diff --git a/src/api/endpoint/api/publish.ts b/src/api/endpoint/api/publish.ts
index 4191df1cb..0a5ee1a9b 100644
--- a/src/api/endpoint/api/publish.ts
+++ b/src/api/endpoint/api/publish.ts
@@ -14,7 +14,7 @@ import { IAuth, $ResponseExtend, $RequestExtend, $NextFunctionVer, IStorageHandl
 import { logger } from '../../../lib/logger';
 import {isPublishablePackage} from "../../../lib/storage-utils";
 
-export default function publish(router: Router, auth: IAuth, storage: IStorageHandler, config: Config) {
+export default function publish(router: Router, auth: IAuth, storage: IStorageHandler, config: Config): void {
   const can = allow(auth);
 
   /**
@@ -101,9 +101,9 @@ export default function publish(router: Router, auth: IAuth, storage: IStorageHa
 /**
  * Publish a package
  */
-export function publishPackage(storage: IStorageHandler, config: Config, auth: IAuth) {
+export function publishPackage(storage: IStorageHandler, config: Config, auth: IAuth): any {
   const starApi = star(storage);
-  return function(req: $RequestExtend, res: $ResponseExtend, next: $NextFunctionVer) {
+  return function(req: $RequestExtend, res: $ResponseExtend, next: $NextFunctionVer): void {
     const packageName = req.params.package;
 
     logger.debug({packageName} , `publishing or updating a new version for @{packageName}`);
@@ -111,7 +111,7 @@ export function publishPackage(storage: IStorageHandler, config: Config, auth: I
     /**
      * Write tarball of stream data from package clients.
      */
-    const createTarball = function(filename: string, data, cb: Callback) {
+    const createTarball = function(filename: string, data, cb: Callback): void {
       const stream = storage.addTarball(packageName, filename);
       stream.on('error', function(err) {
         cb(err);
@@ -128,18 +128,18 @@ export function publishPackage(storage: IStorageHandler, config: Config, auth: I
     /**
      * Add new package version in storage
      */
-    const createVersion = function(version: string, metadata: Version, cb: Callback) {
+    const createVersion = function(version: string, metadata: Version, cb: Callback): void {
       storage.addVersion(packageName, version, metadata, null, cb);
     };
 
     /**
      * Add new tags in storage
      */
-    const addTags = function(tags: MergeTags, cb: Callback) {
+    const addTags = function(tags: MergeTags, cb: Callback): void  {
       storage.mergeTags(packageName, tags, cb);
     };
 
-    const afterChange = function(error, okMessage, metadata) {
+    const afterChange = function(error, okMessage, metadata): void  {
       const metadataCopy: Package = { ...metadata };
 
       const { _attachments, versions } = metadataCopy;
@@ -218,7 +218,7 @@ export function publishPackage(storage: IStorageHandler, config: Config, auth: I
         logger.debug({packageName} , `updating a new version for @{packageName}`);
         // we check unpublish permissions, an update is basically remove versions
         const remote = req.remote_user;
-        auth.allow_unpublish({packageName}, remote, (error, allowed) => {
+        auth.allow_unpublish({packageName}, remote, (error) => {
           if (error) {
             logger.debug({packageName} , `not allowed to unpublish a version for @{packageName}`);
             return next(error);
@@ -245,7 +245,7 @@ export function publishPackage(storage: IStorageHandler, config: Config, auth: I
  * un-publish a package
  */
 export function unPublishPackage(storage: IStorageHandler) {
-  return function(req: $RequestExtend, res: $ResponseExtend, next: $NextFunctionVer) {
+  return function(req: $RequestExtend, res: $ResponseExtend, next: $NextFunctionVer): void {
     const packageName = req.params.package;
 
     logger.debug({packageName} , `unpublishing @{packageName}`);
@@ -263,7 +263,7 @@ export function unPublishPackage(storage: IStorageHandler) {
  * Delete tarball
  */
 export function removeTarball(storage: IStorageHandler) {
-  return function(req: $RequestExtend, res: $ResponseExtend, next: $NextFunctionVer) {
+  return function(req: $RequestExtend, res: $ResponseExtend, next: $NextFunctionVer): void {
     const packageName = req.params.package;
     const {filename, revision} = req.params;
 
@@ -283,7 +283,7 @@ export function removeTarball(storage: IStorageHandler) {
  * Adds a new version
  */
 export function addVersion(storage: IStorageHandler) {
-  return function(req: $RequestExtend, res: $ResponseExtend, next: $NextFunctionVer) {
+  return function(req: $RequestExtend, res: $ResponseExtend, next: $NextFunctionVer): void {
     const { version, tag } = req.params;
     const packageName = req.params.package;
 
diff --git a/src/lib/config-path.ts b/src/lib/config-path.ts
index f401e50eb..2d1cc8f2c 100644
--- a/src/lib/config-path.ts
+++ b/src/lib/config-path.ts
@@ -1,8 +1,3 @@
-/**
- * @prettier
- * @flow
- */
-
 import fs from 'fs';
 import _ from 'lodash';
 import Path from 'path';
@@ -16,18 +11,24 @@ const CONFIG_FILE = 'config.yaml';
 const XDG = 'xdg';
 const WIN = 'win';
 const WIN32 = 'win32';
+// eslint-disable-next-line
 const pkgJSON = require('../../package.json');
 
+export type SetupDirectory = {
+  path: string;
+  type: string
+};
+
 /**
  * Find and get the first config file that match.
  * @return {String} the config file path
  */
-function findConfigFile(configPath: any) {
+function findConfigFile(configPath: string): string {
   if (_.isNil(configPath) === false) {
     return Path.resolve(configPath);
   }
 
-  const configPaths = getConfigPaths();
+  const configPaths: SetupDirectory[] = getConfigPaths();
 
   if (_.isEmpty(configPaths)) {
     throw new Error('no configuration files can be processed');
@@ -41,7 +42,7 @@ function findConfigFile(configPath: any) {
   return createConfigFile(_.head(configPaths)).path;
 }
 
-function createConfigFile(configLocation: any) {
+function createConfigFile(configLocation: any): SetupDirectory {
   createConfigFolder(configLocation);
 
   const defaultConfig = updateStorageLinks(configLocation, readDefaultConfig());
@@ -51,16 +52,16 @@ function createConfigFile(configLocation: any) {
   return configLocation;
 }
 
-function readDefaultConfig() {
+function readDefaultConfig(): string {
   return fs.readFileSync(require.resolve('../../conf/default.yaml'), CHARACTER_ENCODING.UTF8);
 }
 
-function createConfigFolder(configLocation) {
+function createConfigFolder(configLocation): void {
   mkdirp.sync(Path.dirname(configLocation.path));
   logger.info({ file: configLocation.path }, 'Creating default config file in @{file}');
 }
 
-function updateStorageLinks(configLocation, defaultConfig) {
+function updateStorageLinks(configLocation, defaultConfig): string {
   if (configLocation.type !== XDG) {
     return defaultConfig;
   }
@@ -77,13 +78,19 @@ function updateStorageLinks(configLocation, defaultConfig) {
   }
 }
 
-function getConfigPaths() {
-  return [getXDGDirectory(), getWindowsDirectory(), getRelativeDefaultDirectory(), getOldDirectory()].filter(
-    path => !!path
-  );
+function getConfigPaths(): SetupDirectory[] {
+  const listPaths: SetupDirectory[] = [getXDGDirectory(), getWindowsDirectory(), getRelativeDefaultDirectory(), getOldDirectory()].reduce(
+    function(acc, currentValue: any): SetupDirectory[] {
+      if (_.isUndefined(currentValue) === false) {
+        acc.push(currentValue);
+      }
+      return acc;
+    }, [] as SetupDirectory[]);
+
+  return listPaths;
 }
 
