diff --git a/index.js b/index.js
index 525c9de1..d1ebc9af 100644
--- a/index.js
+++ b/index.js
@@ -8,15 +8,23 @@ const drugs = [
   new Drug("Magic Pill", 15, 40)
 ];
 const trial = new Pharmacy(drugs);
-
 const log = [];
 
 for (let elapsedDays = 0; elapsedDays < 30; elapsedDays++) {
   log.push(JSON.stringify(trial.updateBenefitValue()));
 }
 
+const stringLog = log.toString();
+let multipleLineLog = "";
+for(let i = 0; i < stringLog.length; i++){
+  multipleLineLog += stringLog[i];
+  if(stringLog[i]== ']') {
+    multipleLineLog += "\n";
+  }
+}
+
 /* eslint-disable no-console */
-fs.writeFile("output.txt", log.toString(), err => {
+fs.writeFile("output.txt", multipleLineLog, err => {
   if (err) {
     console.log("error");
   } else {
diff --git a/pharmacy.js b/pharmacy.js
index cda44c41..4dbd5f56 100644
--- a/pharmacy.js
+++ b/pharmacy.js
@@ -12,55 +12,62 @@ export class Pharmacy {
   }
   updateBenefitValue() {
     for (var i = 0; i < this.drugs.length; i++) {
-      if (
-        this.drugs[i].name != "Herbal Tea" &&
-        this.drugs[i].name != "Fervex"
-      ) {
-        if (this.drugs[i].benefit > 0) {
-          if (this.drugs[i].name != "Magic Pill") {
-            this.drugs[i].benefit = this.drugs[i].benefit - 1;
-          }
-        }
-      } else {
-        if (this.drugs[i].benefit < 50) {
-          this.drugs[i].benefit = this.drugs[i].benefit + 1;
-          if (this.drugs[i].name == "Fervex") {
-            if (this.drugs[i].expiresIn < 11) {
-              if (this.drugs[i].benefit < 50) {
-                this.drugs[i].benefit = this.drugs[i].benefit + 1;
-              }
-            }
-            if (this.drugs[i].expiresIn < 6) {
-              if (this.drugs[i].benefit < 50) {
-                this.drugs[i].benefit = this.drugs[i].benefit + 1;
-              }
-            }
-          }
-        }
+      const drugName = this.drugs[i].name;
+      if(drugName == "Magic Pill") {
+          continue;
       }
-      if (this.drugs[i].name != "Magic Pill") {
-        this.drugs[i].expiresIn = this.drugs[i].expiresIn - 1;
-      }
-      if (this.drugs[i].expiresIn < 0) {
-        if (this.drugs[i].name != "Herbal Tea") {
-          if (this.drugs[i].name != "Fervex") {
-            if (this.drugs[i].benefit > 0) {
-              if (this.drugs[i].name != "Magic Pill") {
-                this.drugs[i].benefit = this.drugs[i].benefit - 1;
+      // expiration evolution
+      this.drugs[i].expiresIn = this.drugs[i].expiresIn - 1;
+      const expirationTime = this.drugs[i].expiresIn;
+      let evolutionValue = (expirationTime < 0)? 2:1;
+      let evolutionSign = -1;
+      let evolutionCoeff = 1;
+      let stillWorthCoeff = 1;
+      
+      switch (drugName) {
+          case 'Herbal Tea':
+              evolutionSign = 1;
+              break;
+
+          case 'Fervex':
+              switch (true) {
+                  case (expirationTime < 0):
+                      stillWorthCoeff = 0;
+                      break;
+                  case (expirationTime < 6):
+                      evolutionValue = 3;
+                      break;
+                  case (expirationTime < 11):
+                      evolutionValue = 2;
+                      break;
+                  default:
+                      break;
               }
-            }
-          } else {
-            this.drugs[i].benefit =
-              this.drugs[i].benefit - this.drugs[i].benefit;
-          }
-        } else {
-          if (this.drugs[i].benefit < 50) {
-            this.drugs[i].benefit = this.drugs[i].benefit + 1;
-          }
+              evolutionSign = 1;
+              break;
+
+          case 'Dafalgan':
+              evolutionCoeff = 2;
+              break;
+
+          default:
+              break;
         }
-      }
+        // calculate benefit evolution
+        this.drugs[i].benefit = (this.drugs[i].benefit + (evolutionValue * evolutionSign * evolutionCoeff)) * stillWorthCoeff;
+
+        // general rules
+        // the benefit of an item is never more than 50
+        if(this.drugs[i].benefit > 50) {
+          this.drugs[i].benefit = 50;
+        }
+        // the benefit of an item is never less than 0
+        if(this.drugs[i].benefit < 0) {
+          this.drugs[i].benefit = 0;
+        }
+        
     }
 
