diff --git a/src/framework/ajv/index.ts b/src/framework/ajv/index.ts
index b5d753dc..f05f0445 100644
--- a/src/framework/ajv/index.ts
+++ b/src/framework/ajv/index.ts
@@ -21,7 +21,7 @@ export function createResponseAjv(
 function createAjv(
   openApiSpec: OpenAPIV3.Document,
   options: ajv.Options = {},
-  request = true,
+  request: boolean = true,
 ): Ajv.Ajv {
   const ajv = new Ajv({
     ...options,
diff --git a/src/framework/openapi.schema.validator.ts b/src/framework/openapi.schema.validator.ts
index 9e9d638f..8d85d6ca 100644
--- a/src/framework/openapi.schema.validator.ts
+++ b/src/framework/openapi.schema.validator.ts
@@ -3,10 +3,17 @@ import * as merge from 'lodash.merge';
 import * as draftSchema from 'ajv/lib/refs/json-schema-draft-04.json';
 // https://github.com/OAI/OpenAPI-Specification/blob/master/schemas/v3.0/schema.json
 import * as openapi3Schema from './openapi.v3.schema.json';
+import { OpenAPIV3 } from './types.js';
 
 export class OpenAPISchemaValidator {
   private validator: Ajv.ValidateFunction;
-  constructor({ version, extensions }: { version: string; extensions?: object }) {
+  constructor({
+    version,
+    extensions,
+  }: {
+    version: string;
+    extensions?: object;
+  }) {
     const v = new Ajv({ schemaId: 'auto', allErrors: true });
     v.addMetaSchema(draftSchema);
 
@@ -19,7 +26,9 @@ export class OpenAPISchemaValidator {
     this.validator = v.compile(schema);
   }
 
-  public validate(openapiDoc) {
+  public validate(
+    openapiDoc: OpenAPIV3.Document,
+  ): { errors: Array<Ajv.ErrorObject> | null } {
     const valid = this.validator(openapiDoc);
     if (!valid) {
       return { errors: this.validator.errors };
diff --git a/src/framework/types.ts b/src/framework/types.ts
index 74e1cec9..db8fd0ca 100644
--- a/src/framework/types.ts
+++ b/src/framework/types.ts
@@ -1,4 +1,4 @@
-import ajv = require('ajv');
+import * as ajv from 'ajv';
 import { Request, Response, NextFunction } from 'express';
 export { OpenAPIFrameworkArgs };
 
diff --git a/src/middlewares/openapi.response.validator.ts b/src/middlewares/openapi.response.validator.ts
index 459d4d42..937bf5f7 100644
--- a/src/middlewares/openapi.response.validator.ts
+++ b/src/middlewares/openapi.response.validator.ts
@@ -58,7 +58,7 @@ export class ResponseValidator {
   }
 
   // TODO public for test only - fix me
-  _validate({ validators, body, statusCode, path }) {
+  public _validate({ validators, body, statusCode, path }) {
     // find the validator for the 'status code' e.g 200, 2XX or 'default'
     let validator;
     const status = statusCode;
diff --git a/src/middlewares/openapi.security.ts b/src/middlewares/openapi.security.ts
index 9648ab7f..919a77ac 100644
--- a/src/middlewares/openapi.security.ts
+++ b/src/middlewares/openapi.security.ts
@@ -3,6 +3,7 @@ import {
   OpenApiRequest,
   SecurityHandlers,
   OpenApiRequestMetadata,
+  OpenApiRequestHandler,
 } from '../framework/types';
 import { validationError } from './util';
 import { OpenApiContext } from '../framework/openapi.context';
@@ -21,7 +22,7 @@ interface SecurityHandlerResult {
 export function security(
   context: OpenApiContext,
   securityHandlers: SecurityHandlers,
-) {
+): OpenApiRequestHandler {
   return async (req, res, next) => {
     // TODO move the folllowing 3 check conditions to a dedicated upstream middleware
     if (!req.openapi) {
@@ -31,12 +32,13 @@ export function security(
       return next();
     }
 
