work on fixing interest calculation for declining balance loans.

mifosng-provider/src/test/java/org/mifosng/platform/loanschedule/domain/DecliningBalanceMethodLoanScheduleGeneratorTest.java

@@ -0,0 +1,112 @@
+package org.mifosng.platform.loanschedule.domain;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.*;
+
+import java.util.List;
+
+import org.hamcrest.Matcher;
+import org.joda.time.LocalDate;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mifosng.platform.api.data.CurrencyData;
+import org.mifosng.platform.api.data.LoanSchedule;
+import org.mifosng.platform.api.data.ScheduledLoanInstallment;
+import org.mifosng.platform.loan.domain.LoanProductRelatedDetail;
+import org.mifosng.platform.loan.domain.PeriodFrequencyType;
+import org.mockito.runners.MockitoJUnitRunner;
+
+@RunWith(MockitoJUnitRunner.class)
+public class DecliningBalanceMethodLoanScheduleGeneratorTest {
+
+	// class under test
+	private DecliningBalanceMethodLoanScheduleGenerator decliningBalanceGenerator;
+	
+	// test doubles
+	private CurrencyData currencyData = null;
+	private LoanProductRelatedDetail loanScheduleInfo = null;
+	
+	@Before
+	public void setupForEachTest() {
+		currencyData = new CurrencyData("USD", "US Dollar", 2, "$", "currency.USD");
+		
+		decliningBalanceGenerator = new DecliningBalanceMethodLoanScheduleGenerator();
+	}
+	
+	@Test
+	public void givenEqualInstallmentAmortisationShouldCalculatePaymentPerInstallmentUsingPmtFunctionAndDerivePrincipalAndInterestComponents() {
+		
+		// setup
+		Integer loanTermFrequency = 12;
+		PeriodFrequencyType loanTermFrequencyType = PeriodFrequencyType.MONTHS;
+		loanScheduleInfo = LoanProductRelatedDetailTestHelper.createSettingsForEqualInstallmentAmortizationQuarterly();
+		
+		LocalDate disbursementDate = new LocalDate(2011, 1, 11);
+		LocalDate firstRepaymentDate = new LocalDate(2011, 5, 1);
+		LocalDate interestCalculatedFrom = new LocalDate(2011, 2, 1);
+		
+		// pre assertions
+		assertThat(loanTermFrequency, is(loanScheduleInfo.getNumberOfRepayments() * loanScheduleInfo.getRepayEvery()));
+		assertThat(loanTermFrequencyType, is(loanScheduleInfo.getRepaymentPeriodFrequencyType()));
+		
+		// exercise test
+		LoanSchedule schedule = decliningBalanceGenerator.generate(loanScheduleInfo, loanTermFrequency, loanTermFrequencyType, 
+				disbursementDate, firstRepaymentDate, interestCalculatedFrom, currencyData);
+		
+		// verification (post assertions)
+		given(schedule).assertHasInstallmentSizeOf(4);
+		given(schedule).assertTotalPaymentDueOf(1, is("57718.30")).assertInterestDueComponentOf(1, is("12000.00")).assertPrincipalDueComponentOf(1, is("45718.30"));
+		given(schedule).assertTotalPaymentDueOf(2, is("57718.30")).assertInterestDueComponentOf(2, is("9256.90")).assertPrincipalDueComponentOf(2, is("48461.40"));
+		given(schedule).assertTotalPaymentDueOf(3, is("57718.30")).assertInterestDueComponentOf(3, is("6349.22")).assertPrincipalDueComponentOf(3, is("51369.08"));
+		given(schedule).assertTotalPaymentDueOf(4, is("57718.30")).assertInterestDueComponentOf(4, is("3267.08")).assertPrincipalDueComponentOf(4, is("54451.22"));
+	}
+	
+	private LoanScheduleAssertionBuilder given(final LoanSchedule schedule) {
+		return new LoanScheduleAssertionBuilder(schedule);
+	}
+	
+	private class LoanScheduleAssertionBuilder {
+		
+		private final LoanSchedule schedule;
+
+		public LoanScheduleAssertionBuilder(final LoanSchedule schedule) {
+			this.schedule = schedule;
+		}
+		
+		public LoanScheduleAssertionBuilder assertPrincipalDueComponentOf(final int installmentNumber, Matcher<String> matchesExpectedAmount) {
+			final Integer installmentIndex = installmentNumber -1;
+			List<ScheduledLoanInstallment> repaymentInstallments = schedule.getScheduledLoanInstallments();
+			ScheduledLoanInstallment repaymentInstallment = repaymentInstallments.get(installmentIndex);
+			
+			assertThat("Expected principal due component for installment " + installmentNumber + " is wrong: ", 
+					repaymentInstallment.getPrincipalDue().toString(), matchesExpectedAmount);
+			return this;
+		}
+
+		public LoanScheduleAssertionBuilder assertInterestDueComponentOf(final int installmentNumber, Matcher<String> matchesExpectedAmount) {
+			final Integer installmentIndex = installmentNumber -1;
+			List<ScheduledLoanInstallment> repaymentInstallments = schedule.getScheduledLoanInstallments();
+			ScheduledLoanInstallment repaymentInstallment = repaymentInstallments.get(installmentIndex);
+			
+			assertThat("Expected interest due component for installment " + installmentNumber + " is wrong: ", 
+					repaymentInstallment.getInterestDue().toString(), matchesExpectedAmount);
+			return this;
+		}
+
+		public LoanScheduleAssertionBuilder assertTotalPaymentDueOf(final int installmentNumber, Matcher<String> matchesExpectedAmount) {
+			final Integer installmentIndex = installmentNumber -1;
+			List<ScheduledLoanInstallment> repaymentInstallments = schedule.getScheduledLoanInstallments();
+			ScheduledLoanInstallment repaymentInstallment = repaymentInstallments.get(installmentIndex);
+			
+			assertThat("Expected total payment for installment " + installmentNumber + " is wrong: ", 
+					repaymentInstallment.getTotalInstallmentDue().toString(), matchesExpectedAmount);
+			return this;
+		}
+
+		public LoanScheduleAssertionBuilder assertHasInstallmentSizeOf(int expectedInstallmentSize) {
+			assertThat("Expected number of installments is wrong: ", schedule.getScheduledLoanInstallments().size(), is(expectedInstallmentSize));
+			return this;
+		}
+	}
+}

