IDE and Extensions for Testers: Complete Tooling Guide for QA Engineers

Modern software testing requires more than just manual clicking and exploratory testing. Today’s QA engineers need powerful development environments, specialized extensions, and debugging tools to write automated tests, analyze network traffic, and investigate bugs efficiently. This comprehensive guide covers the essential IDEs, extensions, and tools that every tester should master.

VS Code for QA Engineers

Visual Studio Code has become the go-to editor for many testers due to its lightweight nature, extensive extension marketplace, and excellent support for multiple programming languages. Let’s explore how to transform VS Code into a powerful testing environment.

Essential Extensions for Testers

1. Test Runner Extensions

Jest Runner

Direct integration with Jest testing framework
Run individual tests or test suites with one click
Display test results inline in the editor
Debug tests directly from the editor

Installation:

code --install-extension Orta.vscode-jest

Configuration in .vscode/settings.json:

{
  "jest.autoRun": "off",
  "jest (as discussed in [From Manual to Automation: Complete Transition Guide for QA Engineers](/blog/manual-to-automation-transition)).showCoverageOnLoad": true,
  "jest.coverageFormatter": "DefaultFormatter",
  "jest.debugMode": true
}

Test Explorer UI

Unified test explorer for multiple frameworks
Supports Jest, Mocha, Pytest, JUnit, and more
Tree view of all tests with pass/fail indicators
Quick navigation to test definitions

code --install-extension hbenl.vscode-test-explorer

Playwright Test for VSCode

Run Playwright tests directly from VS Code
Pick locators with visual selector tool
Record tests with codegen integration
Debug with breakpoints

code --install-extension ms-playwright.playwright

Configuration example:

{
  "playwright.reuseBrowser": true,
  "playwright (as discussed in [Cloud Testing Platforms: Complete Guide to BrowserStack, Sauce Labs, AWS Device Farm & More](/blog/cloud-testing-platforms)).showTrace": true,
  "playwright.env": {
    "HEADLESS": "false"
  }
}

2. Code Quality and Linting

ESLint Essential for JavaScript/TypeScript test code quality:

code --install-extension dbaeumer.vscode-eslint

.eslintrc.js for test files:

module.exports = {
  env: {
    node: true,
    jest: true,
    mocha: true
  },
  extends: [
    'eslint:recommended',
    'plugin:jest/recommended'
  ],
  rules: {
    'jest/no-disabled-tests': 'warn',
    'jest/no-focused-tests': 'error',
    'jest/valid-expect': 'error'
  }
}

Prettier Consistent code formatting for test automation:

code --install-extension esbenp.prettier-vscode

Configuration:

{
  "editor.formatOnSave": true,
  "prettier.singleQuote": true,
  "prettier.semi": false,
  "prettier.tabWidth": 2
}

3. API Testing Extensions

REST Client Test API endpoints without leaving VS Code:

code --install-extension humao.rest-client

Create .http files for API testing:

### Get User by ID
GET https://api.example.com/users/123
Authorization: Bearer {{token}}

### Create New User
POST https://api.example.com/users
Content-Type: application/json

{
  "name": "John Doe",
  "email": "john@example.com"
}

### Variables
@baseUrl = https://api.example.com
@token = eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...

### Using Variables
GET {{baseUrl}}/profile
Authorization: Bearer {{token}}

Thunder Client Lightweight alternative to Postman:

code --install-extension rangav.vscode-thunder-client

Features:

Collections and environments
Graphical interface for API testing
Generate code snippets in multiple languages
Import/export Postman collections

4. Debugging and Inspection

JavaScript Debugger Built into VS Code, but requires configuration:

Create .vscode/launch.json:

{
  "version": "0.2.0",
  "configurations": [
    {
      "type": "node",
      "request": "launch",
      "name": "Jest Current File",
      "program": "${workspaceFolder}/node_modules/.bin/jest",
      "args": [
        "${fileBasename}",
        "--runInBand",
        "--no-cache"
      ],
      "console": "integratedTerminal",
      "internalConsoleOptions": "neverOpen"
    },
    {
      "type": "node",
      "request": "launch",
      "name": "Debug Playwright Test",
      "program": "${workspaceFolder}/node_modules/.bin/playwright",
      "args": [
        "test",
        "${file}",
        "--debug"
      ],
      "console": "integratedTerminal"
    }
  ]
}

CodeLLDB (for Python testing):

code --install-extension vadimcn.vscode-lldb

Python debugging configuration:

{
  "type": "python",
  "request": "launch",
  "name": "Pytest Current File",
  "module": "pytest",
  "args": [
    "${file}",
    "-v",
    "-s"
  ],
  "console": "integratedTerminal"
}