-const getXDGDirectory = () => {
+const getXDGDirectory = (): SetupDirectory | void => {
   const XDGConfig = getXDGHome() || (process.env.HOME && Path.join(process.env.HOME, '.config'));
 
   if (XDGConfig && folderExists(XDGConfig)) {
@@ -94,9 +101,9 @@ const getXDGDirectory = () => {
   }
 };
 
-const getXDGHome = () => process.env.XDG_CONFIG_HOME;
+const getXDGHome = (): string | void => process.env.XDG_CONFIG_HOME;
 
-const getWindowsDirectory = () => {
+const getWindowsDirectory = (): SetupDirectory | void => {
   if (process.platform === WIN32 && process.env.APPDATA && folderExists(process.env.APPDATA)) {
     return {
       path: Path.resolve(Path.join(process.env.APPDATA, pkgJSON.name, CONFIG_FILE)),
@@ -105,14 +112,14 @@ const getWindowsDirectory = () => {
   }
 };
 
-const getRelativeDefaultDirectory = () => {
+const getRelativeDefaultDirectory = (): SetupDirectory => {
   return {
     path: Path.resolve(Path.join('.', pkgJSON.name, CONFIG_FILE)),
     type: 'def',
   };
 };
 
-const getOldDirectory = () => {
+const getOldDirectory = (): SetupDirectory => {
   return {
     path: Path.resolve(Path.join('.', CONFIG_FILE)),
     type: 'old',
diff --git a/src/lib/crypto-utils.ts b/src/lib/crypto-utils.ts
index 11df4ecef..de522de42 100644
--- a/src/lib/crypto-utils.ts
+++ b/src/lib/crypto-utils.ts
@@ -1,4 +1,4 @@
-import { createDecipher, createCipher, createHash, pseudoRandomBytes } from 'crypto';
+import { createDecipher, createCipher, createHash, pseudoRandomBytes, Hash } from 'crypto';
 import jwt from 'jsonwebtoken';
 
 import { JWTSignOptions, RemoteUser } from '@verdaccio/types';
@@ -16,7 +16,7 @@ export function aesEncrypt(buf: Buffer, secret: string): Buffer {
   return Buffer.concat([b1, b2]);
 }
 
-export function aesDecrypt(buf: Buffer, secret: string) {
+export function aesDecrypt(buf: Buffer, secret: string): Buffer {
   try {
     // deprecated (it will be migrated in Verdaccio 5), it is a breaking change
     // https://nodejs.org/api/crypto.html#crypto_crypto_createdecipher_algorithm_password_options
@@ -30,7 +30,7 @@ export function aesDecrypt(buf: Buffer, secret: string) {
   }
 }
 
-export function createTarballHash() {
+export function createTarballHash(): Hash {
   return createHash(defaultTarballHashAlgorithm);
 }
 
@@ -47,12 +47,12 @@ export function stringToMD5(data: Buffer | string): string {
     .digest('hex');
 }
 
-export function generateRandomHexString(length: number = 8) {
+export function generateRandomHexString(length = 8): string {
   return pseudoRandomBytes(length).toString('hex');
 }
 
 export async function signPayload(payload: RemoteUser, secretOrPrivateKey: string, options: JWTSignOptions): Promise<string> {
-  return new Promise(function(resolve, reject) {
+  return new Promise(function(resolve, reject): Promise<string> {
     return jwt.sign(
       payload,
       secretOrPrivateKey,
@@ -65,6 +65,6 @@ export async function signPayload(payload: RemoteUser, secretOrPrivateKey: strin
   });
 }
 
-export function verifyPayload(token: string, secretOrPrivateKey: string) {
+export function verifyPayload(token: string, secretOrPrivateKey: string): RemoteUser {
   return jwt.verify(token, secretOrPrivateKey);
 }
diff --git a/src/lib/utils.ts b/src/lib/utils.ts
index b05418008..179c2ec84 100644
--- a/src/lib/utils.ts
+++ b/src/lib/utils.ts
@@ -38,8 +38,11 @@ import {
 } from '@verdaccio/commons-api';
 import { IncomingHttpHeaders } from 'http2';
 
-const Logger = require('./logger');
-const pkginfo = require('pkginfo')(module); // eslint-disable-line no-unused-vars
+import { logger } from './logger';
+
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
+// eslint-disable-next-line @typescript-eslint/no-var-requires
+require('pkginfo')(module);
 const pkgVersion = module.exports.version;
 const pkgName = module.exports.name;
 
@@ -287,7 +290,7 @@ export function semverSort(listVersions: string[]): string[] {
     listVersions
       .filter(function(x): boolean {
         if (!semver.parse(x, true)) {
-          Logger.logger.warn({ ver: x }, 'ignoring bad version @{ver}');
+          logger.warn({ ver: x }, 'ignoring bad version @{ver}');
           return false;
         }
         return true;
@@ -525,7 +528,7 @@ export function parseReadme(packageName: string, readme: string): string | void
   }
 
   // logs readme not found error
-  Logger.logger.error({ packageName }, '@{packageName}: No readme found');
+  logger.error({ packageName }, '@{packageName}: No readme found');
 
   return sanitizyReadme('ERROR: No README data found!');
 }
@@ -606,15 +609,15 @@ export function pad(str, max): string {
  * @param {Number} charNum
  * @returns {String}
  */
-export function mask(str: string, charNum = 3) {
+export function mask(str: string, charNum = 3): string {
   return `${str.substr(0, charNum)}...${str.substr(-charNum)}`;
 }
 
-export function encodeScopedUri(packageName) {
+export function encodeScopedUri(packageName): string {
   return packageName.replace(/\//g, '%2f');
 }
 
-export function hasDiffOneKey(versions) {
+export function hasDiffOneKey(versions): boolean {
   return Object.keys(versions).length !== 1;
 }
 
diff --git a/test/e2e/.eslintrc b/test/e2e/.eslintrc
new file mode 100644
index 000000000..cbfb89d2f
--- /dev/null
+++ b/test/e2e/.eslintrc
@@ -0,0 +1,6 @@
+{
+  "rules": {
+    "@typescript-eslint/no-var-requires": 0,
+    "@typescript-eslint/explicit-member-accessibility": 0
+  }
+}
diff --git a/test/functional/fixtures/plugins/middlewares.es6.js b/test/functional/fixtures/plugins/middlewares.es6.js
index e6893e6d1..0d17e46a3 100644
--- a/test/functional/fixtures/plugins/middlewares.es6.js
+++ b/test/functional/fixtures/plugins/middlewares.es6.js
@@ -1,3 +1,5 @@
+/* eslint-disable @typescript-eslint/explicit-member-accessibility */
+
 /**
  * Original plugin in ES6
  *
@@ -34,9 +36,10 @@ class PluginES6 {
 
   constructor(config, stuff) {
     this._config = config;
+    this._logger = stuff.logger;
   }
 
-  register_middlewares(app, auth, storage) {
+  register_middlewares(app, /* auth, storage */) {
     const message = this._config.message;
 
 
diff --git a/test/functional/fixtures/plugins/middlewares.js b/test/functional/fixtures/plugins/middlewares.js
index 8a6f11500..cdeee39ce 100644
--- a/test/functional/fixtures/plugins/middlewares.js
+++ b/test/functional/fixtures/plugins/middlewares.js
@@ -1,11 +1,12 @@
-function Plugin(config, stuff) {
+function Plugin(config, pluginOptions) {
   const self = Object.create(Plugin.prototype);
 
   self._config = config;
+  self._logger = pluginOptions.logger;
   return self;
 }
 