mifosng-provider/src/test/java/org/mifosng/platform/loanschedule/domain/LoanProductRelatedDetailTestHelper.java

@@ -0,0 +1,41 @@
+package org.mifosng.platform.loanschedule.domain;
+
+import java.math.BigDecimal;
+
+import org.mifosng.platform.currency.domain.MonetaryCurrency;
+import org.mifosng.platform.loan.domain.AmortizationMethod;
+import org.mifosng.platform.loan.domain.InterestCalculationPeriodMethod;
+import org.mifosng.platform.loan.domain.InterestMethod;
+import org.mifosng.platform.loan.domain.LoanProductRelatedDetail;
+import org.mifosng.platform.loan.domain.MonetaryCurrencyBuilder;
+import org.mifosng.platform.loan.domain.PeriodFrequencyType;
+
+/**
+ * This class is used to keep in one place configurations for setting up {@link LoanProductRelatedDetail} object used in {@link LoanScheduleGenerator}'s
+ */
+public class LoanProductRelatedDetailTestHelper {
+
+	public static LoanProductRelatedDetail createSettingsForEqualInstallmentAmortizationQuarterly() {
+		MonetaryCurrency currency = new MonetaryCurrencyBuilder().withCode("USD").withDigitsAfterDecimal(2).build();
+		BigDecimal defaultPrincipal = BigDecimal.valueOf(Double.valueOf("200000"));
+		
+		// 2% per month, 24% per year
+		BigDecimal defaultNominalInterestRatePerPeriod = BigDecimal.valueOf(Double.valueOf("2"));  
+		PeriodFrequencyType interestPeriodFrequencyType = PeriodFrequencyType.MONTHS;
+		BigDecimal defaultAnnualNominalInterestRate = BigDecimal.valueOf(Double.valueOf("24"));
+		
+		InterestMethod interestMethod = InterestMethod.DECLINING_BALANCE;
+		InterestCalculationPeriodMethod interestCalculationPeriodMethod = InterestCalculationPeriodMethod.SAME_AS_REPAYMENT_PERIOD;
+		Integer repayEvery = Integer.valueOf(3);
+		PeriodFrequencyType repaymentFrequencyType = PeriodFrequencyType.MONTHS;
+		
+		Integer defaultNumberOfRepayments = Integer.valueOf(4);
+		AmortizationMethod amortizationMethod = AmortizationMethod.EQUAL_INSTALLMENTS;
+		
+		BigDecimal inArrearsTolerance = BigDecimal.ZERO;
+		
+		return new LoanProductRelatedDetail(currency, defaultPrincipal, defaultNominalInterestRatePerPeriod, 
+				interestPeriodFrequencyType, defaultAnnualNominalInterestRate, interestMethod, 
+				interestCalculationPeriodMethod, repayEvery, repaymentFrequencyType, defaultNumberOfRepayments, amortizationMethod, inArrearsTolerance);
+	}
+}