struct Post {
        uint256 amt;
        bool isActive;
        address owner;
    }

    Post[] public posts;

    function createP(uint256 amt) public payable returns(uint a) {
        posts.push(Post({
            amt: amt,
            isActive: false,
            owner: msg.sender
        }));
        return (posts.length);
    }
    function getPostLength() returns(uint a){
        return (posts.length);
    }

MyContract.deployed()
        .then(async instance => {
            const weiSpend = web3.toWei(2, "ether");
            var id = await instance.createP.call(10,{
                from: accounts[0],
                value: weiSpend
            });
        var id2 = await instance.createP.call(50,{
          from: accounts[1],
          value: weiSpend
        });
        var id3 = await instance.createP.call(100,{
          from: accounts[2],
          value: weiSpend
        });
        var last = await instance.getPostLength.call();
        console.log(id3.toString()); // returns 1 instead of 3
        console.log(last.toString()); // returns 0 instead of 3
        });