@@ -15,6 +15,7 @@
     "yesod:test": "./test.sh",
     "frontend:lint": "eslint frontend/src",
     "frontend:test": "karma start --conf karma.conf.js",
+    "frontend:test:watch": "karma start --conf karma.conf.js --single-run false",
     "frontend:build": "webpack",
     "frontend:build:watch": "webpack --watch"
   },