Update README.md

README.md

@@ -3,6 +3,7 @@
 [![Build Status](https://neqsim.visualstudio.com/neqsim_cicd/_apis/build/status/neqsim_build?branchName=master)](https://neqsim.visualstudio.com/neqsim_cicd/_build/latest?definitionId=1&branchName=master)
 ![Build maven](https://github.com/equinor/neqsim/workflows/Build%20maven/badge.svg?branch=master)
 [![Known Vulnerabilities](https://snyk.io/test/github/equinor/neqsim/badge.svg)](https://snyk.io/test/github/equinor/neqsim)
+[![codecov](https://codecov.io/gh/equinor/neqsim/branch/add_code_coverage/graph/badge.svg?token=keVAcWavZ1)](https://codecov.io/gh/equinor/neqsim)
 
 NeqSim is the main part of the [NeqSim project](https://equinor.github.io/neqsimhome/). NeqSim (Non-Equilibrium Simulator) is a Java library for estimating fluid behavior and process design for oil and gas production.
 The basis for NeqSim is a library of fundamental mathematical models related to phase behavior and physical properties of oil and gas.  NeqSim is easilly extended with new models. NeqSim development was initiated at the [Norwegian University of Science and Technology (NTNU)](https://www.ntnu.edu/employees/even.solbraa).