Main cleanup of SavingsAccountYear and its test class

removed capitalGainsAmount field and substituted by a method calculation
added ending capital gains without implementation

code as session 9 ending

Author: javierLiarte

scratchpad.txt

@@ -2,4 +2,12 @@ Capital gains
 
 get rid of SavingsAccountYear initializers
 
-clean up _SavingsAccountYearTest
+clean up _SavingsAccountYearTest
+
+Fix primitive obsession
+Make sure next year is setting all variables properly -- need to carry forward capital gains, for example
+Calculate endingCapitalGains()
+
+Consider what to do about withdrawing more than the starting balance -- assert that this is impossible
+fix SavingsAccountYear.newAccount abstraction -- use it or dont?
+We're passing in capitalGainsTaxRate everywhere -- put it in constructor?

src/info/javierliarte/letsPlayTDD/finances/SavingsAccountYear.java

@@ -3,61 +3,68 @@
 public class SavingsAccountYear {
 
 	private int startingBalance = 0;
-	private int capitalGainsAmount = 0;
 	private int interestRate = 0;
 	private int totalWithdrawn = 0;
 	private int startingPrincipal = 0;
 
-	public SavingsAccountYear(int startingBalance, int interestRate) {
-		this.startingBalance = startingBalance;
-		this.interestRate = interestRate;
-	}
-	
 	public SavingsAccountYear(int startingBalance, int startingPrincipal, int interestRate) {
 		this.startingBalance = startingBalance;
-		this.startingPrincipal = startingBalance;
-		this.capitalGainsAmount = startingBalance - startingPrincipal;
+		this.startingPrincipal = startingPrincipal;
 		this.interestRate = interestRate;
 	}
 
 	public int startingBalance() {
 		return startingBalance;
 	}
 
-
 	public int startingPrincipal() {
-		return startingBalance - capitalGainsAmount;
+		return startingPrincipal;
+	}
+
+	public int startingCapitalGains() {
+		return startingBalance - startingPrincipal;
+	}
+
+	public int interestRate() {
+		return interestRate;
+	}
+	
+	public int interestEarned(int capitalGainsTaxRate) {
+		return (startingBalance - totalWithdrawnExceptCapitalGainsTax() - capitalGainsTaxIncurred(capitalGainsTaxRate)) * interestRate / 100;
+	}
+
+	public int totalWithdrawnExceptCapitalGainsTax() {
+		return this.totalWithdrawn;
 	}
 
+	public int totalWithdrawn(int capitalGainsTax) {
+		return totalWithdrawnExceptCapitalGainsTax() + capitalGainsTaxIncurred(capitalGainsTax);
+	}
 
 	public int endingPrincipal() {
-		int result = startingPrincipal() - totalWithdrawn();
+		int result = startingPrincipal() - totalWithdrawnExceptCapitalGainsTax();
 		return Math.max(0, result);
 	}
 
-	public int interestRate() {
-		return interestRate;
+	public int endingCapitalGains() {
+		return 0;
 	}
 
 	public int endingBalance(int capitalGainsTaxRate) {
-		int modifiedStart = startingBalance - totalWithdrawn() - capitalGainsTaxIncurred(capitalGainsTaxRate);
-		return modifiedStart * (100 + interestRate) /100;
+		int modifiedStart = startingBalance - totalWithdrawnExceptCapitalGainsTax() - capitalGainsTaxIncurred(capitalGainsTaxRate);
+		return modifiedStart + interestEarned(capitalGainsTaxRate);
 	}
 
 	public SavingsAccountYear nextYear(int capitalGainsTaxRate) {
-		return new SavingsAccountYear(this.endingBalance(capitalGainsTaxRate),this.interestRate);
+		return new SavingsAccountYear(this.endingBalance(capitalGainsTaxRate), 0, this.interestRate);
 	}
 
 	public void withdraw(int amount) {
 		this.totalWithdrawn += amount;
 	}
 
-	public int totalWithdrawn() {
-		return this.totalWithdrawn;
-	}
-
 	public int capitalGainsWithdrawn() {
-		int result = -1 * (startingPrincipal() - totalWithdrawn());
+		int result = -1 * (startingPrincipal() - totalWithdrawnExceptCapitalGainsTax());
 		return Math.max(0, result);
 	}
 

src/info/javierliarte/letsPlayTDD/finances/_SavingsAccountYearTest.java

@@ -2,6 +2,7 @@
 
 import static org.junit.Assert.*;
 
+import org.junit.Ignore;
 import org.junit.Test;
 
 public class _SavingsAccountYearTest {
@@ -10,68 +11,92 @@ public class _SavingsAccountYearTest {
 	public void startingBalanceMatchesConstructor() {
 		assertEquals(10000, newAccount().startingBalance());
 	}
+	
+	@Test
+	public void startingPrincipalMatchesConstructor() {
+		SavingsAccountYear year = new SavingsAccountYear(10000, 3000, 10);
+		assertEquals("Starting principal", 3000, year.startingPrincipal());
+	}
 
 	@Test
 	public void interestRateMatchesConstructor() {
 		assertEquals(10, newAccount().interestRate());
 	}
-
+	
 	@Test
-	public void endingBalanceAppliesInterestRate() {
-		assertEquals(11000, newAccount().endingBalance(25));
+	public void startingCapitalGainsIsStartingBalanceMinusStartingPrincipal() {
+		SavingsAccountYear year = new SavingsAccountYear(10000, 3000, 10);
+		assertEquals (7000, year.startingCapitalGains());
 	}
 
