Organization.test.js

const Organization = artifacts.require("Organization");

contract('Organization', (accounts) => {
    let contractInstance;
    const creator = accounts[0];    

    beforeEach(async function () {        
        contractInstance = await Organization.new(4, 4, { from: creator });
    });

    describe("# addMember()", () => {
        it("should add a new member", async () => {
            //arrange
            let memberToAdd = accounts[1];
            let transactionCall;
            let memberExist;

            //act
            transactionCall = await contractInstance.addMember.call(memberToAdd);
            await contractInstance.addMember(memberToAdd);            
            memberExist = await contractInstance.members(memberToAdd);
            
            //assert
            assert.equal(transactionCall, true);
            assert.equal(memberExist, true);            
        })       
    })
});

//For more information about Mocha test suites
//https://gist.github.com/samwize/8877226#file-mocha-guide-to-testing-js-L53