5. Version Control and Collaboration

GitLens Enhanced Git capabilities for tracking test changes:

code --install-extension eamodio.gitlens

Key features for testers:

Blame annotations showing who wrote each test
File history to track test evolution
Compare test versions across branches
Line history for understanding test modifications

Live Share Pair testing and collaborative debugging:

code --install-extension MS-vsliveshare.vsliveshare

Use cases:

Pair programming on test automation
Remote debugging sessions
Collaborative test review
Knowledge sharing sessions

Custom Snippets for Test Automation

Create custom snippets in Code > Preferences > User Snippets:

Jest Test Snippets (javascript.json):

{
  "Jest Describe Block": {
    "prefix": "desc",
    "body": [
      "describe('${1:suite name}', () => {",
      "  ${2:// test code}",
      "});"
    ]
  },
  "Jest Test Case": {
    "prefix": "test",
    "body": [
      "test('${1:test name}', async () => {",
      "  ${2:// test implementation}",
      "});"
    ]
  },
  "Jest Before Each": {
    "prefix": "beforeach",
    "body": [
      "beforeEach(async () => {",
      "  ${1:// setup code}",
      "});"
    ]
  },
  "API Test Template": {
    "prefix": "apitest",
    "body": [
      "test('${1:endpoint} should ${2:expected behavior}', async () => {",
      "  const response = await request(app)",
      "    .${3:get}('${4:/api/endpoint}')",
      "    .set('Authorization', `Bearer \\${token}`);",
      "",
      "  expect(response.status).toBe(${5:200});",
      "  expect(response.body).toMatchObject({",
      "    ${6:// expected properties}",
      "  });",
      "});"
    ]
  }
}

Playwright Snippets:

{
  "Playwright Test": {
    "prefix": "pwtest",
    "body": [
      "test('${1:test description}', async ({ page }) => {",
      "  await page.goto('${2:https://example.com}');",
      "  ${3:// test steps}",
      "});"
    ]
  },
  "Playwright Expect": {
    "prefix": "pwexpect",
    "body": [
      "await expect(page.locator('${1:selector}')).${2:toBeVisible}();"
    ]
  }
}

Workspace Configuration for Test Projects

Create .vscode/settings.json for your test project:

{
  "files.exclude": {
    "**/.git": true,
    "**/node_modules": true,
    "**/coverage": true,
    "**/playwright-report": true
  },
  "search.exclude": {
    "**/node_modules": true,
    "**/coverage": true,
    "**/dist": true
  },
  "editor.codeActionsOnSave": {
    "source.fixAll.eslint": true
  },
  "files.associations": {
    "*.spec.js": "javascript",
    "*.test.js": "javascript",
    "*.http": "http"
  },
  "jest.autoRun": {
    "watch": false,
    "onSave": "test-file"
  },
  "testing.automaticallyOpenPeekView": "failureInVisibleDocument",
  "terminal.integrated.defaultProfile.osx": "zsh",
  "npm.enableScriptExplorer": true
}

Tasks for Common Testing Operations

Create .vscode/tasks.json:

{
  "version": "2.0.0",
  "tasks": [
    {
      "label": "Run All Tests",
      "type": "npm",
      "script": "test",
      "problemMatcher": [],
      "presentation": {
        "reveal": "always",
        "panel": "new"
      }
    },
    {
      "label": "Run Tests with Coverage",
      "type": "npm",
      "script": "test:coverage",
      "problemMatcher": [],
      "presentation": {
        "reveal": "always"
      }
    },
    {
      "label": "Lint Test Files",
      "type": "npm",
      "script": "lint",
      "problemMatcher": ["$eslint-stylish"]
    },
    {
      "label": "Generate Playwright Report",
      "type": "shell",
      "command": "npx playwright show-report",
      "problemMatcher": []
    }
  ]
}

Keyboard Shortcuts for Productivity

Customize keyboard shortcuts in Keybindings (JSON):

[
  {
    "key": "ctrl+shift+t",
    "command": "testing.runCurrentFile"
  },
  {
    "key": "ctrl+shift+d",
    "command": "testing.debugCurrentFile"
  },
  {
    "key": "ctrl+shift+a",
    "command": "testing.runAll"
  },
  {
    "key": "ctrl+shift+f",
    "command": "testing.reRunFailTests"
  }
]

Multi-Root Workspaces for Complex Projects

For projects with separate frontend and backend tests:

Create test-automation.code-workspace:

{
  "folders": [
    {
      "name": "API Tests",
      "path": "./api-tests"
    },
    {
      "name": "E2E Tests",
      "path": "./e2e-tests"
    },
    {
      "name": "Performance Tests",
      "path": "./performance-tests"
    }
  ],
  "settings": {
    "files.watcherExclude": {
      "**/node_modules/**": true
    }
  }
}

IntelliJ IDEA for Testing

IntelliJ IDEA (and other JetBrains IDEs) provide powerful features for Java-based test automation, including excellent support for JUnit, TestNG, Selenium, and other testing frameworks.