 	@Test
-	public void nextYearsStartingBalanceEqualsThisYearsEndingBalance() {
-		SavingsAccountYear thisYear = newAccount();
-		assertEquals(thisYear.endingBalance(25), thisYear.nextYear(25)
-				.startingBalance());
+	public void endingPrincipalConsidersWithdrawals() {
+		SavingsAccountYear year = new SavingsAccountYear(10000, 3000, 10);
+		year.withdraw(2000);
+		assertEquals("Ending principal", 1000, year.endingPrincipal());
 	}
 
 	@Test
-	public void nextYearsInterestRateEqualsThisYearsInterestRate() {
-		SavingsAccountYear thisYear = newAccount();
-		assertEquals(thisYear.interestRate(), thisYear.nextYear(25)
-				.interestRate());
+	public void endingPrincipalNeverGoesBelowZero() {
+		SavingsAccountYear year = new SavingsAccountYear(10000, 3000, 10);
+		year.withdraw(4000);
+		assertEquals("ending principal", 0, year.endingPrincipal());
 	}
-
+	
+	@Test
+	public void interestEarnedIsStartingBalanceCombinedWithInterestRate() {
+		SavingsAccountYear year = new SavingsAccountYear(10000, 3000, 10);
+		assertEquals(1000,year.interestEarned(25));
+	}
+	
 	@Test
-	public void withdrawingFundsOccursAtTheBeginningOfTheYear() {
-		SavingsAccountYear year = new SavingsAccountYear(10000, 10);
+	public void withdrawingFundsDoNotEarnInterest() {
+		SavingsAccountYear year = newAccount();
 		year.withdraw(1000);
-		assertEquals(9900, year.endingBalance(25));
+		assertEquals(900, year.interestEarned(25));
 	}
-
+	
 	@Test
-	public void multipleWithdrawalsInAYear() {
-		SavingsAccountYear year = new SavingsAccountYear(10000, 10);
+	public void totalWithdrawnIncludingCapitalGains() {
+		SavingsAccountYear year = new SavingsAccountYear(10000, 0, 10);
 		year.withdraw(1000);
-		year.withdraw(2000);
-		assertEquals(3000, year.totalWithdrawn());
+		assertEquals("capital gains tax", 333, year.capitalGainsTaxIncurred(25));
+		assertEquals("total withdrawn", 1333, year.totalWithdrawn(25));
+	}
+	
+	@Test
+	public void capitalGainsTaxesDoNotEarnInterest() {
+		SavingsAccountYear year = new SavingsAccountYear(10000, 0, 10);
+		year.withdraw(1000);
+		assertEquals("capital gains withdrawn", 1000, year.capitalGainsWithdrawn());
+		assertEquals("capital gains tax", 333, year.capitalGainsTaxIncurred(25));
+//		assertEquals("total withdrawn", 1333, year.totalWithdrawnIncludingCapitalGains());
+		assertEquals("interest earned", 866, year.interestEarned(25));
 	}
 
 	@Test
-	public void principal() {
+	@Ignore
+	public void endingCapitalGainsIncludesInterestEarned() {
 		SavingsAccountYear year = new SavingsAccountYear(10000, 3000, 10);
-		assertEquals("Starting principal", 3000, year.startingPrincipal());
+		assertEquals(7000, year.startingCapitalGains());
+		assertEquals(3000+1000, year.endingCapitalGains());
 	}
 
 	@Test
-	public void endingPrincipal() {
-		SavingsAccountYear year = new SavingsAccountYear(10000, 3000, 10);
-		year.withdraw(2000);
-		assertEquals("Ending principal", 1000, year.endingPrincipal());
+	public void endingBalanceAppliesInterestRate() {
+		assertEquals(11000, newAccount().endingBalance(25));
 	}
 
 	@Test
-	public void endingPrincipalNeverGoesBelowZero() {
-		SavingsAccountYear year = new SavingsAccountYear(10000, 3000, 10);
-		year.withdraw(4000);
-		assertEquals("ending principal", 0, year.endingPrincipal());
+	public void multipleWithdrawalsInAYearAreTotaled() {
+		SavingsAccountYear year = newAccount();
+		year.withdraw(1000);
+		year.withdraw(2000);
+		assertEquals(3000, year.totalWithdrawnExceptCapitalGainsTax());
 	}
 
 	@Test
-	public void capitalGainsWithdrawn() {
+	public void withdrawingMoreThanPrincipalTakesFromCapitalGains() {
 		SavingsAccountYear year = new SavingsAccountYear(10000, 3000, 10);
 		year.withdraw(1000);
 		assertEquals(0, year.capitalGainsWithdrawn());
@@ -95,8 +120,22 @@ public void capitalGainsTaxIsIncludedInEndingBalance() {
 		assertEquals(10000 - 5000 - 666 + 433, year.endingBalance(25));
 	}
 
+	@Test
+	public void nextYearsStartingBalanceEqualsThisYearsEndingBalance() {
+		SavingsAccountYear thisYear = newAccount();
+		assertEquals(thisYear.endingBalance(25), thisYear.nextYear(25)
+				.startingBalance());
+	}
+
+	@Test
+	public void nextYearsInterestRateEqualsThisYearsInterestRate() {
+		SavingsAccountYear thisYear = newAccount();
+		assertEquals(thisYear.interestRate(), thisYear.nextYear(25)
+				.interestRate());
+	}
+
 	private SavingsAccountYear newAccount() {
-		SavingsAccountYear account = new SavingsAccountYear(10000, 10);
+		SavingsAccountYear account = new SavingsAccountYear(10000, 10000, 10);
 		return account;
 	}