-    const expressRoute = req.openapi.expressRoute;
+    const openapi = <OpenApiRequestMetadata>req.openapi;
+    const expressRoute = openapi.expressRoute;
     if (!expressRoute) {
       return next(validationError(404, req.path, 'not found'));
     }
 
-    const pathSchema = req.openapi.schema;
+    const pathSchema = openapi.schema;
     if (!pathSchema) {
       // add openapi metadata to make this case more clear
       // its not obvious that missig schema means methodNotAllowed
@@ -47,9 +49,9 @@ export function security(
 
     // use the local security object or fallbac to api doc's security or undefined
     const securities: OpenAPIV3.SecurityRequirementObject[] =
-      req.openapi.schema.security ?? context.apiDoc.security;
+      openapi.schema.security ?? context.apiDoc.security;
 
-    const path: string = req.openapi.openApiRoute;
+    const path: string = openapi.openApiRoute;
 
     if (!path || !Array.isArray(securities) || securities.length === 0) {
       return next();
@@ -94,8 +96,8 @@ export function security(
 class SecuritySchemes {
   private securitySchemes;
   private securityHandlers: SecurityHandlers;
-  private securities;
-  constructor(securitySchemes, securityHandlers: SecurityHandlers, securities) {
+  private securities: OpenAPIV3.SecurityRequirementObject[];
+  constructor(securitySchemes, securityHandlers: SecurityHandlers, securities: OpenAPIV3.SecurityRequirementObject[]) {
     this.securitySchemes = securitySchemes;
     this.securityHandlers = securityHandlers;
     this.securities = securities;
diff --git a/test/common/app.common.ts b/test/common/app.common.ts
index 5a3f5f9b..3ade110c 100644
--- a/test/common/app.common.ts
+++ b/test/common/app.common.ts
@@ -1,3 +1,4 @@
+import { NextFunction, Request, Response } from 'express';
 import * as http from 'http';
 import * as express from 'express';
 
@@ -17,22 +18,22 @@ export function routes(app) {
   const basePath = app.basePath;
   const router1 = express
     .Router()
-    .post('/', function(req, res, next) {
+    .post('/', function(req: Request, res: Response) {
       res.json({
         name: `${req.method}: /router_1`,
       });
     })
-    .get('/', function(req, res, next) {
+    .get('/', function(req: Request, res: Response) {
       res.json({
         name: `${req.method}: /router_1`,
       });
     })
-    .get('/:id', function(req, res, next) {
+    .get('/:id', function(req: Request, res: Response) {
       res.json({
         name: `${req.method}: /router_1/${req.params.id}`,
       });
     })
-    .get('/:id/best/:bid', function(req, res, next) {
+    .get('/:id/best/:bid', function(req: Request, res: Response) {
       res.json({
         name: `${req.method}: /router_1/${req.params.id}/best/${req.params.bid}`,
       });
@@ -40,36 +41,38 @@ export function routes(app) {
 
   app.use(`${basePath}/router_1`, router1);
 
-  app.get(`${basePath}/pets`, function(req, res, next) {
+  app.get(`${basePath}/pets`, function(req: Request, res: Response) {
     res.json({
       test: 'hi',
       ...req.body,
     });
   });
 
-  app.post(`${basePath}/pets`, function(req, res, next) {
+  app.post(`${basePath}/pets`, function(req: Request, res: Response) {
     res.json({
       ...req.body,
       id: 'new-id',
     });
   });
 
-  app.get(`${basePath}/pets/:id`, function(req, res, next) {
+  app.get(`${basePath}/pets/:id`, function(req: Request, res: Response) {
     res.json({
       id: req.params.id,
     });
   });
 
