test.js

// Get the contract instance using your contract's abi and address: 
const contractInstance = web3.eth.contract(abi).at(contractAddress);

// Get user’s web3 address
var sender = web3.eth.accounts[0];

// Call a function of the contract: 
contractInstance.someFunction({ 
 from: sender, value: someValue, gas: limit 
}, (err, res) => { /** do something with results **/ });