Credit Module

Spring Boot backend Loan API for a bank so that their employees can create, list and pay loans for their customers. Storing data on in-memory H2 Database.

• Credit Module
  • Technical Design
    • TODO List
    • Table Design
    • Endpoints
    • Potential Test Cases
  • How to use
  • Additional notes

Technical Design

TODO List

• listLoans: OK
• listInstallment: OK
• payLoan: OK
• CreateLoan: OK
• Admin login: OK
• Bonus 1: NOT OK
• Bonus 2: OK

Table Design

• Customer: id, name, surname, creditLimit, usedCreditLimit
• Loan: id, customerId, loanAmount, numberOfInstallment, createDate, isPaid
• LoanInstallment: id, loanId, amount, paidAmount, dueDate, paymentDate, isPaid

Endpoints

• createLoan

  • Request:
    • long customerId
    • Double amount
    • Double interestRate (between 0.1 – 0.5)
    • int numberOfInstallments (6, 9, 12, 24)
  • Response
    • int responseCode: (0: successfully created, etc.)
    • String responseDescription

• listLoans

  • Request:
    • long customerId
    • String loanStatus (String Enum: PAID, UNPAID, ALL)
  • Response
    • int responseCode: (0: successfully created, etc.)
    • String responseDescription
    • List:
      • String loanStatus
      • long loanId (used for differentiate loans and inquiring loan's installments.)
      • Double loanAmount
      • int numberOfInstallments

• listInstallment

  • Request:
    • long customerId
    • long loanId
  • Response:
    • int responseCode: (0: successfully created, etc.)
    • String responseDescription
    • List
      • long loanId
      • Double Amount
      • String dueDate
      • String paymentDate
      • Boolean isPaid

• payLoan

  • Request
    • long customerId
    • İnt loanId
    • Double Amount
  • Response
    • int responseCode: (0: successfully created, etc.)
    • String responseDescription
    • int countOfPaidInstallments
    • Double paidAmount (amount - remaining)
    • Boolean loanClosed

Potential Test Cases

• createLoan
  • Unit:
    • Limit not sufficient case
    • Create loan successfully
      • Verify usedCreditLimit update on Customer table
      • Verify insert to Loan Table
      • Verify insert to LoanInstallment Table
  • Integration:
    • Number of installments check
    • Interest rate check
    • Customer not found
• listLoans
  • Unit:
    • Customer not found
    • Matching loan not found
  • Integration:
    • Invalid loan status
• listInstallment
  • Unit:
    • Limit not sufficient case
  • Integration:
    • Loan not found
    • Customer not found
• payLoan
  • Unit:
    • Not paid any installments
      • Verify no update on Customer, Loan, LoanInstallment tables.
    • payAll
      • Verify update on Customer, Loan, LoanInstallment tables.
    • paySomeWithRemainderAmountAfter
      • Verify update on Customer, LoanInstallment tables.
    • paySomeUpTo3Months
      • Verify update on Customer, LoanInstallment tables.
  • Integration:
    • Loan not found
    • Customer not found

How to use

user: admin password: password

• listLoans (GET)
  • Endpoint: http://localhost:8080/listLoans?customerId=1&loanStatus=ALL
  • Loanstatus: ‘ALL’, ‘PAID’, ‘UNPAID’
• listInstallment (GET)
  • Endpoint: http://localhost:8080/listInstallments?customerId=1&loanId=1234
• createLoan (POST)
  • http://localhost:8080/createLoan
• payLoan (POST)
  • http://localhost:8080/payLoan

For tests Postman Collection in the main directory can be used.

Additional notes