智能合约测试-“未捕获的类型错误：无法读取未定义的属性‘调用’”

如何解决智能合约测试-“未捕获的类型错误：无法读取未定义的属性‘调用’”

我正在尝试测试我编写的 ERC20 合约。当我运行 truffle test 时，它不断返回以下错误：

    ✓ Should deploy smart contract properly
    1) "before each" hook: before test for "should call a function that depends on a linked library"
    2) "before each" hook: before test for "should call a function that depends on a linked library"


  1 passing (172ms)
  2 failing

  1) Contract: My
       "before each" hook: before test for "should call a function that depends on a linked library":
     Uncaught TypeError: Cannot read property 'call' of undefined
      at /Users/.../test/myToken.js:8:47
      at processticksAndRejections (node:internal/process/task_queues:96:5)

  2) Contract: My
       "before each" hook: before test for "should call a function that depends on a linked library":
     Error: done() called multiple times in hook <Contract: MyToken "before each" hook: before test for "should call a function that depends on a linked library"> of file ...


UnhandledRejections detected
Promise {
  <rejected> TypeError: Cannot read property 'call' of undefined
      at /Users/.../myToken.js:8:47
      at processticksAndRejections (node:internal/process/task_queues:96:5) {
    uncaught: true,multiple: [ [Error] ]
  }
} TypeError: Cannot read property 'call' of undefined
    at /Users/.../myToken.js:8:47
    at processticksAndRejections (node:internal/process/task_queues:96:5) {
  uncaught: true,multiple: [
    Error: done() called multiple times in hook <Contract: MyToken "before each" hook: before test for "should call a function that depends on a linked library"> of file /Users/.../myToken.js
        at processticksAndRejections (node:internal/process/task_queues:96:5) {
      code: 'ERR_MOCHA_MULTIPLE_DONE',valueType: 'undefined',value: undefined
    }
  ]
}

我不明白发生了什么。我几乎从 tuffle 文档中复制了这段代码，所以一切都应该运行。我错过了什么？

这是我的代码。

const { assert } = require("console");

const MyContract = artifacts.require("My");

contract("MyToken",accounts => {
  it("Should deploy smart contract properly",() => {
    MyContract.deployed()
      .then((instance) => instance.getBalance.call(accounts[0]))
      .then((balance) => {
        assert.equal(
          balance.valueOf(),10000,"10000 wasn't in the first account"
      );
  });
});

it("should call a function that depends on a linked library",() => {
  let my;
  let myBalance; 
  let myEthBalance; 
  return myBalance.deployed()
    .then(instance => {
      my = instance; 
      return my.getBalance.call(accounts[0]);
    })
    .then(outCoinBalance => {
      myBalance = outCoinBalance.toNumber();
      return my.getBalanceInEth.call(accounts[0]);
    })
    .then(outCoinBalanceEth => {
      myEthBalance = outCoinBalanceEth.toNumber();
    })
    .then(() => {
      assert.equal(myEthBalance,2 * myBalance,"Library function returned unexpected function,linkage may be broken"
      );
    });
  });

it("should send coin correctly",() => {
  let my;
  // Get initial balances of first and second account. 
  const account_one = accounts[0];
  const account_two = accounts[1];

  let account_one_starting_balance; 
  let account_two_starting_balance; 
  let account_one_ending_balance; 
  let account_two_ending_balance; 

  const amount = 10; 

  return MyContract.deployed()
    .then(instance => {
      my = instance;
      return my.getBalance.call(account_one);
    })
    .then(balance => {
      account_one_starting_balance = balance.toNumber();
      return my.getBalance.call(account_two);
    })
    .then(balance => {
      account_two_starting_balance = balance.toNumber();
      return my.sendCoin(account_two,amount,{ from: account_one });
    })
    .then(() => my.getBalance.call(account_one))
    .then(balance => {
      account_one_ending_balance = balance.toNumber();
      return my.getBalance.call(account_two);
    })
    .then(balance => {
      account_two_ending_balance = balance.toNumber();

      assert.equal(
        account_one_ending_balance,account_one_starting_balance - amount,"Amount wasn't correctly taken from the sender"
      );
      assert.equal(
        account_two_ending_balance,account_two_starting_balance + amount,"Amount wasn't correctly sent to the receiver"
      );
    });
  });
});```


I have edited some of the names of the variables and the contract names.