Truffle Mocha MetaCoin Test refactoring

Truffle Mocha MetaCoin each

var MetaCoin = artifacts.require("./MetaCoin.sol");

contract('MetaCoin', (accounts) => {
  describe('Token', () =>  {
    let balance;
    let instance;
    const [alice, bob] = accounts;

    before(async () => {
      instance = await MetaCoin.deployed();
    });

    it("should put 10000 MetaCoin in the first account", async () => {
      let balance = await instance.getBalance.call(alice);
      assert.equal(balance.valueOf(), 10000, "10000 wasn't in the first account");
    });

    it("should send coin correctly", async () => {
      // Get initial balances of first and second account.
      var amount = 10;
      balance = await instance.getBalance.call(alice);
      let alice_balance = balance.toNumber();
      balance = await instance.getBalance.call(bob);
      let bob_balance = balance.toNumber();

      await instance.sendCoin(bob, amount, { from: alice });

      balance = await instance.getBalance.call(alice);
      let alice_ending_balance = balance.toNumber();
      balance = await instance.getBalance.call(bob);
      let bob_ending_balance   = balance.toNumber();

      assert.equal(alice_ending_balance, alice_balance - amount, "Amount wasn't correctly taken from the sender");
      assert.equal(bob_ending_balance, bob_balance + amount, "Amount wasn't correctly sent to the receiver");
    });
  });

  describe('Library', () => {
    it("should call a function that depends on a linked library", async () => {
      let alice = accounts[0];
      let meta = await MetaCoin.deployed();
      let outCoinBalance = await meta.getBalance.call(alice);
      let metaCoinBalance = outCoinBalance.toNumber();
      let outCoinBalanceEth = await meta.getBalanceInEth.call(alice);
      let metaCoinEthBalance = outCoinBalanceEth.toNumber();

      assert.equal(metaCoinEthBalance, 2 * metaCoinBalance, "Library function returned unexpected function, linkage may be broken");
    });
  });
});