Function: transferFrom(address _sender, address _recipient, uint256 _amount)

Allows transferring tokens from an account to another.

Inputs

• _sender

  • Control: Fully controlled by the caller.

  • Constraints: None --- only checked that msg.sender has enough allowance for the particular _sender.

  • Impact: The account that will send the tokens.

• _recipient

  • Control: Fully controlled by the caller.

  • Constraints: None.

  • Impact: The account that will receive the tokens.

• _amount

  • Control: Fully controlled by the caller.

  • Constraints: Ensured that msg.sender has enough allowance for the particular _sender.

  • Impact: The amount of tokens to be transferred.

Branches and code coverage (including function calls)

Intended branches

• Assumes no malicious intent on behalf of the handler.

  Test coverage

• If msg.sender is the handler, do not check allowance.

  Test coverage

• Checks that the _sender has enough balance. Ensured in _transfer.

  Test coverage

• Checks that the _recipient is not the zero address. Ensured in _transfer.

  Test coverage

• Checks that the _amount is greater than zero. Ensured in _transfer.

  Test coverage

• Decreases the balances for the _sender. Ensured in _transfer.

  Test coverage

• Increases the balances for the _recipient. Ensured in _transfer.

  Test coverage

• Decreases the allowance of _sender for msg.sender by _amount. Ensured in _approve.

  Test coverage

• Ensures enough allowance for msg.sender has been granted by _sender.

  Test coverage

Negative behavior

• Should not allow tranferring more tokens than the _sender has, even if the allowance is greater than the balance.

  Negative test

• Should not allow transferring more tokens than the allowance granted by the _sender.

  Negative test