Agile Software Development
Principles, Pattern, and Practices

The Payroll System

This is an attempt to apply Clean Architecture / DDD to the The Payroll System case study from the Agile Software Development book while using typescript.

Features

You can see the features in Cucumber here.

Rudimentary Specification of the Payroll System [From the book]

The following are some of the notes we took while conversing with our customer.

This system consists of a database of the employees in the company and their associated data, such as time cards. The system must pay each employee. Employees must be paid the correct amount, on time, by the method that they specify. Also, various deductions must be taken from their pay.

• Some employees work by the hour. They are paid an hourly rate that is one of the fields in their employee record. They submit daily time cards that record the date and the number of hours worked. If they work more than 8 hours per day, they are paid 1.5 times their normal rate for those extra hours. They are paid every Friday.
• Some employees are paid a flat salary. They are paid on the last working day of the month. Their monthly salary is one of the fields in their employee record.
• Some of the salaried employees are also paid a commission based on their sales. They submit sales receipts that record the date and the amount of the sale. Their commission rate is a field in their employee record. They are paid every other Friday.
• Employees can select their method of payment. They may have their paychecks mailed to the postal address of their choice; they may have their paychecks held for pickup by the Paymaster; or they can request that their paychecks be directly deposited into the bank account of their choice.
• Some employees belong to the union. Their employee record has a field for the weekly dues rate. Their dues must be deducted from their pay. Also, the union may assess service charges against individual union members from time to time. These service charges are submitted by the union on a weekly basis and must be deducted from the appropriate employee’s next pay amount.
• The payroll application will run once each working day and pay the appropriate employees on that day. The system will be told to what date the employees are to be paid, so it will calculate payments from the last time the employee was paid up to the specified date.

Exercise

Before you continue, you might find it instructive to design the payroll system on your own, now. You might want to sketch some initial UML diagrams. Better yet, you might want to implement the first few use cases test-first. Apply the principles and practices we’ve learned so far, and try to create a balanced and healthy design.

If you are going to do this, then take a look at the use cases that follow. Otherwise skip them, they’ll be presented again in the Payroll chapter.

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Use Case 1: Add New Employee

A new employee is added by the receipt of an AddEmp transaction. This transaction contains the employee’s name, address, and assigned employee number. The transaction has the following three forms:

AddEmp <EmpID> “<name>” “<address>” H <hourly—rate>
AddEmp <EmpID> “<name>” “<address>” S <month1y—sa1ary>
AddEmp <EmpID> “<name>" “<address>” C <monthly-salary> <commission—rate>

The employee record is created with its fields assigned appropriately.

Alternative:

An error in the transaction structure

If the transaction structure is inappropriate, it is printed out in an error message, and no action is taken.

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Use Case 2: Deleting an Employee

Employees are deleted when a DelEmp transaction is received. The form of this transaction is as follows:

DelEmp <EmpID>

When this transaction is received, the appropriate employee record is deleted.

Alternative:

Invalid or unknown EmpID

If the <EmpID> field is not structured correctly, or if it does not refer to a valid employee record, then the transaction is printed with an error message, and no other action is taken.

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Use Case 3: Post a Time Card

Upon receipt of a TimeCard transaction, the system will create a time-card record and associate it with the appropriate employee record.

TimeCard <Emp1d> <date> <hours>

Alternative 1:

The selected employee is not hourly

The system will print an appropriate error message and take no further action.

Alternative 2:

An error in the transaction structure

The system will print an appropriate error message and take no further action.

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Use Case 4: Posting a Sales Receipt

Upon receipt of the SalesReceipt transaction, the system will create a new sales-receipt record and associate it with the appropriate commissioned employee.

SalesReceipt <EmpID> <date> <amount>

Alternative 1:

The selected employee is not commissioned

The system will print an appropriate error message and take no further action.

Alternative 2:

An error in the transaction structure

The system will print an appropriate error message and take no further action.

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Use Case 5: Posting a Union Service Charge

Upon receipt of this transaction, the system will create a service-charge record and associate it with the appropriate union member.

ServiceCharge <memberID> <amount>

Alternative:

Poorly formed transaction

If the transaction is not well formed or if the <memberID> does not refer to an existing union member, then the transaction is printed with an appropriate error message.

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Use Case 6: Changing Employee Details

Upon receipt of this transaction, the system will alter one of the details of the appropriate employee record. There are several possible variations to this transaction.

ChgEmp <EmpID> Name <name>                         Change Employee Name
ChgEmp <EmpID> Address <address>                   Change Employee Address
ChgEmp <EmpID> Hourly <hourlyRate>                 Change to Hourly
ChgEmp <EmpID> Salaried <salary>                   Change to Salaried
ChgEmp <EmpID> Commissioned <salary> <rate>        Change to Commissioned
ChgEmp <EmpID> Hold                                Hold Paycheck
ChgEmp <EmpID> Direct <bank> <account>             Direct Deposit
ChgEmp <EmpID> Mail <address>                      Mail Paycheck
ChgEmp <EmpID> Member <memberID> Dues <rate>       Put Employee in Union
ChgEmp <EmpID> NoMember                            Remove Employee from Union

Alternative:

Transaction Errors

If the structure of the transaction is improper or <EmpID> does not refer to a real employee or <memberID> already refers to a member, then print a suitable error and take no further action.

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Use Case 7: Run the Payroll for Today

Upon receipt of the Payday transaction, the system finds all those employees that should be paid upon the specified date. The system then determines how much they are owed and pays them according to their selected payment method.

Payday <date>