Essential Plugins for Testing

1. Test Automation Plugins

JUnit 5 Support (Built-in)

Run tests from editor gutter icons
Navigate between tests and production code
Generate test methods automatically
Coverage analysis

Configuration in Run Configuration:

VM options: -ea -Dfile.encoding=UTF-8
Working directory: $MODULE_WORKING_DIR$
Environment variables: ENV=test

TestNG Plugin Advanced testing framework support:

<!-- pom.xml dependency -->
<dependency>
    <groupId>org.testng</groupId>
    <artifactId>testng</artifactId>
    <version>7.8.0</version>
    <scope>test</scope>
</dependency>

TestNG configuration (testng.xml):

<!DOCTYPE suite SYSTEM "https://testng.org/testng-1.0.dtd">
<suite name="Test Suite" parallel="methods" thread-count="5">
    <test name="API Tests">
        <classes>
            <class name="com.example.tests.UserApiTest"/>
            <class name="com.example.tests.ProductApiTest"/>
        </classes>
    </test>
    <test name="UI Tests">
        <packages>
            <package name="com.example.tests.ui"/>
        </packages>
    </test>
</suite>

Cucumber for Java BDD testing support:

Settings > Plugins > Install "Cucumber for Java"

Features:

Gherkin syntax highlighting
Navigation from steps to step definitions
Generate step definitions from feature files
Run scenarios from editor

Example feature file:

Feature: User Authentication

  Background:
    Given the application is running
    And the database is clean

  @smoke @api
  Scenario: Successful login with valid credentials
    Given a user with username "testuser" exists
    When the user logs in with username "testuser" and password "Test123!"
    Then the login should be successful
    And a valid JWT token should be returned

  @negative
  Scenario Outline: Failed login attempts
    When the user logs in with username "<username>" and password "<password>"
    Then the login should fail
    And the error message should be "<error>"

    Examples:
      | username  | password  | error                   |
      | invalid   | Test123!  | Invalid credentials     |
      | testuser  | wrong     | Invalid credentials     |
      |           | Test123!  | Username required       |

2. Code Coverage Tools

IntelliJ IDEA Code Coverage (Built-in) Run tests with coverage:

Right-click on test class/package
Select “Run with Coverage”
View coverage in editor gutter and Coverage tool window

Configuration in .idea/workspace.xml:

<component name="CoverageOptionsProvider">
  <option name="myAddOrReplace" value="2" />
  <option name="myGlobalRunner" value="IDEA" />
  <option name="myTraceTestFramework" value="false" />
</component>

JaCoCo Plugin More advanced coverage reporting:

<!-- Maven plugin -->
<plugin>
    <groupId>org.jacoco</groupId>
    <artifactId>jacoco-maven-plugin</artifactId>
    <version>0.8.11</version>
    <executions>
        <execution>
            <goals>
                <goal>prepare-agent</goal>
            </goals>
        </execution>
        <execution>
            <id>report</id>
            <phase>test</phase>
            <goals>
                <goal>report</goal>
            </goals>
        </execution>
        <execution>
            <id>jacoco-check</id>
            <goals>
                <goal>check</goal>
            </goals>
            <configuration>
                <rules>
                    <rule>
                        <element>PACKAGE</element>
                        <limits>
                            <limit>
                                <counter>LINE</counter>
                                <value>COVEREDRATIO</value>
                                <minimum>0.80</minimum>
                            </limit>
                        </limits>
                    </rule>
                </rules>
            </configuration>
        </execution>
    </executions>
</plugin>

3. REST API Testing

HTTP Client (Built-in) Create .http files for API testing:

### Development environment
@host = http://localhost:8080
@token = {{auth_token}}

### Get Authentication Token
# @name auth
POST {{host}}/api/auth/login
Content-Type: application/json

{
  "username": "admin",
  "password": "admin123"
}

> {% client.global.set("auth_token", response.body.token); %}

### Get All Users (Authenticated)
GET {{host}}/api/users
Authorization: Bearer {{token}}

### Create New User
POST {{host}}/api/users
Content-Type: application/json
Authorization: Bearer {{token}}

{
  "username": "newuser",
  "email": "newuser@example.com",
  "role": "USER"
}

### Update User
# @name updateUser
PUT {{host}}/api/users/{{userId}}
Content-Type: application/json
Authorization: Bearer {{token}}

