diff --git a/src/01-simple-tests/index.test.ts b/src/01-simple-tests/index.test.ts
index fbbea85de..2b6601da1 100644
--- a/src/01-simple-tests/index.test.ts
+++ b/src/01-simple-tests/index.test.ts
@@ -1,32 +1,49 @@
-// Uncomment the code below and write your tests
-// import { simpleCalculator, Action } from './index';
+import { simpleCalculator, Action } from './index';
 
 describe('simpleCalculator tests', () => {
   test('should add two numbers', () => {
-    // Write your test here
+    const input = { a: 3, b: 5, action: Action.Add };
+    const result = simpleCalculator(input);
+    expect(result).toBe(8);
   });
 
   test('should subtract two numbers', () => {
-    // Write your test here
+    const input = { a: 10, b: 4, action: Action.Subtract };
+    const result = simpleCalculator(input);
+    expect(result).toBe(6);
   });
 
   test('should multiply two numbers', () => {
-    // Write your test here
+    const input = { a: 6, b: 7, action: Action.Multiply };
+    const result = simpleCalculator(input);
+    expect(result).toBe(42);
   });
 
   test('should divide two numbers', () => {
-    // Write your test here
+    const input = { a: 20, b: 5, action: Action.Divide };
+    const result = simpleCalculator(input);
+    expect(result).toBe(4);
   });
 
   test('should exponentiate two numbers', () => {
-    // Write your test here
+    const input = { a: 2, b: 3, action: Action.Exponentiate };
+    const result = simpleCalculator(input);
+    expect(result).toBe(8);
   });
 
   test('should return null for invalid action', () => {
-    // Write your test here
+    const input = { a: 5, b: 10, action: 'invalid_action' };
+    const result = simpleCalculator(input);
+    expect(result).toBeNull();
   });
 
   test('should return null for invalid arguments', () => {
-    // Write your test here
+    const input1 = { a: 'string', b: 10, action: Action.Add };
+    const input2 = { a: 5, b: null, action: Action.Subtract };
+    const input3 = { a: 5, b: 10, action: 123 }; // invalid action type
+
+    expect(simpleCalculator(input1)).toBeNull();
+    expect(simpleCalculator(input2)).toBeNull();
+    expect(simpleCalculator(input3)).toBeNull();
   });
 });
diff --git a/src/02-table-tests/index.test.ts b/src/02-table-tests/index.test.ts
index 4f36e892e..f150f95e3 100644
--- a/src/02-table-tests/index.test.ts
+++ b/src/02-table-tests/index.test.ts
@@ -1,17 +1,35 @@
-// Uncomment the code below and write your tests
-/* import {  simpleCalculator, Action } from './index';
+import { simpleCalculator, Action } from './index';
 
 const testCases = [
-    { a: 1, b: 2, action: Action.Add, expected: 3 },
-    { a: 2, b: 2, action: Action.Add, expected: 4 },
-    { a: 3, b: 2, action: Action.Add, expected: 5 },
-    // continue cases for other actions    
-]; */
+  { a: 1, b: 2, action: Action.Add, expected: 3 },
+  { a: 2, b: 2, action: Action.Add, expected: 4 },
+  { a: 3, b: 2, action: Action.Add, expected: 5 },
+  { a: 5, b: 3, action: Action.Subtract, expected: 2 },
+  { a: 6, b: 2, action: Action.Subtract, expected: 4 },
+  { a: 3, b: 3, action: Action.Multiply, expected: 9 },
+  { a: 8, b: 2, action: Action.Multiply, expected: 16 },
+  { a: 10, b: 2, action: Action.Divide, expected: 5 },
+  { a: 9, b: 3, action: Action.Divide, expected: 3 },
+  { a: 2, b: 3, action: Action.Exponentiate, expected: 8 },
+  { a: 5, b: 2, action: Action.Exponentiate, expected: 25 },
+];
 