-Plugin.prototype.register_middlewares = function (app, auth, storage) {
+Plugin.prototype.register_middlewares = function (app) {
 
   const {message} = this._config;
   app.get('/test/route', function (req, res, next) {
@@ -13,7 +14,6 @@ Plugin.prototype.register_middlewares = function (app, auth, storage) {
 
     return next({ ok: message })
   });
-
-}
+};
 
 module.exports = Plugin;
diff --git a/test/functional/fixtures/plugins/middlewares.uplink.js b/test/functional/fixtures/plugins/middlewares.uplink.js
index ff8d3a4ad..24381eaf9 100644
--- a/test/functional/fixtures/plugins/middlewares.uplink.js
+++ b/test/functional/fixtures/plugins/middlewares.uplink.js
@@ -1,3 +1,4 @@
+/* eslint-disable @typescript-eslint/no-var-requires */
 const nock = require('nock');
 
 function Plugin(config) {
@@ -6,13 +7,14 @@ function Plugin(config) {
   return self;
 }
 
-Plugin.prototype.register_middlewares = function (app, auth, storage) {
+Plugin.prototype.register_middlewares = function (app) {
 
   app.get('/test-uplink-timeout-*', function (req, res, next) {
     // https://github.com/nock/nock#readme
     nock('http://localhost:55552')
       .get(req.path)
-      // 31s is greater than the default 30s connection timeout
+      // note: we use 50s due hardware reasons small threshold is not enough to make fails
+      // 50s is greater than the default 30s connection timeout
       .socketDelay(50000)
       // http-status 200 OK
       .reply(200);
diff --git a/test/functional/lib/simple_server.ts b/test/functional/lib/simple_server.ts
index 3daf6b266..2fc91d38b 100644
--- a/test/functional/lib/simple_server.ts
+++ b/test/functional/lib/simple_server.ts
@@ -1,24 +1,36 @@
 import express from 'express';
 import bodyParser from 'body-parser';
 
+/**
+ * Simple Server
+ *
+ * A emtpy express server with the objetive to emumate any external API.
+ *
+ * eg: test/functional/tags/tags.ts
+ *
+ *  express.get('/testexp_tags', function(req, res) {
+        let f = readTags().toString().replace(/__NAME__/g, 'testexp_tags');
+        res.send(JSON.parse(f));
+    });
+ *
+ * or at test/functional/package/gzip.ts
+ */
 export default class ExpressServer {
-  app: any;
-  server: any;
+  private app: any;
+  private server: any;
 
-  constructor() {
+  public constructor() {
     this.app = express();
   }
 
-  start(port: number): Promise<any> {
+  public start(port: number): Promise<ExpressServer> {
     return new Promise((resolve) => {
       this.app.use(bodyParser.json());
       this.app.use(bodyParser.urlencoded({
         extended: true
       }));
 
-      this.server = this.app.listen(port, () => {
-        resolve(this);
-      });
+      this.server = this.app.listen(port, () => resolve(this));
     });
   }
 }
diff --git a/test/functional/pre-setup.js b/test/functional/pre-setup.js
index 8be36bcba..19decbf84 100644
--- a/test/functional/pre-setup.js
+++ b/test/functional/pre-setup.js
@@ -1,3 +1,5 @@
+/* eslint-disable @typescript-eslint/no-var-requires */
+
 require('@babel/register')({
   extensions: [".ts", ".js"]
 });
diff --git a/test/functional/readme/readme.ts b/test/functional/readme/readme.ts
index 61cfbdeaa..7619182a9 100644
--- a/test/functional/readme/readme.ts
+++ b/test/functional/readme/readme.ts
@@ -1,5 +1,8 @@
 import {DEFAULT_NO_README, HTTP_STATUS} from '../../../src/lib/constants';
 
+import pkgReadmeJSON from './pkg-readme.json';
+import pkgNoReadmeJSON from './pkg-no-readme.json';
+
 export default function (server, server2) {
 
   describe('should test readme', () => {
@@ -8,9 +11,9 @@ export default function (server, server2) {
     const README_MESSAGE = 'this is a readme';
 
     beforeAll(async function() {
-      await server.putPackage('readme-test', require('./pkg-readme.json'))
+      await server.putPackage('readme-test', pkgReadmeJSON)
         .status(HTTP_STATUS.CREATED);
-      await server.putPackage(README_PKG2, require('./pkg-no-readme.json'))
+      await server.putPackage(README_PKG2, pkgNoReadmeJSON)
         .status(HTTP_STATUS.CREATED);
     });
 
diff --git a/test/functional/search/simple.search.ts b/test/functional/search/simple.search.ts
index 51cd250d9..0ddfb09d3 100644
--- a/test/functional/search/simple.search.ts
+++ b/test/functional/search/simple.search.ts
@@ -1,6 +1,5 @@
 import {API_MESSAGE, HTTP_STATUS} from '../../../src/lib/constants';
-
-const pkgExample = require('./search.json');
+import pkgExample from './search.json';
 
 export default function(server, server2, express) {
 
diff --git a/test/functional/tags/dist-tags-merge.ts b/test/functional/tags/dist-tags-merge.ts
index ebd34291f..45c58b2c7 100644
--- a/test/functional/tags/dist-tags-merge.ts
+++ b/test/functional/tags/dist-tags-merge.ts
@@ -2,9 +2,7 @@ import {generateSha} from '../lib/test.utils';
 import {API_MESSAGE, HTTP_STATUS} from '../../../src/lib/constants';
 import {DOMAIN_SERVERS, PORT_SERVER_1, PORT_SERVER_2, PORT_SERVER_3} from '../config.functional';
 import {DIST_TAGS} from '../../../src/lib/constants';
-
-
-const pkgExample = require('./dist-tags-merge.json');
+import pkgExample from './dist-tags-merge.json';
 
 export default function(server, server2, server3) {
 
diff --git a/test/functional/test-environment.js b/test/functional/test-environment.js
index fdbfc6eb6..4f37edfd8 100644
--- a/test/functional/test-environment.js
+++ b/test/functional/test-environment.js
@@ -1,3 +1,5 @@
+/* eslint-disable @typescript-eslint/no-var-requires */
+
 require('@babel/register')({
   extensions: [".ts", ".js"]
 });
diff --git a/test/lib/helper/register.js b/test/lib/helper/register.js
index c38e35351..0c0f6e597 100644
--- a/test/lib/helper/register.js
+++ b/test/lib/helper/register.js
@@ -1,3 +1,5 @@
+/* eslint-disable @typescript-eslint/no-var-requires */
+
 require('@babel/register')({
   sourceMap: 'inline',
 });
diff --git a/test/lib/server.ts b/test/lib/server.ts
index a79f7e24a..79e21494d 100644
--- a/test/lib/server.ts
+++ b/test/lib/server.ts
@@ -148,19 +148,20 @@ export default class Server implements IServerBridge {
     }).send(JSON.stringify(version));
   }
 
-  public putTarballIncomplete(name: string, filename: string, data: any, size: number, cb: Function): Promise<any> {
+  public putTarballIncomplete(pkgName: string, filename: string, data: any, headerContentSize: number): Promise<any> {
     let promise = this.request({
-      uri: `/${encodeURIComponent(name)}/-/${encodeURIComponent(filename)}/whatever`,
+      uri: `/${encodeURIComponent(pkgName)}/-/${encodeURIComponent(filename)}/whatever`,
       method: 'PUT',
       headers: {
         [HEADERS.CONTENT_TYPE]: HEADERS.OCTET_STREAM,
-        [HEADERS.CONTENT_LENGTH]: size,
+        [HEADERS.CONTENT_LENGTH]: headerContentSize,
       },
       timeout: 1000,
     });
 
     promise.request(function(req) {
       req.write(data);
+      // it auto abort the request
       setTimeout(function() {
         req.req.abort();
       }, 20);
diff --git a/test/lib/server_process.ts b/test/lib/server_process.ts
index a58fa00f7..6e264558b 100644
--- a/test/lib/server_process.ts
+++ b/test/lib/server_process.ts
@@ -8,18 +8,18 @@ import {IVerdaccioConfig, IServerBridge, IServerProcess} from '../types';
 
 export default class VerdaccioProcess implements IServerProcess {
 
-  bridge: IServerBridge;
-  config: IVerdaccioConfig;
-  childFork: any;
-  isDebug: boolean;
-  silence: boolean;
-  cleanStore: boolean;
+  private bridge: IServerBridge;
+  private config: IVerdaccioConfig;
+  private childFork: any;
+  private isDebug: boolean;
+  private silence: boolean;
+  private cleanStore: boolean;
 
   public constructor(config: IVerdaccioConfig,
     bridge: IServerBridge,
-    silence: boolean = true,
-    isDebug: boolean = false,
-    cleanStore: boolean = true) {
+    silence = true,
+    isDebug = false,
+    cleanStore = true) {
     this.config = config;
     this.bridge = bridge;
     this.silence = silence;
@@ -27,7 +27,7 @@ export default class VerdaccioProcess implements IServerProcess {
     this.cleanStore = cleanStore;
   }
 