{
  "email": "updated@example.com"
}

### Response handler
> {%
    client.test("Request executed successfully", function() {
        client.assert(response.status === 200, "Response status is not 200");
    });

    client.test("User updated correctly", function() {
        client.assert(response.body.email === "updated@example.com");
    });
%}

### Delete User
DELETE {{host}}/api/users/{{userId}}
Authorization: Bearer {{token}}

4. Database Tools Integration

Database Tools and SQL (Built-in) Connect to test databases for data verification:

Open Database tool window
Add data source (PostgreSQL, MySQL, etc.)
Create SQL console for test data management

Example test data setup script:

-- Setup test data
TRUNCATE TABLE users CASCADE;
TRUNCATE TABLE orders CASCADE;

INSERT INTO users (id, username, email, role, created_at)
VALUES
    (1, 'testuser1', 'test1@example.com', 'USER', NOW()),
    (2, 'testuser2', 'test2@example.com', 'USER', NOW()),
    (3, 'admin', 'admin@example.com', 'ADMIN', NOW());

INSERT INTO orders (id, user_id, product_id, quantity, total, status)
VALUES
    (1, 1, 101, 2, 199.98, 'COMPLETED'),
    (2, 1, 102, 1, 49.99, 'PENDING'),
    (3, 2, 101, 1, 99.99, 'COMPLETED');

-- Verify data
SELECT u.username, COUNT(o.id) as order_count, SUM(o.total) as total_spent
FROM users u
LEFT JOIN orders o ON u.id = o.user_id
GROUP BY u.id, u.username;

Live Templates for Test Code

Create custom live templates in Settings > Editor > Live Templates:

JUnit 5 Test Method:

@Test
@DisplayName("$DESCRIPTION$")
void $METHOD_NAME$() {
    // Arrange
    $ARRANGE$
    
    // Act
    $ACT$
    
    // Assert
    $ASSERT$
}

REST Assured API Test:

@Test
void test$METHOD$Returns$STATUS$() {
    given()
        .contentType(ContentType.JSON)
        .header("Authorization", "Bearer " + token)
        .when()
        .$HTTP_METHOD$("$ENDPOINT$")
        .then()
        .statusCode($STATUS_CODE$)
        .body("$JSON_PATH$", equalTo($EXPECTED_VALUE$));
}

Selenium Page Object Method:

public $RETURN_TYPE$ $METHOD_NAME$($PARAMETERS$) {
    wait.until(ExpectedConditions.elementToBeClickable($ELEMENT$));
    $ELEMENT$.$ACTION$();
    return $RETURN_VALUE$;
}

TestNG Data Provider:

@DataProvider(name = "$PROVIDER_NAME$")
public Object[][] $METHOD_NAME$() {
    return new Object[][] {
        $DATA$
    };
}

Run Configurations for Test Execution

JUnit Run Configuration Template:

Name: All Unit Tests
Test kind: All in package
Package: com.example.tests.unit
VM options: -ea -Xmx512m
Working directory: $MODULE_DIR$
Environment variables: 
  ENV=test
  LOG_LEVEL=DEBUG
Before launch: Build, Run Maven Goal (clean compile)

TestNG Suite Configuration:

Name: Integration Tests
Suite: src/test/resources/testng-integration.xml
VM options: -Denv=staging -Dbrowser=chrome
Listeners: com.example.listeners.TestListener
Before launch: Build, Run Maven Goal (clean test-compile)

Debugging Test Failures

Conditional Breakpoints: Right-click on breakpoint and add condition:

username.equals("problematicUser") && response.getStatus() != 200

Evaluate Expression: During debugging, use Alt+F8 to evaluate:

// Check JSON response content
new ObjectMapper().readTree(response.getBody().asString())

// Verify element state
driver.findElement(By.id("submitBtn")).isEnabled()

// Database query verification
jdbcTemplate.queryForObject("SELECT COUNT(*) FROM users WHERE status = 'ACTIVE'", Integer.class)

Exception Breakpoints: Set breakpoints for specific exceptions:

Go to Run > View Breakpoints
Add Java Exception Breakpoints
Enter exception class (e.g., AssertionError, TimeoutException)

Code Analysis and Inspection

Enable useful inspections for test code:

Settings > Editor > Inspections > Enable:
- JUnit > Test method naming convention
- JUnit > Test method without assertions
- TestNG > Dependent methods
- Java > Probable bugs > Constant conditions
- Java > Testing > Assertion arguments order

Custom inspection profile for tests:

<!-- .idea/inspectionProfiles/Tests.xml -->
<profile version="1.0">
  <option name="myName" value="Tests" />
  <inspection_tool class="JUnitTestMethodWithNoAssertions" enabled="true" level="WARNING" />
  <inspection_tool class="TestMethodWithoutAssertion" enabled="true" level="WARNING" />
</profile>

Browser DevTools Mastery

Browser Developer Tools are essential for every tester, whether you’re debugging UI issues, analyzing network performance, or investigating JavaScript errors. Modern browsers (Chrome, Firefox, Safari, Edge) offer powerful built-in tools.

Chrome DevTools for Testing

1. Elements Panel

Inspecting DOM for Test Automation:

Right-click element → Inspect
Find unique selectors for automation
Copy XPath: Right-click element → Copy → Copy XPath
Copy JS Path: Right-click element → Copy → Copy JS path

Best Practices for Selector Generation:

// Instead of fragile XPath:
// /html/body/div[1]/div[2]/form/div[3]/button

// Use more stable selectors:
document.querySelector('[data-testid="submit-button"]')
document.querySelector('button[type="submit"].primary')

// Or relative XPath:
//button[contains(text(), 'Submit')]
//button[@data-testid='submit-button']

Live Edit for Testing:

Double-click attributes to modify
Edit as HTML for complex changes
Test CSS changes in Styles panel
Force element states: :hover, :active, :focus

2. Console Panel

Essential Console Commands for Testers:

// Query elements (similar to test automation)
$('button.submit')           // Returns first match (like querySelector)
$$('button')                 // Returns all matches (like querySelectorAll)
$x('//button[@type="submit"]') // XPath query

// Inspect elements
inspect($('button.submit'))  // Opens Elements panel

// Monitor events
monitorEvents($('form'), 'submit')  // Log form submission
unmonitorEvents($('form'))          // Stop monitoring

// Network monitoring
monitor(functionName)        // Log when function is called
unmonitor(functionName)

// Performance
console.time('operationName')
// ... code execution ...
console.timeEnd('operationName')  // Shows execution time

// Table display for data analysis
console.table(users)         // Display array of objects as table

// Test assertions
console.assert(value > 0, 'Value must be positive')

// Get event listeners
getEventListeners($('button.submit'))

// Copy data to clipboard
copy(JSON.stringify(userData))

Snippets for Reusable Test Scripts:

Create snippet in Sources > Snippets:

// Snippet: Check All Validation Errors
(function checkValidation() {
  const errors = $$('.error-message');
  console.table(errors.map(el => ({
    element: el.closest('[data-testid]')?.dataset.testid || 'unknown',
    message: el.textContent.trim(),
    visible: window.getComputedStyle(el).display !== 'none'
  })));
})();

// Snippet: Test Form Data
(function getFormData() {
  const form = $('form');
  const formData = new FormData(form);
  const data = {};
  for (let [key, value] of formData.entries()) {
    data[key] = value;
  }
  console.log('Form Data:', data);
  copy(JSON.stringify(data, null, 2));
  console.log('Copied to clipboard!');
})();

// Snippet: Find Orphaned Test IDs
(function findOrphanedTestIds() {
  const elements = $$('[data-testid]');
  const testIds = elements.map(el => ({
    id: el.dataset.testid,
    tag: el.tagName,
    text: el.textContent.trim().substring(0, 50)
  }));
  
  console.table(testIds);
  console.log(`Total: ${testIds.length} elements with test IDs`);
})();

3. Network Panel

Analyzing API Requests for Testing:

Filtering Requests:

Filter by type: XHR, Fetch, JS, CSS, Img
Filter by domain: domain:api.example.com
Filter by status: status-code:404
Filter by method: method:POST
Combine: method:POST domain:api status-code:200

Request Analysis:

Headers: Check authorization tokens, content types
Payload: Verify request body format
Preview: View response data structure
Response: Raw response data
Timing: Analyze request duration

Copy Request as Code: Right-click request → Copy → Copy as cURL / Copy as fetch / Copy as PowerShell

# Example cURL for test automation
curl 'https://api.example.com/users' \
  -H 'Authorization: Bearer eyJhbGc...' \
  -H 'Content-Type: application/json' \
  --data-raw '{"username":"testuser"}' \
  --compressed

HAR File Export for Bug Reports:

Right-click in Network panel
Save all as HAR
Attach to bug report for complete network trace

Throttling for Performance Testing:

Network panel > Throttling dropdown:
- Fast 3G (1.6 Mbps)
- Slow 3G (400 Kbps)
- Offline
- Custom profiles

4. Sources Panel for Debugging

JavaScript Debugging for Testers:

Breakpoint Types:

Line Breakpoints: Click line number
Conditional Breakpoints: Right-click line → Add conditional breakpoint
```
userId === 123 && response.status !== 200
```
DOM Breakpoints: Right-click element in Elements panel
- Break on subtree modifications
- Break on attribute modifications
- Break on node removal
Event Listener Breakpoints: Sources > Event Listener Breakpoints
- Mouse > click
- Keyboard > keydown
- Form > submit
- XHR > XMLHttpRequest sent
XHR/Fetch Breakpoints: Sources > XHR/fetch Breakpoints
- Add URL pattern: api/users

Local Overrides for Testing:

1. Sources > Overrides > Enable Local Overrides
2. Select folder for overrides
3. Edit response in Sources panel
4. Save (Ctrl+S)
5. Reload page to test modified response

Use cases:

Test error handling without backend changes
Modify API responses for edge cases
Test different data scenarios
Simulate slow/failed responses

Blackboxing Third-Party Scripts:

Settings > Blackboxing > Add pattern
Pattern: node_modules/

Improves debugging by skipping library code.

5. Performance Panel

Recording Performance for Test Analysis:

1. Click Record
2. Perform actions
3. Stop recording
4. Analyze:
   - FPS: Frames per second (smooth = 60 FPS)
   - CPU: JavaScript execution time
   - Network: Request waterfall
   - Screenshots: Visual timeline

Key Metrics for Testers:

FCP (First Contentful Paint): When first content appears
LCP (Largest Contentful Paint): When main content loaded
TTI (Time to Interactive): When page becomes interactive
TBT (Total Blocking Time): Time main thread is blocked
CLS (Cumulative Layout Shift): Visual stability

Performance Testing Script:

// Record performance metrics
const perfData = performance.getEntriesByType('navigation')[0];
console.table({
  'DNS Lookup': perfData.domainLookupEnd - perfData.domainLookupStart,
  'TCP Connection': perfData.connectEnd - perfData.connectStart,
  'Request Time': perfData.responseStart - perfData.requestStart,
  'Response Time': perfData.responseEnd - perfData.responseStart,
  'DOM Processing': perfData.domInteractive - perfData.responseEnd,
  'Total Load Time': perfData.loadEventEnd - perfData.navigationStart
});

// Get Web Vitals
const observer = new PerformanceObserver((list) => {
  for (const entry of list.getEntries()) {
    console.log(`${entry.name}: ${entry.value}`);
  }
});
observer.observe({ entryTypes: ['largest-contentful-paint', 'first-input', 'layout-shift'] });

6. Application Panel

Storage Inspection for Testing:

Local Storage / Session Storage:

// View in Console
console.table(Object.entries(localStorage))

// Test data manipulation
localStorage.setItem('authToken', 'test-token-123')
localStorage.removeItem('userId')
localStorage.clear()

// Test for automation
expect(localStorage (as discussed in [Test Management Systems: Jira vs TestRail vs Zephyr](/blog/test-management-systems-comparison)).getItem('theme')).toBe('dark')

Cookies:

View all cookies for domain
Edit cookie values
Delete individual cookies
Clear all cookies

IndexedDB:

Inspect database structure
View stored records
Delete databases for clean test state

Cache Storage:

Inspect Service Worker caches
View cached responses
Delete cache for testing

7. Lighthouse for Quality Testing

Run automated audits:

1. Open Lighthouse panel
2. Select categories:
   - Performance
   - Accessibility
   - Best Practices
   - SEO
   - Progressive Web App
3. Choose device (Mobile/Desktop)
4. Click "Generate report"

Command Line Lighthouse:

npm install -g lighthouse

# Run audit
lighthouse https://example.com --output html --output-path ./report.html

# With custom config
lighthouse https://example.com \
  --throttling.cpuSlowdownMultiplier=4 \
  --only-categories=performance,accessibility \
  --chrome-flags="--headless"

Firefox Developer Tools

Unique Features for Testers:

CSS Grid/Flexbox Inspector:

Visual overlay for Grid/Flexbox layouts
Better than Chrome for CSS debugging

Accessibility Inspector:

Tools > Browser Tools > Accessibility
- View accessibility tree
- Check ARIA attributes
- Simulate color blindness
- Check contrast ratios

Screenshot Command:

Open Developer Tools > Settings (F1) > Available Toolbox Buttons > Enable "Take a screenshot"

Or use Console:
:screenshot --fullpage
:screenshot --selector ".main-content"

Network Request Blocking:

Network panel > Right-click request > Block URL

Test error handling without backend changes.