-  app.get(`${basePath}/pets/:id/attributes`, function(req, res, next) {
+  app.get(`${basePath}/pets/:id/attributes`, function(
+    req: Request,
+    res: Response,
+  ) {
     res.json({
       id: req.params.id,
     });
   });
 
   app.get(`${basePath}/pets/:id/attributes/:attribute_id`, function(
-    req,
-    res,
-    next,
+    req: Request,
+    res: Response,
   ) {
     res.json({
       id: req.params.id,
@@ -78,22 +81,24 @@ export function routes(app) {
   });
 
   app.post(`${basePath}/route_defined_in_express_not_openapi`, function(
-    req,
-    res,
-    next,
+    req: Request,
+    res: Response,
   ) {
     res.json({
       id: req.params.id,
     });
   });
 
-  app.get('/not_under_an_openapi_basepath', function(req, res, next) {
+  app.get('/not_under_an_openapi_basepath', function(
+    req: Request,
+    res: Response,
+  ) {
     res.json({
       id: '/not_under_an_openapi_basepath',
     });
   });
 
-  app.post('/v1/pets/:id/photos', function(req, res, next) {
+  app.post('/v1/pets/:id/photos', function(req: Request, res: Response) {
     // req.file is the `avatar` file
     // req.body will hold the text fields, if there were any
     const files = req.files;
@@ -102,7 +107,7 @@ export function routes(app) {
       metadata: req.body.metadata,
     });
   });
-  app.post('/v1/pets_charset', function (req: Request, res: any) {
+  app.post('/v1/pets_charset', function(req: Request, res: Response) {
     // req.file is the `avatar` file
     // req.body will hold the text fields, if there were any
     res.json({
diff --git a/test/common/app.ts b/test/common/app.ts
index cb1e84ee..c67bec43 100644
--- a/test/common/app.ts
+++ b/test/common/app.ts
@@ -10,9 +10,9 @@ import { OpenApiValidatorOpts } from '../../src/framework/types';
 
 export async function createApp(
   opts?: OpenApiValidatorOpts,
-  port = 3000,
+  port: number = 3000,
   customRoutes = app => {},
-  useRoutes = true,
+  useRoutes: boolean = true,
 ) {
   var app = express();
   (<any>app).basePath = '/v1';
diff --git a/test/openapi.spec.ts b/test/openapi.spec.ts
index 0944f96a..2b1b7c14 100644
--- a/test/openapi.spec.ts
+++ b/test/openapi.spec.ts
@@ -5,7 +5,7 @@ import { createApp } from './common/app';
 import * as packageJson from '../package.json';
 
 describe(packageJson.name, () => {
-  let apps = [];
+  const apps = [];
   let basePath = null;
 
   before(() => {
diff --git a/test/path.level.parameters.spec.ts b/test/path.level.parameters.spec.ts
index 3bfa00e9..b316cfd3 100644
--- a/test/path.level.parameters.spec.ts
+++ b/test/path.level.parameters.spec.ts
@@ -7,7 +7,6 @@ import * as packageJson from '../package.json';
 
 describe(packageJson.name, () => {
   let app = null;
-  let basePath = null;
 
   before(async () => {
     // Set up the express app
diff --git a/test/query.params.spec.ts b/test/query.params.spec.ts
index 1539b828..0d3e6247 100644
--- a/test/query.params.spec.ts
+++ b/test/query.params.spec.ts
@@ -7,7 +7,6 @@ import * as packageJson from '../package.json';
 
 describe(packageJson.name, () => {
   let app = null;
-  let basePath = null;
 
   before(async () => {
     // Set up the express app
diff --git a/test/security.handlers.spec.ts b/test/security.handlers.spec.ts
index a51e675b..96fa2e91 100644
--- a/test/security.handlers.spec.ts
+++ b/test/security.handlers.spec.ts
@@ -290,7 +290,7 @@ describe('security.handlers', () => {
     const validateSecurity = <ValidateSecurityOpts>eovConf.validateSecurity;
     validateSecurity.handlers.OAuth2 = function(
       req,
-      scopes,
+      scopes: string[],
       schema: OpenAPIV3.OAuth2SecurityScheme,
     ) {
       expect(schema.type).to.equal('oauth2');