Assignment finished with TDD approach.

src/RomanNumerals.java

@@ -1,8 +1,60 @@
 
 public class RomanNumerals {
-	public int convertToInteger(String romanNum) {
-		// To be Implemented
-		return 0;
-
+
+	public int convertToInteger(String str) {
+		int result = 0;	
+		if(str==null||str.isEmpty()||!(isValid(str))){
+			return 0;
+		}
+		else{
+		for (int i = 0; i < str.length(); i++){
+
+			int s1 = getIntegerValue(str.charAt(i));
+			if (i + 1 < str.length()){
+
+				int s2 = getIntegerValue(str.charAt(i + 1));
+				if (s1 >= s2){
+					result = result + s1;
+				} else 
+				{
+					result = result + s2 - s1;
+					i++; 
+				}
+			} else {
+				result = result + s1;
+				i++;
+			}
+		}
+		}
+		return result;
+
+	}
+
+	public int getIntegerValue(char r) {
+		if (r == 'I')
+			return 1;
+		if (r == 'V')
+			return 5;
+		if (r == 'X')
+			return 10;
+		if (r == 'L')
+			return 50;
+		if (r == 'C')
+			return 100;
+		if (r == 'D')
+			return 500;
+		if (r == 'M')
+			return 1000;
+		return -1;
+	}
+	public boolean isValid(String str){
+		if(str.matches("IIII")||str.matches("XXXX")||str.matches("CCCC")||str.matches("MMMM")){
+			return false;
+		}
+		if(str.matches("DD")||str.matches("LL")||str.matches("VV")){
+			return false;
+		}
+		return true;
 	}
+
 }

tests/TestRomanNumerals.java

@@ -1,12 +1,37 @@
 import static org.junit.Assert.*;
-
 import org.junit.Test;
 
 public class TestRomanNumerals {
+	@Test
+	public void testUnitExpression() {
+		String roman = "VI";
+		RomanNumerals rn = new RomanNumerals();
+		assertEquals("Unit conversion fails", 6, rn.convertToInteger(roman));
+
+	}
 
 	@Test
-	public void test() {
-		fail("Not yet implemented");
+	public void testTenExpression() {
+		String roman = "XII";
+		RomanNumerals rn = new RomanNumerals();
+		assertEquals("Ten conversion fails", 12, rn.convertToInteger(roman));
+
+	}
+
+	@Test
+	public void testHunderedExpression() {
+		String roman = "CII";
+		RomanNumerals rn = new RomanNumerals();
+		assertEquals("Hundered conversion fails", 102, rn.convertToInteger(roman));
+
+	}
+
+	@Test
+	public void testThousandExpression() {
+		String roman = "MCMLXXXIV";
+		RomanNumerals rn = new RomanNumerals();
+		assertEquals("Thousand conversion fails", 1984, rn.convertToInteger(roman));
+
 	}
 
 }