ex-2: extract historyLengthFactor out of Rating.voyageAndHistoryLengthFactor

Author: kaiosilveira

src/using-polymorphism-for-variation/rating/index.js

@@ -36,11 +36,15 @@ export class Rating {
 
   get voyageAndHistoryLengthFactor() {
     let result = 0;
-    if (this.history.length > 8) result += 1;
+    result += this.historyLengthFactor;
     if (this.voyage.length > 14) result -= 1;
     return result;
   }
 
+  get historyLengthFactor() {
+    return this.history.length > 8 ? 1 : 0;
+  }
+
   get hasChinaHistory() {
     return this.history.some(v => 'china' === v.zone);
   }

src/using-polymorphism-for-variation/rating/index.test.js

@@ -140,6 +140,20 @@ describe('Rating', () => {
       expect(rating.voyageAndHistoryLengthFactor).toEqual(-1);
     });
   });
+
+  describe('historyLengthFactor', () => {
+    it('should return 0 if history length is less than 8', () => {
+      const history = Array.from({ length: 7 }, () => latamVoyage);
+      const rating = new Rating(latamVoyage, history);
+      expect(rating.historyLengthFactor).toEqual(0);
+    });
+
+    it('should return 1 if history length is more than 8', () => {
+      const history = Array.from({ length: 9 }, () => latamVoyage);
+      const rating = new Rating(latamVoyage, history);
+      expect(rating.historyLengthFactor).toEqual(1);
+    });
+  });
 });
 
 describe('ExperiencedChinaRating', () => {