diff --git a/jest.setup.js b/jest.setup.js
index d583d1a..49b6721 100644
--- a/jest.setup.js
+++ b/jest.setup.js
@@ -1,3 +1,4 @@
 jest.setTimeout(1 * 1000); // 1 second
 jest.resetModules();
-jest.resetAllMocks();
\ No newline at end of file
+jest.resetAllMocks();
+jest.useFakeTimers("modern");
\ No newline at end of file
diff --git a/tests/database/entities/app/UserEffect.test.ts b/tests/database/entities/app/UserEffect.test.ts
index bcd5b21..66992ec 100644
--- a/tests/database/entities/app/UserEffect.test.ts
+++ b/tests/database/entities/app/UserEffect.test.ts
@@ -1,4 +1,3 @@
-import AppDataSource from "../../../../src/database/dataSources/appDataSource";
 import UserEffect from "../../../../src/database/entities/app/UserEffect";
 
 let userEffect: UserEffect;
diff --git a/tests/helpers/EffectHelper.test.ts b/tests/helpers/EffectHelper.test.ts
index 9e3b5b0..21bb3e6 100644
--- a/tests/helpers/EffectHelper.test.ts
+++ b/tests/helpers/EffectHelper.test.ts
@@ -31,23 +31,86 @@ describe("AddEffectToUserInventory", () => {
     });
 
     describe("GIVEN effect is not in database", () => {
-        test.todo("EXPECT effect to be created");
+        beforeAll(async () => {
+            UserEffect.FetchOneByUserIdAndName = jest.fn().mockResolvedValue(null);
+            UserEffect.prototype.Save = jest.fn();
 
-        test.todo("EXPECT effect to be saved");
+            await EffectHelper.AddEffectToUserInventory("userId", "name", 1);
+        });
+
+        test("EXPECT effect to be saved", () => {
+            expect(UserEffect.prototype.Save).toHaveBeenCalledTimes(1);
+            expect(UserEffect.prototype.Save).toHaveBeenCalledWith(UserEffect, expect.any(UserEffect));
+        });
     });
 });
 
 describe("UseEffect", () => {
     describe("GIVEN effect is in database", () => {
-        describe("GIVEN effect.WhenExpires is undefined", () => {
-            test.todo("EXPECT false returned");
-        });
-
         describe("GIVEN now is before effect.WhenExpires", () => {
-            test.todo("EXPECT false returned");
+            let result: boolean | undefined;
+
+            // nowMock < whenExpires
+            const nowMock = new Date(2024, 11, 3, 13, 30);
+            const whenExpires = new Date(2024, 11, 3, 14, 0);
+
+            const userEffect = {
+                Unused: 1,
+                WhenExpires: whenExpires,
+            };
+            
+            beforeAll(async () => {
+                jest.setSystemTime(nowMock);
+
+                UserEffect.FetchOneByUserIdAndName = jest.fn().mockResolvedValue(userEffect);
+
+                result = await EffectHelper.UseEffect("userId", "name", new Date());
+            });
+
+            test("EXPECT false returned", () => {
+                expect(result).toBe(false);
+            });
         });
 
         describe("GIVEN currently used effect is inactive", () => {
+            let result: boolean | undefined;
+
+            // nowMock > whenExpires
+            const nowMock = new Date(2024, 11, 3, 13, 30);
+            const whenExpires = new Date(2024, 11, 3, 13, 0);
+            const whenExpiresNew = new Date(2024, 11, 3, 15, 0);
+
+            const userEffect = {
+                Unused: 1,
+                WhenExpires: whenExpires,
+                UseEffect: jest.fn(),
+                Save: jest.fn(),
+            };
+            
+            beforeAll(async () => {
+                jest.setSystemTime(nowMock);
+
+                UserEffect.FetchOneByUserIdAndName = jest.fn().mockResolvedValue(userEffect);
+
+                result = await EffectHelper.UseEffect("userId", "name", whenExpiresNew);
+            });
+
+            test("EXPECT UseEffect to be called", () => {
+                expect(userEffect.UseEffect).toHaveReturnedTimes(1);
+                expect(userEffect.UseEffect).toHaveBeenCalledWith(whenExpiresNew);
+            });
+
+            test("EXPECT effect to be saved", () => {
+                expect(userEffect.Save).toHaveBeenCalledTimes(1);
+                expect(userEffect.Save).toHaveBeenCalledWith(UserEffect, userEffect);
+            });
+
+            test("EXPECT true returned", () => {
+                expect(result).toBe(true);
+            });
+        });
+
+        describe("GIVEN effect.WhenExpires is null", () => {
             test.todo("EXPECT UseEffect to be called");
 
             test.todo("EXPECT effect to be saved");