diff --git a/test/api/v3/unit/libs/errors.test.js b/test/api/v3/unit/libs/errors.test.js
new file mode 100644
index 0000000000..e859d2bb02
--- /dev/null
+++ b/test/api/v3/unit/libs/errors.test.js
@@ -0,0 +1,94 @@
+import {
+  CustomError,
+  NotAuthorized,
+  BadRequest,
+  InternalServerError,
+} from '../../../../../website/src/libs/api-v3/errors';
+
+describe('Custom Errors', () => {
+  describe('CustomError', () => {
+    it('is an instance of Error', () => {
+      let customError = new CustomError();
+
+      expect(customError).to.be.an.instanceOf(Error);
+    });
+  });
+
+  describe('NotAuthorized', () => {
+    it('is an instance of CustomError', () => {
+      let notAuthorizedError = new NotAuthorized();
+
+      expect(notAuthorizedError).to.be.an.instanceOf(CustomError);
+    });
+
+    it('it returns an http code of 400', () => {
+      let notAuthorizedError = new NotAuthorized();
+
+      expect(notAuthorizedError.httpCode).to.eql(401);
+    });
+
+    it('returns a default message', () => {
+      let notAuthorizedError = new NotAuthorized();
+
+      expect(notAuthorizedError.message).to.eql('Not authorized.');
+    });
+
+    it('allows a custom message', () => {
+      let notAuthorizedError = new NotAuthorized('Custom Error Message');
+
+      expect(notAuthorizedError.message).to.eql('Custom Error Message');
+    });
+  });
+
+  describe('BadRequest', () => {
+    it('is an instance of CustomError', () => {
+      let badRequestError = new BadRequest();
+
+      expect(badRequestError).to.be.an.instanceOf(CustomError);
+    });
+
+    it('it returns an http code of 401', () => {
+      let badRequestError = new BadRequest();
+
+      expect(badRequestError.httpCode).to.eql(400);
+    });
+
+    it('returns a default message', () => {
+      let badRequestError = new BadRequest();
+
+      expect(badRequestError.message).to.eql('Bad request.');
+    });
+
+    it('allows a custom message', () => {
+      let badRequestError = new BadRequest('Custom Error Message');
+
+      expect(badRequestError.message).to.eql('Custom Error Message');
+    });
+  });
+
+  describe('InternalServerError', () => {
+    it('is an instance of CustomError', () => {
+      let internalServerError = new InternalServerError();
+
+      expect(internalServerError).to.be.an.instanceOf(CustomError);
+    });
+
+    it('it returns an http code of 500', () => {
+      let internalServerError = new InternalServerError();
+
+      expect(internalServerError.httpCode).to.eql(500);
+    });
+
+    it('returns a default message', () => {
+      let internalServerError = new InternalServerError();
+
+      expect(internalServerError.message).to.eql('Internal server error.');
+    });
+
+    it('allows a custom message', () => {
+      let internalServerError = new InternalServerError('Custom Error Message');
+
+      expect(internalServerError.message).to.eql('Custom Error Message');
+    });
+  });
+});
diff --git a/test/api/v3/unit/middlewares/errorHandler.test.js b/test/api/v3/unit/middlewares/errorHandler.test.js
new file mode 100644
index 0000000000..39e72b2e45
--- /dev/null
+++ b/test/api/v3/unit/middlewares/errorHandler.test.js
@@ -0,0 +1,77 @@
+import errorHandler from '../../../../../website/src/middlewares/api-v3/errorHandler';
+
+import { BadRequest } from '../../../../../website/src/libs/api-v3/errors';
+import logger from '../../../../../website/src/libs/api-v3/logger';
+
+describe('errorHandler', () => {
+  let res, req;
+
+  beforeEach(() => {
+    res = {
+      status: sinon.stub().returnsThis(),
+      json: sinon.stub(),
+    };
+    req = {
+      originalUrl: 'foo',
+      headers: {},
+      body: {},
+    };
+
+    sinon.stub(logger, 'error');
+  });
+
+  afterEach(() => {
+    logger.error.restore();
+  });
+
+  it('sends internal server error if error is not a CustomError', () => {
+    let error = new Error();
+
+    errorHandler(error, req, res);
+
+    expect(res.status).to.be.calledOnce;
+    expect(res.json).to.be.calledOnce;
+
+    expect(res.status).to.be.calledWith(500);
+    expect(res.json).to.be.calledWith({
+      error: 'InternalServerError',
+      message: 'Internal server error.',
+    });
+  });
+
+  it('sends CustomError', () => {
+    let error = new BadRequest();
+
+    errorHandler(error, req, res);
+
+    expect(res.status).to.be.calledOnce;
+    expect(res.json).to.be.calledOnce;
+
+    expect(res.status).to.be.calledWith(400);
+    expect(res.json).to.be.calledWith({
+      error: 'BadRequest',
+      message: 'Bad request.',
+    });
+  });
+
+  it('logs error', () => {
+    let error = new BadRequest();
+
+    errorHandler(error, req, res);
+
+    expect(logger.error).to.be.calledOnce;
+    expect(logger.error).to.be.calledWith(error.stack, {
+      originalUrl: req.originalUrl,
+      headers: req.headers,
+      body: req.body,
+    });
+  });
+
+  it('does not send error if error is not defined', () => {
+    let next = sinon.stub();
+    errorHandler(null, req, res, next);
+
+    expect(next).to.be.calledOnce;
+    expect(res.status).to.not.be.called;
+  });
+});