Proxy Tools: Charles and Fiddler

Proxy tools intercept HTTP/HTTPS traffic between client and server, enabling testers to inspect, modify, and mock API responses. Essential for mobile testing, API testing, and security testing.

Charles Proxy

Charles is a cross-platform HTTP proxy / HTTP monitor / Reverse Proxy that enables developers and testers to view all HTTP/HTTPS traffic.

Installation and Setup

# macOS
brew install --cask charles

# Windows: Download from charlesproxy.com
# License: ~$50 (free trial available)

Initial Configuration:

Proxy > Proxy Settings
- Port: 8888 (default)
- Enable transparent HTTP proxying: ✓
Proxy > macOS Proxy (to set system proxy)

SSL Certificate Installation (for HTTPS decryption):

macOS:

1. Help > SSL Proxying > Install Charles Root Certificate
2. Open Keychain Access
3. Find "Charles Proxy" certificate
4. Double-click > Trust > Always Trust

Windows:

1. Help > SSL Proxying > Install Charles Root Certificate
2. Certificate will be added to Windows Certificate Store

Mobile Device (iOS/Android):

1. Connect device to same WiFi as computer
2. Device WiFi Settings > Configure Proxy > Manual
   - Server: [Computer IP]
   - Port: 8888
3. Open browser on device: chls.pro/ssl
4. Install certificate
5. iOS: Settings > General > About > Certificate Trust Settings > Enable

SSL Proxying Settings

Enable SSL proxying for specific hosts:

Proxy > SSL Proxying Settings > Add

Location:
  Host: *.example.com
  Port: 443

Or for all hosts:
  Host: *
  Port: 443

Recording and Analyzing Traffic

Structure View:

Hierarchical view of hosts and paths
Expand to see all requests to specific endpoint
Right-click > Clear to remove noise

Sequence View:

Chronological list of all requests
Better for understanding request flow
Shows exact timing of requests

Request/Response Inspector:

Tabs:

Overview: Method, status, timing, size
Headers: Request/response headers
Text: Plain text response
JSON: Formatted JSON with tree view
XML: Formatted XML
Raw: Complete raw request/response

Traffic Filtering

Focus on Specific Host:

Right-click host > Focus
Now only shows traffic for that host

Recording Settings:

Proxy > Recording Settings > Include

Add:
  Protocol: HTTP+HTTPS
  Host: api.example.com
  Port: 443
  Path: /api/*

Filter by Content Type:

View > Filter Settings

Show only:
☑ JSON
☑ XML
☐ HTML
☐ Images
☐ CSS/JavaScript

Request Manipulation

Breakpoints for Request/Response Modification:

1. Proxy > Breakpoint Settings > Enable Breakpoints
2. Add breakpoint:
   - Host: api.example.com
   - Path: /api/users
   - Request: ✓
   - Response: ✓

When request/response hits breakpoint:

Edit JSON Request tab: Modify request body
Edit Response tab: Modify response
Click Execute to continue

Use Cases:

Test error handling by changing status codes
Modify response data for edge cases
Change request parameters
Test timeout scenarios (add delay)

Map Local & Map Remote

Map Local (Replace remote response with local file):

Tools > Map Local Settings > Add

Map From:
  Protocol: HTTPS
  Host: api.example.com
  Path: /api/users
  
Map To:
  Local Path: /Users/test/mock-responses/users.json

Mock response file (users.json):

{
  "users": [
    {
      "id": 1,
      "name": "Test User",
      "email": "test@example.com",
      "role": "admin"
    }
  ],
  "total": 1
}

Map Remote (Redirect requests to different server):

Tools > Map Remote Settings > Add

Map From:
  Protocol: HTTPS
  Host: api-prod.example.com
  Path: /api/v2/users

Map To:
  Protocol: HTTPS
  Host: api-staging.example.com
  Path: /api/v2/users

Use cases:

Test against staging while using production frontend
Test new API version
Test load balancer behavior

Rewrite Tool

Modify Requests/Responses with Rules:

Tools > Rewrite Settings > Add

Name: Add CORS Headers
Apply to: api.example.com

Add Rule:
  Type: Add Header
  Where: Response
  Name: Access-Control-Allow-Origin
  Value: *

Add Rule:
  Type: Modify Status
  Where: Response
  Status: 200
  (Change 4xx/5xx to 200 for testing)

