### Question:
DesignatorToAccountIdentifierMapper { Optional<AccountAssignment> mapToCaseAccountAssignment(final @Nonnull String accountDesignator) { return caseAccountAssignments.stream().map(CaseMapper::mapAccountAssignmentEntity) .filter(x -> x.getDesignator().equals(accountDesignator)) .findFirst(); } DesignatorToAccountIdentifierMapper(final @Nonnull DataContextOfAction dataContextOfAction);   DesignatorToAccountIdentifierMapper(
      final @Nonnull Set<ProductAccountAssignmentEntity> productAccountAssignments,
      final @Nonnull Set<CaseAccountAssignmentEntity> caseAccountAssignments,
      final @Nonnull List<AccountAssignment> oneTimeAccountAssignments); Optional<String> map(final @Nonnull String accountDesignator); String mapOrThrow(final @Nonnull String accountDesignator); Stream<GroupNeedingLedger> getGroupsNeedingLedgers(); Stream<AccountAssignment> getLedgersNeedingAccounts();  }### Answer:
@Test public void mapToCaseAccountAssignment() { final Optional<AccountAssignment> ret = testSubject.mapToCaseAccountAssignment(AccountDesignators.CUSTOMER_LOAN_GROUP); Assert.assertEquals(testCase.expectedCaseAccountAssignmentMappingForCustomerLoanGroup, ret); }