create Account Repository for AccountServiceTest mocked

src/test/java/hs/fulda/de/ci/exam/project/AccountServiceTest.java

@@ -21,10 +21,18 @@ public class AccountServiceTest {
 
     @Before
     public void setup() {
+        accountRepository = createAccountRepository();
         passwordEncoder = createPasswordEncoder();
         accountService = new AccountService(accountRepository, passwordEncoder);
     }
 
+    private AccountRepository createAccountRepository() {
+        AccountRepository mock = mock(AccountRepository.class);
+        when(mock.findById(ENABLED_USER.getId())).thenReturn(ENABLED_USER);
+        when(mock.findById(DISABLED_USER.getId())).thenReturn(DISABLED_USER);
+        return mock;
+    }
+
     private PasswordEncoder createPasswordEncoder() {
         PasswordEncoder mock = mock(PasswordEncoder.class);
         when(mock.encode(anyString())).thenReturn("any password hash");