 describe('simpleCalculator', () => {
-  // This test case is just to run this test suite, remove it when you write your own tests
-  test('should blah-blah', () => {
-    expect(true).toBe(true);
+  test.each(testCases)(
+    'should calculate $a $action $b to be $expected',
+    ({ a, b, action, expected }) => {
+      const result = simpleCalculator({ a, b, action });
+      expect(result).toBe(expected);
+    },
+  );
+
+  test('should return null for invalid action', () => {
+    const result = simpleCalculator({ a: 1, b: 2, action: 'invalid' });
+    expect(result).toBeNull();
+  });
+
+  test('should return null for invalid arguments', () => {
+    const result = simpleCalculator({ a: '1', b: 2, action: Action.Add });
+    expect(result).toBeNull();
   });
-  // Consider to use Jest table tests API to test all cases above
-});
+});
\ No newline at end of file
diff --git a/src/03-error-handling-async/index.test.ts b/src/03-error-handling-async/index.test.ts
index 6e106a6d6..b5a3a55d1 100644
--- a/src/03-error-handling-async/index.test.ts
+++ b/src/03-error-handling-async/index.test.ts
@@ -1,30 +1,44 @@
-// Uncomment the code below and write your tests
-// import { throwError, throwCustomError, resolveValue, MyAwesomeError, rejectCustomError } from './index';
+import {
+  throwError,
+  throwCustomError,
+  resolveValue,
+  MyAwesomeError,
+  rejectCustomError,
+} from './index';
 
 describe('resolveValue', () => {
   test('should resolve provided value', async () => {
-    // Write your test here
+    const value = 'test';
+    const result = await resolveValue(value);
+    expect(result).toBe(value);
   });
 });
 
 describe('throwError', () => {
   test('should throw error with provided message', () => {
-    // Write your test here
+    const errorMessage = 'Custom error message';
+    expect(() => throwError(errorMessage)).toThrowError(errorMessage);
   });
 
   test('should throw error with default message if message is not provided', () => {
-    // Write your test here
+    expect(() => throwError()).toThrowError('Oops!');
   });
 });
 
 describe('throwCustomError', () => {
   test('should throw custom error', () => {
-    // Write your test here
+    expect(() => throwCustomError()).toThrowError(MyAwesomeError);
+    expect(() => throwCustomError()).toThrowError(
+      'This is my awesome custom error!',
+    );
   });
 });
 
 describe('rejectCustomError', () => {
   test('should reject custom error', async () => {
-    // Write your test here
+    await expect(rejectCustomError()).rejects.toThrowError(MyAwesomeError);
+    await expect(rejectCustomError()).rejects.toThrowError(
+      'This is my awesome custom error!',
+    );
   });
 });
diff --git a/src/04-test-class/index.test.ts b/src/04-test-class/index.test.ts
index 937490d82..c991654a2 100644
--- a/src/04-test-class/index.test.ts
+++ b/src/04-test-class/index.test.ts
@@ -1,44 +1,84 @@
-// Uncomment the code below and write your tests
-// import { getBankAccount } from '.';
+import {
+  getBankAccount,
+  InsufficientFundsError,
+  TransferFailedError,
+  SynchronizationFailedError,
+} from './index';
+import { random } from 'lodash';
+
+jest.mock('lodash', () => ({
+  random: jest.fn(),
+}));
 
 describe('BankAccount', () => {
   test('should create account with initial balance', () => {
-    // Write your test here
+    const account = getBankAccount(100);
+    expect(account.getBalance()).toBe(100);
   });
 
   test('should throw InsufficientFundsError error when withdrawing more than balance', () => {
-    // Write your test here
+    const account = getBankAccount(50);
+    expect(() => account.withdraw(100)).toThrow(InsufficientFundsError);
+    expect(() => account.withdraw(100)).toThrow(
+      'Insufficient funds: cannot withdraw more than 50',
+    );
   });
 
   test('should throw error when transferring more than balance', () => {
-    // Write your test here
+    const account1 = getBankAccount(50);
+    const account2 = getBankAccount(100);
+
+    expect(() => account1.transfer(100, account2)).toThrow(
+      InsufficientFundsError,
+    );
   });
 