-  public init(verdaccioPath: string = '../../bin/verdaccio'): Promise<any> {
+  public init(verdaccioPath = '../../bin/verdaccio'): Promise<any> {
     return new Promise((resolve, reject) => {
       if(this.cleanStore) {
         rimRaf(this.config.storagePath, (err) => {
diff --git a/test/lib/utils-test.ts b/test/lib/utils-test.ts
index 1345087c7..bb532c223 100644
--- a/test/lib/utils-test.ts
+++ b/test/lib/utils-test.ts
@@ -3,7 +3,7 @@ import { Version } from "@verdaccio/types";
 export function generateNewVersion(
   pkgName: string,
   version: string,
-  shashum: string = '238e7641e59508dc9c20eb4ad37a8aa57ab777b4'): Version {
+  shashum = '238e7641e59508dc9c20eb4ad37a8aa57ab777b4'): Version {
   // $FlowFixMe
   return {
     "name": pkgName,
diff --git a/test/lib/verdaccio-server.ts b/test/lib/verdaccio-server.ts
index d1d8930ac..c4ea6e1ce 100644
--- a/test/lib/verdaccio-server.ts
+++ b/test/lib/verdaccio-server.ts
@@ -7,7 +7,7 @@ export class VerdaccioConfig implements IVerdaccioConfig {
   public domainPath: string;
   public port: number;
 
-  constructor(storagePath: string, configPath: string, domainPath: string, port: number) {
+  public constructor(storagePath: string, configPath: string, domainPath: string, port: number) {
     this.storagePath = storagePath;
     this.configPath = configPath;
     this.domainPath = domainPath;
diff --git a/test/types-test/.eslintrc b/test/types-test/.eslintrc
new file mode 100644
index 000000000..6f5f938c4
--- /dev/null
+++ b/test/types-test/.eslintrc
@@ -0,0 +1,5 @@
+{
+  "rules": {
+    "@typescript-eslint/explicit-member-accessibility": 0
+  }
+}
diff --git a/test/types-test/README.md b/test/types-test/README.md
new file mode 100644
index 000000000..e131b4a15
--- /dev/null
+++ b/test/types-test/README.md
@@ -0,0 +1,7 @@
+# Types smoke test
+
+This folder is intended to check whether any type update might break plugin implementations
+
+## Contribute
+
+- Add more scenarios, middleware, plugins, filters etc.
\ No newline at end of file
diff --git a/test/flow/plugins/auth/example.auth.plugin.js b/test/types-test/plugins/auth/example.auth.plugin.ts
similarity index 60%
rename from test/flow/plugins/auth/example.auth.plugin.js
rename to test/types-test/plugins/auth/example.auth.plugin.ts
index 6d92587aa..b846da6d3 100644
--- a/test/flow/plugins/auth/example.auth.plugin.js
+++ b/test/types-test/plugins/auth/example.auth.plugin.ts
@@ -1,42 +1,37 @@
-/**
- * @prettier
- */
-
-// @flow
-
 // this file is not aim to be tested, just to check flow definitions
 
 import Config from '../../../../src/lib/config';
-import LoggerApi from '../../../../src/lib/logger';
+import { logger } from '../../../../src/lib/logger';
+import { Callback } from '@verdaccio/types';
 
 import { Config as AppConfig, PackageAccess, IPluginAuth, RemoteUser, Logger, PluginOptions } from '@verdaccio/types';
 
-class ExampleAuthPlugin implements IPluginAuth {
+class ExampleAuthPlugin implements IPluginAuth<{}> {
   config: AppConfig;
   logger: Logger;
 
-  constructor(config: AppConfig, options: PluginOptions) {
+  constructor(config: AppConfig, options: PluginOptions<{}>) {
     this.config = config;
     this.logger = options.logger;
   }
 
-  adduser(user: string, password: string, cb: verdaccio$Callback): void {
+  adduser(user: string, password: string, cb: Callback): void {
     cb();
   }
 
-  changePassword(username, password, newPassword, cb: verdaccio$Callback): void {
+  changePassword(username, password, newPassword, cb: Callback): void {
     cb();
   }
 
-  authenticate(user: string, password: string, cb: verdaccio$Callback): void {
+  authenticate(user: string, password: string, cb: Callback): void {
     cb();
   }
 
-  allow_access(user: RemoteUser, pkg: PackageAccess, cb: verdaccio$Callback): void {
+  allow_access(user: RemoteUser, pkg: PackageAccess, cb: Callback): void {
     cb();
   }
 
-  allow_publish(user: RemoteUser, pkg: PackageAccess, cb: verdaccio$Callback): void {
+  allow_publish(user: RemoteUser, pkg: PackageAccess, cb: Callback): void {
     cb();
   }
 }
@@ -45,32 +40,32 @@ type SubTypePackageAccess = PackageAccess & {
   sub?: boolean;
 };
 
-class ExampleAuthCustomPlugin implements IPluginAuth {
+class ExampleAuthCustomPlugin implements IPluginAuth<{}> {
   config: AppConfig;
   logger: Logger;
 
-  constructor(config: AppConfig, options: PluginOptions) {
+  constructor(config: AppConfig, options: PluginOptions<{}>) {
     this.config = config;
     this.logger = options.logger;
   }
 
-  adduser(user: string, password: string, cb: verdaccio$Callback): void {
+  adduser(user: string, password: string, cb: Callback): void {
     cb();
   }
 
-  changePassword(username, password, newPassword, cb: verdaccio$Callback): void {
+  changePassword(username, password, newPassword, cb: Callback): void {
     cb();
   }
 
-  authenticate(user: string, password: string, cb: verdaccio$Callback): void {
+  authenticate(user: string, password: string, cb: Callback): void {
     cb();
   }
 
-  allow_access(user: RemoteUser, pkg: SubTypePackageAccess, cb: verdaccio$Callback): void {
+  allow_access(user: RemoteUser, pkg: SubTypePackageAccess, cb: Callback): void {
     cb();
   }
 
-  allow_publish(user: RemoteUser, pkg: SubTypePackageAccess, cb: verdaccio$Callback): void {
+  allow_publish(user: RemoteUser, pkg: SubTypePackageAccess, cb: Callback): void {
     cb();
   }
 }
@@ -80,9 +75,9 @@ const config1: AppConfig = new Config({
   self_path: '/home/sotrage',
 });
 
