Testing a Domain Entity with Unit Tests

We will start by looking at a domain entity at the center of our architecture. Let's recall the Account entity from Chapter 4, Implementing a Use Case. The state of an Account consists of a balance the account had at a certain point in the past (the baseline balance) and a list of deposits and withdrawals (activities) since then. We now want to verify that the withdraw() method works as expected:

class AccountTest {

  @Test

  void withdrawalSucceeds() {

    AccountId accountId = new AccountId(1L);

    Account account = defaultAccount()

        .withAccountId(accountId)

        .withBaselineBalance(Money.of(555L))

        .withActivityWindow(new ActivityWindow(

            defaultActivity()

     ...