   test('should throw error when transferring to the same account', () => {
-    // Write your test here
+    const account = getBankAccount(50);
+    expect(() => account.transfer(10, account)).toThrow(TransferFailedError);
+    expect(() => account.transfer(10, account)).toThrow('Transfer failed');
   });
 
   test('should deposit money', () => {
-    // Write your test here
+    const account = getBankAccount(50);
+    account.deposit(50);
+    expect(account.getBalance()).toBe(100);
   });
 
   test('should withdraw money', () => {
-    // Write your test here
+    const account = getBankAccount(100);
+    account.withdraw(50);
+    expect(account.getBalance()).toBe(50);
   });
 
   test('should transfer money', () => {
-    // Write your test here
+    const account1 = getBankAccount(100);
+    const account2 = getBankAccount(50);
+
+    account1.transfer(50, account2);
+    expect(account1.getBalance()).toBe(50);
+    expect(account2.getBalance()).toBe(100);
   });
 
-  test('fetchBalance should return number in case if request did not failed', async () => {
-    // Write your tests here
+  test('fetchBalance should return number in case request did not fail', async () => {
+    (random as jest.Mock).mockReturnValueOnce(75).mockReturnValueOnce(1);
+    const account = getBankAccount(100);
+    const balance = await account.fetchBalance();
+    expect(balance).toBe(75);
   });
 
   test('should set new balance if fetchBalance returned number', async () => {
-    // Write your tests here
+    (random as jest.Mock).mockReturnValueOnce(75).mockReturnValueOnce(1);
+    const account = getBankAccount(100);
+    await account.synchronizeBalance();
+    expect(account.getBalance()).toBe(75);
   });
 
   test('should throw SynchronizationFailedError if fetchBalance returned null', async () => {
-    // Write your tests here
+    (random as jest.Mock).mockReturnValueOnce(50).mockReturnValueOnce(0);
+    const account = getBankAccount(100);
+    await expect(account.synchronizeBalance()).rejects.toThrow(
+      SynchronizationFailedError,
+    );
   });
 });
diff --git a/src/05-partial-mocking/index.test.ts b/src/05-partial-mocking/index.test.ts
index 9d8a66cbd..6fe2aaa12 100644
--- a/src/05-partial-mocking/index.test.ts
+++ b/src/05-partial-mocking/index.test.ts
@@ -1,8 +1,12 @@
-// Uncomment the code below and write your tests
-// import { mockOne, mockTwo, mockThree, unmockedFunction } from './index';
+import { mockOne, mockTwo, mockThree, unmockedFunction } from './index';
 
 jest.mock('./index', () => {
-  // const originalModule = jest.requireActual<typeof import('./index')>('./index');
+  return {
+    mockOne: jest.fn(),
+    mockTwo: jest.fn(),
+    mockThree: jest.fn(),
+    unmockedFunction: jest.requireActual('./index').unmockedFunction,
+  };
 });
 
 describe('partial mocking', () => {
@@ -11,10 +15,23 @@ describe('partial mocking', () => {
   });
 
   test('mockOne, mockTwo, mockThree should not log into console', () => {
-    // Write your test here
+    const consoleSpy = jest.spyOn(console, 'log');
+
+    mockOne();
+    mockTwo();
+    mockThree();
+
+    expect(consoleSpy).not.toHaveBeenCalledWith('foo');
+    expect(consoleSpy).not.toHaveBeenCalledWith('bar');
+    expect(consoleSpy).not.toHaveBeenCalledWith('baz');
+
+    consoleSpy.mockRestore();
   });
 
   test('unmockedFunction should log into console', () => {
-    // Write your test here
+    const consoleSpy = jest.spyOn(console, 'log');
+    unmockedFunction();
+    expect(consoleSpy).toHaveBeenCalledWith('I am not mocked');
+    consoleSpy.mockRestore();
   });
 });
diff --git a/src/06-mocking-node-api/index.test.ts b/src/06-mocking-node-api/index.test.ts
index 8dc3afd79..f1d43c824 100644
--- a/src/06-mocking-node-api/index.test.ts
+++ b/src/06-mocking-node-api/index.test.ts
@@ -1,5 +1,19 @@
-// Uncomment the code below and write your tests
-// import { readFileAsynchronously, doStuffByTimeout, doStuffByInterval } from '.';
+import { readFileAsynchronously, doStuffByTimeout, doStuffByInterval } from '.';
+import { existsSync } from 'fs';
+import { readFile } from 'fs/promises';
+import { join } from 'path';
+
+jest.mock('fs', () => ({
+  existsSync: jest.fn(),
+}));
+
+jest.mock('fs/promises', () => ({
+  readFile: jest.fn(),
+}));
+
+jest.mock('path', () => ({
+  join: jest.fn(),
+}));
 