-const options: PluginOptions = {
+const options: PluginOptions<{}> = {
   config: config1,
-  logger: LoggerApi.logger.child(),
+  logger: logger.child(),
 };
 
 const auth = new ExampleAuthPlugin(config1, options);
diff --git a/test/flow/plugins/middleware/example.middleware.plugin.js b/test/types-test/plugins/middleware/example.middleware.plugin.ts
similarity index 65%
rename from test/flow/plugins/middleware/example.middleware.plugin.js
rename to test/types-test/plugins/middleware/example.middleware.plugin.ts
index 4d8c41f88..075107e74 100644
--- a/test/flow/plugins/middleware/example.middleware.plugin.js
+++ b/test/types-test/plugins/middleware/example.middleware.plugin.ts
@@ -1,11 +1,13 @@
-// @flow
+// this file is not aim to be tested, just to check typescript definitions
+/* eslint-disable @typescript-eslint/no-unused-vars */
+/* eslint-disable no-unused-vars */
 
-// this file is not aim to be tested, just to check flow definitions
 import Config from '../../../../src/lib/config';
 import {generatePackageTemplate} from '../../../../src/lib/storage-utils';
 import {readFile} from '../../../functional/lib/test.utils';
+import { Package } from '@verdaccio/types';
 
-const readMetadata = (fileName: string = 'metadata') => readFile(`../../unit/partials/${fileName}`);
+const readMetadata = (fileName: string): Package => JSON.parse(readFile(`../../unit/partials/${fileName}`).toString()) as Package;
 
 import {
   Config as AppConfig,
@@ -15,9 +17,10 @@ import {
   IBasicAuth,
 } from '@verdaccio/types';
 import { IUploadTarball, IReadTarball } from '@verdaccio/streams';
+import { generateVersion } from "../../../unit/__helper/utils";
 
-export default class ExampleMiddlewarePlugin implements IPluginMiddleware {
-  register_middlewares(app: any, auth: IBasicAuth, storage: IStorageManager): void {
+export default class ExampleMiddlewarePlugin implements IPluginMiddleware<{}> {
+  register_middlewares(app: any, auth: IBasicAuth<{}>, storage: IStorageManager<{}>): void {
     const remoteUser: RemoteUser = {
       groups: [],
       real_groups: [],
@@ -29,13 +32,12 @@ export default class ExampleMiddlewarePlugin implements IPluginMiddleware {
     auth.aesEncrypt(new Buffer('pass'));
     // storage
     storage.addPackage('name', generatePackageTemplate('test'), () => {});
-    storage.addVersion('name', 'version', readMetadata(), 'tag', () => {});
+    storage.addVersion('name', 'version', generateVersion('name', '1.0.0'), 'tag', () => {});
     storage.mergeTags('name', {'latest': '1.0.0'}, () => {});
-    storage.changePackage('name', readMetadata(), 'revision', () => {});
+    storage.changePackage('name', readMetadata('metadata'), 'revision', () => {});
     storage.removePackage('name', () => {});
     storage.mergeTags('name', {'latest': '1.0.0'}, () => {});
     storage.removeTarball('name', 'filename', 'revision', () => {});
-    /* eslint no-unused-vars: 0 */
     const config1: AppConfig = new Config({
       storage: './storage',
       self_path: '/home/sotrage'
@@ -43,8 +45,7 @@ export default class ExampleMiddlewarePlugin implements IPluginMiddleware {
     const add: IUploadTarball = storage.addTarball('name', 'filename');
     storage.getTarball('name', 'filename');
     const read: IReadTarball = storage.getTarball('name', 'filename');
-    const search: IReadTarball = storage.search('test');
-    /* eslint no-unused-vars: 0 */
+    const search: IReadTarball = storage.search('test', {});
   }
 }
 
diff --git a/test/flow/plugins/partials/config.example.js b/test/types-test/plugins/partials/config.example.js
similarity index 100%
rename from test/flow/plugins/partials/config.example.js
rename to test/types-test/plugins/partials/config.example.js
diff --git a/test/flow/plugins/storage/example.storage.plugin.js b/test/types-test/plugins/storage/example.storage.plugin.js
similarity index 100%
rename from test/flow/plugins/storage/example.storage.plugin.js
rename to test/types-test/plugins/storage/example.storage.plugin.js
diff --git a/test/types-test/plugins/storage/example.storage.plugin.ts b/test/types-test/plugins/storage/example.storage.plugin.ts
new file mode 100644
index 000000000..09c34e559
--- /dev/null
+++ b/test/types-test/plugins/storage/example.storage.plugin.ts
@@ -0,0 +1,171 @@
+// this file is not aim to be tested, just to check typescript definitions
+
+import {
+  Callback,
+  Config as AppConfig,
+  Logger,
+  Package,
+  Token,
+  TokenFilter,
+  IUploadTarball, IReadTarball
+} from '@verdaccio/types';
+
+import {
+  IPluginStorage,
+  IPackageStorageManager,
+  IPackageStorage
+} from '@verdaccio/types';
+import { UploadTarball, ReadTarball} from '@verdaccio/streams';
+
+import Config from '../../../../src/lib/config';
+import {logger} from '../../../../src/lib/logger';
+import {generatePackageTemplate} from '../../../../src/lib/storage-utils';
+
+class PackageStorage implements IPackageStorageManager {
+  path: string;
+  logger: Logger;
+
+  constructor(path: string, logger: Logger) {
+    this.path = path;
+    this.logger = logger;
+  }
+
+  updatePackage(name: string, updateHandler: Callback,
+    onWrite: Callback,
+    transformPackage: Function,
+    onEnd: Callback) {
+    onEnd();
+  }
+
+  deletePackage(fileName: string, callback: Callback) {
+    callback();
+  }
+
+  removePackage(callback: Callback): void {
+    callback();
+  }
+
+  createPackage(name: string, value: Package, cb: Callback) {
+    cb();
+  }
+
+  savePackage(name: string, value: Package, cb: Callback) {
+    cb();
+  }
+
+  readPackage(name: string, cb: Callback) {
+    cb();
+  }
+
+  writeTarball(name): IUploadTarball {
+    this.logger.debug({name}, 'some name @name');
+    const uploadStream = new UploadTarball({});
+    uploadStream.on('close', () => {});
+    if (uploadStream.abort) {
+      uploadStream.abort();
+    }
+
+    if (uploadStream.done) {
+      uploadStream.done();
+    }
+
+    return uploadStream;
+  }
+
+  readTarball(name): IReadTarball {
+    this.logger.debug({name}, 'some name @name');
+    const readTarballStream: IReadTarball = new ReadTarball({});
+
+    if (readTarballStream.abort) {
+      readTarballStream.abort();
+    }
+
+    return readTarballStream;
+  }
+}
+
+class ExampleStoragePlugin implements IPluginStorage<{}> {
+  logger: Logger;
+  config: AppConfig;
+
+  constructor(config: AppConfig, logger: Logger) {
+    this.config = config;
+    this.logger = logger;
+  }
+
+  saveToken(token: Token): Promise<any> {
+    return Promise.resolve(token)
+  }
+  deleteToken(user: string, tokenKey: string): Promise<any>{
+    return Promise.resolve([user, tokenKey]);
+  }
+
+  readTokens(filter: TokenFilter): Promise<Token[]> {
+    const token: Token = {
+      user: filter.user,
+      key: '12312',
+      token: '12321',
+      readonly: false,
+      created: '123232'
+    }
+
+    return Promise.resolve([token, token]);
+  }
+
+  getSecret(): Promise<any> {
+    return Promise.resolve();
+  }
+
+  setSecret(secret: string): Promise<any> {
+    return Promise.resolve(secret);
+  }
+
+  add(name: string, cb: Callback) {
+    cb();
+  }
+
+  remove(name: string, cb: Callback) {
+    cb();
+  }
+
+  get(cb: Callback) {
+    cb();
+  }
+
+  getPackageStorage(packageInfo: string): IPackageStorage {
+    return new PackageStorage(packageInfo, this.logger);
+  }
+
+  search(onPackage: Callback, onEnd: Callback, validateName: any): void {
+    onPackage(onEnd(validateName()));
+  }
+}
+
+export default ExampleStoragePlugin;
+
+const config1: AppConfig = new Config({
+  storage: './storage',
+  self_path: '/home/sotrage'
+});
+
+
+const storage = new ExampleStoragePlugin(config1, logger.child());
+
+storage.add('test', () => {});
+storage.remove('test', () => {});
+storage.getSecret().then(() => {});
+storage.setSecret('newSecret').then(() => {});
+storage.search(() => {}, () => {}, 'validateName');
+storage.get(() => {});
+
+const storageManager: IPackageStorage = storage.getPackageStorage('test');
+
+if (storageManager) {
+  storageManager.createPackage('test', generatePackageTemplate('test'), () => {});
+  storageManager.savePackage('fileName', generatePackageTemplate('test'), () => {});
+  storageManager.updatePackage('pkgFileName', () =>{}, () => {}, () => {}, () => {});
+  storageManager.deletePackage('test', () => {});
+  storageManager.removePackage(() => {});
+  storageManager.readPackage('test', () => {});
+  storageManager.writeTarball('test');
+}
diff --git a/test/types/index.ts b/test/types/index.ts
index 030ec2b71..b17677c4b 100644
--- a/test/types/index.ts
+++ b/test/types/index.ts
@@ -15,11 +15,6 @@ export interface IRequestPromise {
 }
 
