roman: add 5 and refactor

roman/roman.go

@@ -4,12 +4,19 @@ import "strings"
 
 func ConvertToRoman(arabic int) string {
 	var converted strings.Builder
-	for i := arabic; i > 0; i-- {
-		if i == 4 {
+	for arabic > 0 {
+		switch {
+		case arabic > 4:
+			converted.WriteString("V")
+			arabic -= 5
+		case arabic > 3:
 			converted.WriteString("IV")
-			break
+			arabic -= 4
+		default:
+			converted.WriteString("I")
+			arabic -= 1
 		}
-		converted.WriteString("I")
 	}
+
 	return converted.String()
 }

roman/roman_test.go

@@ -12,6 +12,7 @@ func TestRomanNemerals(t *testing.T) {
 		{"2 gets converted to II", 2, "II"},
 		{"3 gets converted to III", 3, "III"},
 		{"4 gets converted to IV", 4, "IV"},
+		{"5 gets converted to V", 5, "V"},
 	}
 	for _, test := range cases {
 		t.Run(test.Description, func(t *testing.T) {