 describe('doStuffByTimeout', () => {
   beforeAll(() => {
@@ -11,11 +25,19 @@ describe('doStuffByTimeout', () => {
   });
 
   test('should set timeout with provided callback and timeout', () => {
-    // Write your test here
+    const callback = jest.fn();
+    const timeout = 1000;
+    jest.spyOn(global, 'setTimeout');
+    doStuffByTimeout(callback, timeout);
+    expect(setTimeout).toHaveBeenCalledWith(callback, timeout);
   });
 
   test('should call callback only after timeout', () => {
-    // Write your test here
+    const callback = jest.fn();
+    const timeout = 1000;
+    doStuffByTimeout(callback, timeout);
+    jest.advanceTimersByTime(timeout);
+    expect(callback).toHaveBeenCalled();
   });
 });
 
@@ -29,24 +51,58 @@ describe('doStuffByInterval', () => {
   });
 
   test('should set interval with provided callback and timeout', () => {
-    // Write your test here
+    const callback = jest.fn();
+    const interval = 1000;
+    jest.spyOn(global, 'setInterval');
+    doStuffByInterval(callback, interval);
+    expect(setInterval).toHaveBeenCalledWith(callback, interval);
   });
 
   test('should call callback multiple times after multiple intervals', () => {
-    // Write your test here
+    const callback = jest.fn();
+    const interval = 1000;
+
+    doStuffByInterval(callback, interval);
+    jest.advanceTimersByTime(interval * 3);
+    expect(callback).toHaveBeenCalledTimes(3);
   });
 });
 
 describe('readFileAsynchronously', () => {
+  const mockFullPath = './test.txt';
+
+  beforeEach(() => {
+    (join as jest.Mock).mockReturnValue(mockFullPath);
+  });
+
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
   test('should call join with pathToFile', async () => {
-    // Write your test here
+    const pathToFile = 'test.txt';
+
+    await readFileAsynchronously(pathToFile);
+
+    expect(join).toHaveBeenCalledWith(__dirname, pathToFile);
   });
 
   test('should return null if file does not exist', async () => {
-    // Write your test here
+    (existsSync as jest.Mock).mockReturnValue(false);
+
+    const result = await readFileAsynchronously('test.txt');
+
+    expect(result).toBeNull();
+    expect(readFile).not.toHaveBeenCalled();
   });
 
   test('should return file content if file exists', async () => {
-    // Write your test here
+    (existsSync as jest.Mock).mockReturnValue(true);
+    (readFile as jest.Mock).mockResolvedValue(Buffer.from('file content'));
+
+    const result = await readFileAsynchronously('test.txt');
+
+    expect(result).toBe('file content');
+    expect(readFile).toHaveBeenCalledWith(mockFullPath);
   });
 });
diff --git a/src/07-mocking-lib-api/index.test.ts b/src/07-mocking-lib-api/index.test.ts
index e1dd001ef..78e6a897a 100644
--- a/src/07-mocking-lib-api/index.test.ts
+++ b/src/07-mocking-lib-api/index.test.ts
@@ -1,17 +1,60 @@
-// Uncomment the code below and write your tests
-/* import axios from 'axios';
-import { throttledGetDataFromApi } from './index'; */
+import axios from 'axios';
+import { throttledGetDataFromApi } from './index';
+
+jest.mock('axios');
+jest.mock('lodash', () => ({
+  throttle: jest.fn((fn) => fn), // Mock throttle to bypass throttling behavior for tests
+}));
 