 export interface IServerProcess {
-  bridge: IServerBridge;
-  config: IVerdaccioConfig;
-  childFork: any;
-  isDebug: boolean;
-  silence: boolean;
   init(): Promise<any>;
   stop(): void;
 }
diff --git a/test/unit/__helper/api.ts b/test/unit/__helper/api.ts
index 337c27d69..bf5710bc1 100644
--- a/test/unit/__helper/api.ts
+++ b/test/unit/__helper/api.ts
@@ -19,8 +19,7 @@ export function putPackage(
   request: any,
   pkgName: string,
   publishMetadata: Package,
-  token?: string,
-  httpStatus: number = HTTP_STATUS.CREATED): Promise<any[]> {
+  token?: string): Promise<any[]> {
   return new Promise((resolve) => {
     let put = request.put(pkgName)
         .set(HEADER_TYPE.CONTENT_TYPE, HEADERS.JSON)
diff --git a/test/unit/__helper/utils.ts b/test/unit/__helper/utils.ts
index bd3b0e9d4..9968671c4 100644
--- a/test/unit/__helper/utils.ts
+++ b/test/unit/__helper/utils.ts
@@ -1,6 +1,6 @@
 import { Package } from "@verdaccio/types";
 
-export function generateAttachment(pkgName, version) {
+export function generateAttachment() {
 	return {
 			"content_type": "application\/octet-stream",
 			"data": "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",
@@ -54,7 +54,7 @@ export function generatePackageBody(pkgName: string, _versions: string[] = ['1.0
 	}, {});
 
 	const attachtment = _versions.reduce((cat, version) => {
-		cat[`${pkgName}-${version}.tgz`] = generateAttachment(pkgName, version);
+		cat[`${pkgName}-${version}.tgz`] = generateAttachment();
 		return cat;
 	}, {});
 
@@ -106,8 +106,8 @@ export function generateStarMedatada(pkgName: string, users): any {
 	}
 }
 
-export function generatePackageMetadata(pkgName: string, version: string = '1.0.0'): Package {
-	// @ts-ignore 
+export function generatePackageMetadata(pkgName: string, version = '1.0.0'): Package {
+	// @ts-ignore
 	return {
 		"_id": pkgName,
 		"name": pkgName,
diff --git a/test/unit/modules/access/pkg.access.spec.ts b/test/unit/modules/access/pkg.access.spec.ts
index a7207b3c9..b60fe98ee 100644
--- a/test/unit/modules/access/pkg.access.spec.ts
+++ b/test/unit/modules/access/pkg.access.spec.ts
@@ -101,7 +101,7 @@ describe('api with no limited access configuration', () => {
         .set(HEADERS.CONTENT_TYPE, HEADERS.JSON_CHARSET)
         .expect(HEADERS.CONTENT_TYPE, /json/)
         .expect(HTTP_STATUS.OK)
-        .end(function(err, res) {
+        .end(function(err) {
           if (err) {
             return done(err);
           }
diff --git a/test/unit/modules/api/api.spec.ts b/test/unit/modules/api/api.spec.ts
index fa631a555..8d2639f2a 100644
--- a/test/unit/modules/api/api.spec.ts
+++ b/test/unit/modules/api/api.spec.ts
@@ -405,7 +405,7 @@ describe('endpoint unit test', () => {
           .set(HEADER_TYPE.CONTENT_TYPE, HEADERS.JSON_CHARSET)
           .expect(HEADER_TYPE.CONTENT_TYPE, HEADERS.JSON_CHARSET)
           .expect(HTTP_STATUS.NOT_FOUND)
-          .end(function(err, res) {
+          .end(function(err) {
             if (err) {
               return done(err);
             }
@@ -437,7 +437,7 @@ describe('endpoint unit test', () => {
             .set(HEADER_TYPE.CONTENT_TYPE, HEADERS.JSON_CHARSET)
             .expect(HEADER_TYPE.CONTENT_TYPE, HEADERS.JSON_CHARSET)
             .expect(HTTP_STATUS.NOT_FOUND)
-            .end(function(err, res) {
+            .end(function(err) {
               if (err) {
                 return done(err);
               }
@@ -716,7 +716,7 @@ describe('endpoint unit test', () => {
           }
 
           const deletePayload =  generatePackageUnpublish(pkgName, ['2.0.0']);
-          const [err2, res2] = await putPackage(request(app), generateUnPublishURI(pkgName), deletePayload, token, HTTP_STATUS.FORBIDDEN);
+          const [err2, res2] = await putPackage(request(app), generateUnPublishURI(pkgName), deletePayload, token);
 
           expect(err2).not.toBeNull();
           expect(res2.body.error).toMatch(/user jota_unpublish_fail is not allowed to unpublish package non-unpublish/);
diff --git a/test/unit/modules/api/partials/plugin/filter.js b/test/unit/modules/api/partials/plugin/filter.ts
similarity index 88%
rename from test/unit/modules/api/partials/plugin/filter.js
rename to test/unit/modules/api/partials/plugin/filter.ts
index 994554f55..a3caa169c 100644
--- a/test/unit/modules/api/partials/plugin/filter.js
+++ b/test/unit/modules/api/partials/plugin/filter.ts
@@ -1,9 +1,10 @@
 class FilterPlugin {
-  constructor(config) {
+  private _config;
+  public constructor(config) {
     this._config = config;
   }
 
