How to fix "No events were emitted"

Question

I have been following the instructions in the Dapp university tutorial. But I am using Windows 10, Dapp University is Mac.

I downloaded this truffle with smart contract ERC20 from Dapp university.
Reference: https://github.com/dappuniversity/token_sale

This is the reference of the solidity (I only rename the file to bruce.sol) https://github.com/dappuniversity/token_sale/blob/master/contracts/DappToken.sol

Where I run truffle test --network development this displays:

Using network 'local'.



  Contract: BruceToken
    √ initializes the contract with the correct values
    √ allocates the initial supply upon deployment
    1) transfers token ownership
    > No events were emitted
    2) approves tokens for delegated transfer
    > No events were emitted
    3) handles delegated token transfers
    > No events were emitted

  Contract: BruceTokenSale
    √ initializes the contract with the correct values
    4) facilitates token buying

    Events emitted during test:
    ---------------------------

    Transfer(_from: <indexed>, _to: <indexed>, _value: 750000)

    ---------------------------
    5) ends token sale
    > No events were emitted


  3 passing (32s)
  5 failing

  1) Contract: BruceToken
       transfers token ownership:
     AssertionError: error message must contain revert
      at test\BruceToken.js:39:7
      at <anonymous>
      at process._tickCallback (internal/process/next_tick.js:188:7)

  2) Contract: BruceToken
       approves tokens for delegated transfer:
     TypeError: Cannot read property 'call' of undefined
      at test\BruceToken.js:62:36
      at <anonymous>
      at process._tickCallback (internal/process/next_tick.js:188:7)

  3) Contract: BruceToken
       handles delegated token transfers:
     AssertionError: cannot transfer value larger than approved amount
      at test\BruceToken.js:97:7
      at <anonymous>
      at process._tickCallback (internal/process/next_tick.js:188:7)

  4) Contract: BruceTokenSale
       facilitates token buying:
     AssertionError: cannot purchase more tokens than available
      at test\BruceTokenSale.js:61:7
      at <anonymous>
      at process._tickCallback (internal/process/next_tick.js:188:7)

  5) Contract: BruceTokenSale
       ends token sale:

      returns all unsold bruce tokens to admin
      + expected - actual

      -250000
      +999990

      at test\BruceTokenSale.js:82:14
      at <anonymous>
      at process._tickCallback (internal/process/next_tick.js:188:7)



PS D:\Blvnp\DappUniversity\brucev2token_sale-master>
PS D:\Blvnp\DappUniversity\brucev2token_sale-master>
PS D:\Blvnp\DappUniversity\brucev2token_sale-master>
PS D:\Blvnp\DappUniversity\brucev2token_sale-master>
PS D:\Blvnp\DappUniversity\brucev2token_sale-master> ^C
PS D:\Blvnp\DappUniversity\brucev2token_sale-master> truffle test --network development
Could not connect to your Ethereum client. Please check that your Ethereum client:
    - is running
    - is accepting RPC connections (i.e., "--rpc" option is used in geth)
    - is accessible over the network
    - is properly configured in your Truffle configuration file (truffle.js)

PS D:\Blvnp\DappUniversity\brucev2token_sale-master> truffle test --network development
Using network 'development'.



  Contract: BruceToken
    √ initializes the contract with the correct values (165ms)
    √ allocates the initial supply upon deployment (44ms)
    √ transfers token ownership (214ms)
    1) approves tokens for delegated transfer
    > No events were emitted
    2) handles delegated token transfers

    Events emitted during test:
    ---------------------------

    Transfer(_from: <indexed>, _to: <indexed>, _value: 100)

    ---------------------------

  Contract: BruceTokenSale
    √ initializes the contract with the correct values (41ms)
    √ facilitates token buying (401ms)
    √ ends token sale (501ms)


  6 passing (2s)
  2 failing

  1) Contract: BruceToken
       approves tokens for delegated transfer:
     TypeError: Cannot read property 'call' of undefined
      at test\BruceToken.js:62:36
      at <anonymous>
      at process._tickCallback (internal/process/next_tick.js:188:7)

  2) Contract: BruceToken
       handles delegated token transfers:
     AssertionError: cannot transfer value larger than approved amount
      at test\BruceToken.js:97:7
      at <anonymous>
      at process._tickCallback (internal/process/next_tick.js:188:7)

Now this is my truffle.js:

module.exports = {
  networks: {
    development: {
      host: "127.0.0.1",
      port: 7545,
      network_id: "*"
    },
    local: {
      host: "192.168.*.***",
      port: 1201,
      gas: 2000000,
      gasPrice: 10000000000,
      network_id: "*"
    }
  }
};

Answer 1

No events emitted is not a bug. So you can't fix it.

When a test fails, Truffle shows you which events emitted during the test so you can debug easily.

Answer 2

If you arrived here looking for a way to print the events emitted during your tests, you can do this with the --show-events flag:

truffle test --show-events

Answer 3

My issue was that my event was called "TestEvent" and for this reason it was not firing. I renamed it to something else and it fired. Not sure why this but wasted half an hour scratching my head cause of this...

Maybe this is some sort of expected truffle behaviour when the event is named "TestEvent"?

Answer 4

I had the very same problem. 1.5 hours later, I realized that I had copied and pasted

let DappToken = artifacts.require('./DappTokenSale.sol');
let DappTokenSale = artifacts.require('./DappTokenSale.sol');

The error was then hidden in the error stack and was something along the lines of "tokenInstance.transfer() is not a function."

I corrected the typo:

let DappToken = artifacts.require('./DappToken.sol');

and then it worked.

Answer 5

Check to see that your assert statement is actually valid. In my case, I was asserting that two arrays were equal, however, Comparing the values in the array worked.