     return this.drugs;
   }
-}
+}
\ No newline at end of file
diff --git a/pharmacy.test.js b/pharmacy.test.js
index f0925fc1..b5c2ecc8 100644
--- a/pharmacy.test.js
+++ b/pharmacy.test.js
@@ -1,9 +1,112 @@
 import { Drug, Pharmacy } from "./pharmacy";
 
 describe("Pharmacy", () => {
+  // General rules
+  it("benefit can't go under 0", () => {
+    expect(new Pharmacy([new Drug("test", -1, 0)]).updateBenefitValue()).toEqual(
+      [new Drug("test", -2, 0)]
+    );
+  });
+
+  it("benefit can't go above 50", () => {
+    expect(new Pharmacy([new Drug("Herbal Tea", 10, 50)]).updateBenefitValue()).toEqual(
+      [new Drug("Herbal Tea", 9, 50)]
+    );
+  });
+
+
+  // General drugs
   it("should decrease the benefit and expiresIn", () => {
     expect(new Pharmacy([new Drug("test", 2, 3)]).updateBenefitValue()).toEqual(
       [new Drug("test", 1, 2)]
     );
   });
+
+  it("benefit degrades twice as fast when expiration date has passed", () => {
+    expect(new Pharmacy([new Drug("test", -1, 38)]).updateBenefitValue()).toEqual(
+      [new Drug("test", -2, 36)]
+    );
+  });
+
+
+  // Herbal Tea
+  it("Herbal Tea benefit increases instead of decreasing", () => {
+    expect(new Pharmacy([new Drug("Herbal Tea", 4, 27)]).updateBenefitValue()).toEqual(
+      [new Drug("Herbal Tea", 3, 28)]
+    );
+  });
+
+  it("Herbal Tea benefit increases twice as fast after the expiration date", () => {
+    expect(new Pharmacy([new Drug("Herbal Tea", 0, 14)]).updateBenefitValue()).toEqual(
+      [new Drug("Herbal Tea", -1, 16)]
+    );
+  });
+
+
+  // Magic Pill
+  it("Magic Pill benefit and expiresIn never change", () => {
+    expect(new Pharmacy([new Drug("Magic Pill", 8, 22)]).updateBenefitValue()).toEqual(
+      [new Drug("Magic Pill", 8, 22)]
+    );
+  });
+
+
+  // Fervex
+  it("Fervex increases in benefit instead of decreasing", () => {
+    expect(new Pharmacy([new Drug("Fervex", 20, 17)]).updateBenefitValue()).toEqual(
+      [new Drug("Fervex", 19, 18)]
+    );
+  });
+
+  it("Fervex increases by 2 when 5 < expiresIn < 10", () => {
+    expect(new Pharmacy([new Drug("Fervex", 8, 17)]).updateBenefitValue()).toEqual(
+      [new Drug("Fervex", 7, 19)]
+    );
+  });
+
+  it("Fervex increases by 3 when 0 <= expiresIn < 6", () => {
+    expect(new Pharmacy([new Drug("Fervex", 4, 17)]).updateBenefitValue()).toEqual(
+      [new Drug("Fervex", 3, 20)]
+    );
+  });
+
+  it("Fervex benefit goes to 0 if expiration date has passed", () => {
+    expect(new Pharmacy([new Drug("Fervex", 0, 17)]).updateBenefitValue()).toEqual(
+      [new Drug("Fervex", -1, 0)]
+    );
+  });
+
+
+  // Dafalgan
+  it("Dafalgan degrades in benefit twice as fast as normal drugs", () => {
+    expect(new Pharmacy([new Drug("Dafalgan", 20, 45)]).updateBenefitValue()).toEqual(
+      [new Drug("Dafalgan", 19, 43)]
+    );
+  });
+
+
+  // Multiple Drugs at once
+  it("multiple drugs all update correctly", () => {
+    const inputDrugs = [
+      new Drug("Doliprane", 20, 41),
+      new Drug("Herbal Tea", -2, 9),
+      new Drug("Fervex", 3, 28),
+      new Drug("Magic Pill", 12, 25),
+      new Drug("Dafalgan", 20, 39)
+    ];
+
+    const outputDrugs = [
+      new Drug("Doliprane", 19, 40),
+      new Drug("Herbal Tea", -3, 11),
+      new Drug("Fervex", 2, 31),
+      new Drug("Magic Pill", 12, 25),
+      new Drug("Dafalgan", 19, 37)
+    ];
+
+    expect(new Pharmacy(inputDrugs).updateBenefitValue()).toEqual(
+      outputDrugs
+    );
+  });
 });
+
+