-  filter_metadata(pkg) {
+  public filter_metadata(pkg) {
     return new Promise((resolve, reject) => {
       // We use this to test what happens when a filter rejects
       if(pkg.name === 'trigger-filter-failure') {
diff --git a/test/unit/modules/api/publish.spec.ts b/test/unit/modules/api/publish.spec.ts
index 00725e749..2bad6835e 100644
--- a/test/unit/modules/api/publish.spec.ts
+++ b/test/unit/modules/api/publish.spec.ts
@@ -270,7 +270,7 @@ describe('Publish endpoints - publish package', () => {
     test('should star a package', () => {
       const storage = {
         changePackage: jest.fn(),
-        getPackage({ name, req, callback }) {
+        getPackage({ callback }) {
           callback(null, {
             users: {},
           });
diff --git a/test/unit/modules/api/token.spec.ts b/test/unit/modules/api/token.spec.ts
index dcb361cd1..9800cec0b 100644
--- a/test/unit/modules/api/token.spec.ts
+++ b/test/unit/modules/api/token.spec.ts
@@ -162,7 +162,7 @@ describe('endpoint unit test', () => {
         .set(HEADERS.AUTHORIZATION, buildToken(TOKEN_BEARER, token))
         .expect(HEADER_TYPE.CONTENT_TYPE, HEADERS.JSON_CHARSET)
         .expect(HTTP_STATUS.OK)
-        .end(function(err, resp) {
+        .end(function(err) {
           if (err) {
             return done(err);
           }
diff --git a/test/unit/modules/cli/cli.spec.ts b/test/unit/modules/cli/cli.spec.ts
index f3929d1ee..d46e9b558 100644
--- a/test/unit/modules/cli/cli.spec.ts
+++ b/test/unit/modules/cli/cli.spec.ts
@@ -6,8 +6,7 @@ import config from '../../partials/config';
 import {DEFAULT_DOMAIN, DEFAULT_PORT, DEFAULT_PROTOCOL} from '../../../../src/lib/constants';
 import {getListListenAddresses} from '../../../../src/lib/cli/utils';
 import {parseConfigFile} from '../../../../src/lib/utils';
-
-const logger = require('../../../../src/lib/logger');
+import { logger } from '../../../../src/lib/logger';
 
 jest.mock('../../../../src/lib/logger', () => ({
   setup: jest.fn(),
@@ -132,8 +131,8 @@ describe('startServer via API', () => {
       // @ts-ignore
       global.process = { ...realProcess, exit: exitMock };
       await startServer(conf, address, store, version, serverName, () => {
-        expect(logger.logger.fatal).toHaveBeenCalled();
-        expect(logger.logger.fatal).toHaveBeenCalledTimes(2);
+        expect(logger.fatal).toHaveBeenCalled();
+        expect(logger.fatal).toHaveBeenCalledTimes(2);
         done();
       });
       expect(exitMock).toHaveBeenCalledWith(2);
diff --git a/test/unit/modules/notifications/request.spec.ts b/test/unit/modules/notifications/request.spec.ts
index 8b3ce8579..f4d05e991 100644
--- a/test/unit/modules/notifications/request.spec.ts
+++ b/test/unit/modules/notifications/request.spec.ts
@@ -1,4 +1,5 @@
 import { HTTP_STATUS, API_ERROR } from '../../../../src/lib/constants';
+/* eslint-disable @typescript-eslint/no-var-requires */
 
 /**
  * Mocks Logger Service
diff --git a/test/unit/modules/plugin/partials/test-plugin-storage/.eslintrc b/test/unit/modules/plugin/partials/test-plugin-storage/.eslintrc
new file mode 100644
index 000000000..a521e4fe8
--- /dev/null
+++ b/test/unit/modules/plugin/partials/test-plugin-storage/.eslintrc
@@ -0,0 +1,5 @@
+{
+  "rules": {
+    "@typescript-eslint/no-empty-function": 0
+  }
+}
diff --git a/test/unit/modules/plugin/partials/test-plugin-storage/invalid-plugin-sanity/index.js b/test/unit/modules/plugin/partials/test-plugin-storage/invalid-plugin-sanity/index.js
index 18feb62a9..bf345d0f2 100644
--- a/test/unit/modules/plugin/partials/test-plugin-storage/invalid-plugin-sanity/index.js
+++ b/test/unit/modules/plugin/partials/test-plugin-storage/invalid-plugin-sanity/index.js
@@ -1,6 +1,7 @@
 function ValidVerdaccioPlugin() {
   return {
     // not valid method
+    // eslint-disable-next-line  @typescript-eslint/no-empty-function
     authenticate__: function(){}
   }
 }
diff --git a/test/unit/modules/plugin/partials/test-plugin-storage/verdaccio-es6-plugin/dummy.js b/test/unit/modules/plugin/partials/test-plugin-storage/verdaccio-es6-plugin/dummy.js
index 3c641b39e..e002568cc 100644
--- a/test/unit/modules/plugin/partials/test-plugin-storage/verdaccio-es6-plugin/dummy.js
+++ b/test/unit/modules/plugin/partials/test-plugin-storage/verdaccio-es6-plugin/dummy.js
@@ -1,3 +1,5 @@
+// this is how a Babel.js transpiled plugin looks like
+
 "use strict";
 
 Object.defineProperty(exports, "__esModule", {
@@ -19,10 +21,10 @@ var Dummy = function () {
 
   _createClass(Dummy, [{
     key: "getPackageStorage",
-    value: function getPackageStorage(packageInfo, packagePath) {}
+    value: function getPackageStorage() {}
   }]);
 
   return Dummy;
 }();
 
-exports.default = Dummy;
\ No newline at end of file
+exports.default = Dummy;
diff --git a/test/unit/modules/plugin/partials/test-plugin-storage/verdaccio-es6-plugin/index.js b/test/unit/modules/plugin/partials/test-plugin-storage/verdaccio-es6-plugin/index.js
index 9294c94d4..a01985c72 100644
--- a/test/unit/modules/plugin/partials/test-plugin-storage/verdaccio-es6-plugin/index.js
+++ b/test/unit/modules/plugin/partials/test-plugin-storage/verdaccio-es6-plugin/index.js
@@ -1,4 +1,5 @@
 'use strict';
+/* eslint-disable @typescript-eslint/no-var-requires */
 
 Object.defineProperty(exports, "__esModule", {
   value: true
diff --git a/test/unit/modules/storage/local-storage.spec.ts b/test/unit/modules/storage/local-storage.spec.ts
index 2fd9690c2..f25e79414 100644
--- a/test/unit/modules/storage/local-storage.spec.ts
+++ b/test/unit/modules/storage/local-storage.spec.ts
@@ -10,7 +10,7 @@ import {readFile} from '../../../functional/lib/test.utils';
 import {generatePackageTemplate} from '../../../../src/lib/storage-utils';
 import {generateNewVersion} from '../../../lib/utils-test';
 
-const readMetadata = (fileName: string = 'metadata') => readFile(`../../unit/partials/${fileName}`).toString();
+const readMetadata = (fileName = 'metadata') => readFile(`../../unit/partials/${fileName}`).toString();
 
 import {Config, MergeTags, Package} from '@verdaccio/types';
 import {IStorage} from '../../../../types';
@@ -216,7 +216,7 @@ describe('LocalStorage', () => {
         await addPackageToStore(pkgName, generatePackageTemplate(pkgName));
         await addNewVersion(pkgName, version);
 
-        storage.addVersion(pkgName, version, generateNewVersion(pkgName, version), '', (err, data) => {
+        storage.addVersion(pkgName, version, generateNewVersion(pkgName, version), '', err => {
           expect(err).not.toBeNull();
           expect(err.statusCode).toEqual(HTTP_STATUS.CONFLICT);
           expect(err.message).toMatch(API_ERROR.PACKAGE_EXIST);
@@ -231,7 +231,7 @@ describe('LocalStorage', () => {
         const tarballName = `${pkgName}-${version}.tgz`;
         await addTarballToStore(pkgName, tarballName);
 
-        storage.addVersion(pkgName, version, generateNewVersion(pkgName, version, 'fake'), '', (err, data) => {
+        storage.addVersion(pkgName, version, generateNewVersion(pkgName, version, 'fake'), '', err => {
           expect(err).not.toBeNull();
           expect(err.statusCode).toEqual(HTTP_STATUS.BAD_REQUEST);
           expect(err.message).toMatch(/shasum error/);
@@ -503,7 +503,7 @@ describe('LocalStorage', () => {
 
       test('should fails with package not found', (done) => {
         const pkgName = 'npm_test_fake';
-        storage.removePackage(pkgName, (err, data) => {
+        storage.removePackage(pkgName, err => {
           expect(err).not.toBeNull();
           expect(err.message).toMatch(/no such package available/);
           done();
@@ -511,7 +511,7 @@ describe('LocalStorage', () => {
       });
 
       test('should fails with @scoped package not found', (done) => {
-        storage.removePackage(pkgNameScoped, (err, data) => {
+        storage.removePackage(pkgNameScoped, err => {
           expect(err).not.toBeNull();
           expect(err.message).toMatch(API_ERROR.NO_PACKAGE);
           done();
diff --git a/test/unit/modules/storage/storage-utils.spec.ts b/test/unit/modules/storage/storage-utils.spec.ts
index be60aedb2..9ae672b0a 100644
--- a/test/unit/modules/storage/storage-utils.spec.ts
+++ b/test/unit/modules/storage/storage-utils.spec.ts
@@ -4,7 +4,7 @@ import {readFile} from "../../../functional/lib/test.utils";
 
 import {Package} from '@verdaccio/types';
 