 describe('throttledGetDataFromApi', () => {
-  test('should create instance with provided base url', async () => {
-    // Write your test here
+  beforeEach(() => {
+    jest.clearAllMocks(); // Clear any previously stored mocks
+  });
+
+  test('should create instance with provided base URL', async () => {
+    const relativePath = '/posts/1';
+    const mockResponse = { data: { id: 1, title: 'Test Post' } };
+
+    // Mock the axios.create() and axios.get() behavior
+    const axiosInstance = { get: jest.fn().mockResolvedValue(mockResponse) };
+    (axios.create as jest.Mock).mockReturnValue(axiosInstance);
+
+    // Call the function
+    await throttledGetDataFromApi(relativePath);
+
+    // Check that axios.create was called with the correct base URL
+    expect(axios.create).toHaveBeenCalledWith({
+      baseURL: 'https://jsonplaceholder.typicode.com',
+    });
   });
 
-  test('should perform request to correct provided url', async () => {
-    // Write your test here
+  test('should perform request to correct provided URL', async () => {
+    const relativePath = '/posts/1';
+    const mockResponse = { data: { id: 1, title: 'Test Post' } };
+
+    // Mock the axios.create() and axios.get() behavior
+    const axiosInstance = { get: jest.fn().mockResolvedValue(mockResponse) };
+    (axios.create as jest.Mock).mockReturnValue(axiosInstance);
+
+    // Call the function
+    await throttledGetDataFromApi(relativePath);
+
+    // Check that axios.get was called with the correct relative URL
+    expect(axiosInstance.get).toHaveBeenCalledWith(relativePath);
   });
 
   test('should return response data', async () => {
-    // Write your test here
+    const relativePath = '/posts/1';
+    const mockResponse = { data: { id: 1, title: 'Test Post' } };
+
+    // Mock the axios.create() and axios.get() behavior
+    const axiosInstance = { get: jest.fn().mockResolvedValue(mockResponse) };
+    (axios.create as jest.Mock).mockReturnValue(axiosInstance);
+
+    // Call the function and capture the result
+    const result = await throttledGetDataFromApi(relativePath);
+
+    // Check that the returned data matches the mock response data
+    expect(result).toEqual(mockResponse.data);
   });
 });
diff --git a/src/08-snapshot-testing/__snapshots__/index.test.ts.snap b/src/08-snapshot-testing/__snapshots__/index.test.ts.snap
new file mode 100644
index 000000000..b2b79dc2e
--- /dev/null
+++ b/src/08-snapshot-testing/__snapshots__/index.test.ts.snap
@@ -0,0 +1,20 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`generateLinkedList should generate linked list from values 2 1`] = `
+{
+  "next": {
+    "next": {
+      "next": {
+        "next": {
+          "next": null,
+          "value": null,
+        },
+        "value": 7,
+      },
+      "value": 6,
+    },
+    "value": 5,
+  },
+  "value": 4,
+}
+`;
diff --git a/src/08-snapshot-testing/index.test.ts b/src/08-snapshot-testing/index.test.ts
index 67c345706..7029cfcb8 100644
--- a/src/08-snapshot-testing/index.test.ts
+++ b/src/08-snapshot-testing/index.test.ts
@@ -1,14 +1,31 @@
-// Uncomment the code below and write your tests
-// import { generateLinkedList } from './index';
+import { generateLinkedList } from './index';
 
 describe('generateLinkedList', () => {
-  // Check match by expect(...).toStrictEqual(...)
   test('should generate linked list from values 1', () => {
-    // Write your test here
+    const elements = [1, 2, 3];
+
+    const expectedList = {
+      value: 1,
+      next: {
+        value: 2,
+        next: {
+          value: 3,
+          next: {
+            value: null,
+            next: null,
+          },
+        },
+      },
+    };
+
+    const result = generateLinkedList(elements);
+    expect(result).toStrictEqual(expectedList);
   });
 
-  // Check match by comparison with snapshot
   test('should generate linked list from values 2', () => {
-    // Write your test here
+    const elements = [4, 5, 6, 7];
+
+    const result = generateLinkedList(elements);
+    expect(result).toMatchSnapshot();
   });
 });