-const readMetadata = (fileName: string = 'metadata') => readFile(`../../unit/partials/${fileName}`);
+const readMetadata = (fileName = 'metadata') => readFile(`../../unit/partials/${fileName}`);
 
 describe('Storage Utils', () => {
   describe('normalizePackage', () => {
diff --git a/test/unit/modules/storage/store.spec.ts b/test/unit/modules/storage/store.spec.ts
index 3743f3cde..6c6447ca9 100644
--- a/test/unit/modules/storage/store.spec.ts
+++ b/test/unit/modules/storage/store.spec.ts
@@ -60,7 +60,7 @@ describe('StorageTest', () => {
       const storage: IStorageHandler = await generateStorage();
 
       // @ts-ignore
-      storage._syncUplinksMetadata('jquery', null, {}, (err, metadata, errors) => {
+      storage._syncUplinksMetadata('jquery', null, {}, (err, metadata) => {
         expect(err).toBeNull();
         expect(metadata).toBeDefined();
         expect(metadata).toBeInstanceOf(Object);
diff --git a/test/unit/modules/uplinks/up-storage.spec.ts b/test/unit/modules/uplinks/up-storage.spec.ts
index 1497968f8..5af4b122c 100644
--- a/test/unit/modules/uplinks/up-storage.spec.ts
+++ b/test/unit/modules/uplinks/up-storage.spec.ts
@@ -156,7 +156,7 @@ describe('UpStorge', () => {
     describe('valid use cases', () => {
       const validateUpLink = (
         url: string,
-        tarBallUrl: string = `${url}/artifactory/api/npm/npm/pk1-juan/-/pk1-juan-1.0.7.tgz`) => {
+        tarBallUrl = `${url}/artifactory/api/npm/npm/pk1-juan/-/pk1-juan-1.0.7.tgz`) => {
         const uplinkConf = { url };
         const proxy: IProxy = generateProxy(uplinkConf);
 
diff --git a/test/unit/modules/utils/utils.spec.ts b/test/unit/modules/utils/utils.spec.ts
index b2c3e941f..e1b3fccd8 100644
--- a/test/unit/modules/utils/utils.spec.ts
+++ b/test/unit/modules/utils/utils.spec.ts
@@ -20,7 +20,7 @@ import { DIST_TAGS, DEFAULT_USER } from '../../../../src/lib/constants';
 import { logger, setup } from '../../../../src/lib/logger';
 import { readFile } from '../../../functional/lib/test.utils';
 
-const readmeFile = (fileName: string = 'markdown.md') =>
+const readmeFile = (fileName = 'markdown.md') =>
   readFile(`../../unit/partials/readme/${fileName}`);
 
 setup([]);
diff --git a/test/unit/partials/config/index.js b/test/unit/partials/config/index.js
index 8863a9f1b..5edf37675 100644
--- a/test/unit/partials/config/index.js
+++ b/test/unit/partials/config/index.js
@@ -1,12 +1,15 @@
 
 import _ from 'lodash';
 import path from 'path';
+
 import {parseConfigFile} from '../../../../src/lib/utils';
 
-
+/**
+ * Override the default.yaml configuration file with any new config provided.
+ */
 export default (options, url = 'default.yaml') => {
   const locationFile = path.join(__dirname, `../config/yaml/${url}`);
   const config = parseConfigFile(locationFile);
-  
+
   return _.assign({}, _.cloneDeep(config), options);
 }
diff --git a/test/unit/partials/config/json/README.md b/test/unit/partials/config/json/README.md
new file mode 100644
index 000000000..a8e393aa1
--- /dev/null
+++ b/test/unit/partials/config/json/README.md
@@ -0,0 +1,7 @@
+# JSON Configurations
+
+This folder host all sort of JSON configurations for testing. **It should not include many scenarios, since we use `yaml` for testing. JSON files on this folder aims to verify a verdaccio JSON config file works properly.
+
+## Contribute
+
+- Don't add new scenarios unless is discussed with the core team.
diff --git a/test/unit/partials/config/yaml/README.md b/test/unit/partials/config/yaml/README.md
new file mode 100644
index 000000000..d643e410e
--- /dev/null
+++ b/test/unit/partials/config/yaml/README.md
@@ -0,0 +1,16 @@
+# Yaml Configurations
+
+This folder host all sort of configurations for testing. We use `yaml` instead json configuration files for different reasons, maintenability, avoid polute with non use data and contributors can easily understand them.
+
+The files on this folder should be small as possible, **there is a custom config file for all tests (`default.yaml`)** and the following configuration aims to override those part are need it for the test.
+
+## Contribute
+
+- Each topic ideally should have his **own folder** if many scenarios might be part of the test. **eg: profile, security**
+  - Include different scenarios inside of the folder with enough context to indenty the use case.
+- Foder or file, should be **named** as the test that used them. *eg: `api.spec.yaml` -> `api.spec.ts`*
+- **Don't use the same config file in multiple test**, it increase maintenance complexity.
+- Try to **include only the props are require for the test**:
+- Comment the config files, don't be shy, add as much context you think is need it for future contributors.
+
+> Note: Some configurations might be not aligned with this rules, but in the future all files should be follow them for consistency.
diff --git a/test/unit/partials/config/yaml/token.spec.yaml b/test/unit/partials/config/yaml/token.spec.yaml
index df8bdde76..87ddb880a 100644
--- a/test/unit/partials/config/yaml/token.spec.yaml
+++ b/test/unit/partials/config/yaml/token.spec.yaml
@@ -7,6 +7,7 @@ security:
     jwt:
       sign:
         expiresIn: 5m
+        # to avoid invalid verification token, more info on JWT page
         notBefore: 0
 packages:
   '@token/*':
@@ -18,5 +19,5 @@ packages:
 logs:
   - { type: stdout, format: pretty, level: trace }
 experiments:
-  ## Enable token for testing
+  ## enable token for testing
   token: true
diff --git a/tsconfig.json b/tsconfig.json
index da919fb00..2a10c0a5b 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -6,6 +6,7 @@
     "noImplicitAny": false,
     "strict": true,
     "strictNullChecks": true,
+    "resolveJsonModule": true,
     "outDir": "lib",
     "allowSyntheticDefaultImports": true,
     "esModuleInterop": true,
diff --git a/types/index.ts b/types/index.ts
index 24d80746e..01ed49fca 100644
--- a/types/index.ts
+++ b/types/index.ts
@@ -187,7 +187,7 @@ export interface IStorageHandler extends IStorageManager<Config>, ITokenActions
   init(config: Config, filters: IPluginFilters): Promise<string>;
   saveToken(token: Token): Promise<any>;
   deleteToken(user: string, tokenKey: string): Promise<any>;
-  readTokens(filter: TokenFilter): Promise<Array<Token>>;
+  readTokens(filter: TokenFilter): Promise<Token[]>;
   _syncUplinksMetadata(name: string, packageInfo: Package, options: any, callback: Callback): void;
   _updateVersionsHiddenUpLink(versions: Versions, upLink: IProxy): void;
 }