Add Rule:
  Type: Body Replacement
  Where: Response
  Match: "status":"active"
  Replace: "status":"inactive"

Throttling (Network Conditioning)

Proxy > Throttle Settings > Enable Throttling

Preset: 3G (780 kbps down, 330 kbps up)
Or Custom:
  Bandwidth: 512 kbps
  Utilisation: 80%
  Round-trip latency: 300ms
  MTU: 1500 bytes

Apply to: Only selected hosts
Add: api.example.com

Use Cases:

Test app behavior on slow networks
Test timeouts
Test loading states
Test progressive enhancement

Repeat Requests

Repeat Testing:

Right-click request > Repeat
Right-click request > Repeat Advanced
  - Count: 10
  - Concurrency: 5
  - Delay: 1000ms

Use for:

Load testing (basic)
Testing race conditions
Testing rate limiting
Reproducing intermittent issues

Export and Reporting

Export Session:

File > Export Session
Formats:
  - Charles Session (.chls)
  - HAR (HTTP Archive)
  - CSV
  - JSON

Generate Report:

File > Export Report
  - HTML Report
  - Include request/response bodies
  - Include timing information

Attach to bug reports for complete context.

Fiddler Classic / Fiddler Everywhere

Fiddler is another powerful web debugging proxy, popular on Windows. Fiddler Everywhere is the cross-platform version.

Installation

# Windows (Fiddler Classic - Free)
winget install Fiddler.Fiddler

# Cross-platform (Fiddler Everywhere - Subscription)
# Download from telerik.com/fiddler

Key Features

Composers: Create custom requests:

Composer > Parsed

Request:
  Method: POST
  URL: https://api.example.com/users
  Headers:
    Content-Type: application/json
    Authorization: Bearer {token}
  Body:
    {
      "username": "testuser",
      "email": "test@example.com"
    }

Execute > View response

AutoResponder (Similar to Charles Map Local):

Rules > Add Rule

If request matches:
  EXACT: https://api.example.com/users
Then respond with:
  File: C:\mocks\users.json
  Or: *404
  Or: *delay:5000 (5 second delay)
  Or: *bpu (break on request)

FiddlerScript (C# scripting):

// Auto-modify requests
static function OnBeforeRequest(oSession: Session) {
    // Add header to all API requests
    if (oSession.uriContains("/api/")) {
        oSession.oRequest["X-Test-Mode"] = "true";
    }
    
    // Block analytics
    if (oSession.uriContains("analytics.google.com")) {
        oSession.oRequest.FailSession(404, "Blocked", "");
    }
}

// Auto-modify responses
static function OnBeforeResponse(oSession: Session) {
    // Force CORS
    if (oSession.uriContains("/api/")) {
        oSession.oResponse["Access-Control-Allow-Origin"] = "*";
    }
    
    // Log slow responses
    if (oSession.Timers.ClientDoneResponse.Subtract(oSession.Timers.ClientBeginRequest).TotalMilliseconds > 2000) {
        FiddlerObject.log("Slow request: " + oSession.fullUrl);
    }
}

Filters:

Filters tab:

Hosts:
  Show only: api.example.com
  Hide: cdn.example.com

Client Process:
  Show only: chrome.exe

Breakpoints:
  Break request on POST
  Break response on status 500

Request Builder: More advanced than Composer:

Request Builder > New Request

Templates:
  - REST API GET
  - REST API POST with JSON
  - SOAP Request
  - GraphQL Query

Save as collection for reuse

Comparing Charles vs Fiddler

Feature	Charles	Fiddler Classic	Fiddler Everywhere
Platform	Mac, Windows, Linux	Windows only	Mac, Windows, Linux
Price	$50 (perpetual)	Free	$150/year subscription
UI	Native (Java Swing)	Native (WinForms)	Electron (modern)
Learning Curve	Medium	Medium	Easy
Performance	Good	Excellent	Good
Scripting	Limited	C# (powerful)	JavaScript
SSL Setup	Easy	Easy	Easiest
Mobile Testing	Excellent	Excellent	Excellent
Request Mocking	Map Local/Remote	AutoResponder	Mock Server
Network Throttling	Yes	Yes	Yes
API Testing	Basic	Composer	Advanced (collections)
Best For	Mac users, simplicity	Windows power users	Teams, cross-platform

Mobile Testing Workflow

Complete mobile testing setup:

Configure Proxy on Device:

iOS:
  Settings > Wi-Fi > [Network] > Configure Proxy
  Manual: [Computer IP]:8888

Android:
  Settings > Wi-Fi > [Network] > Advanced
  Proxy: Manual
  Hostname: [Computer IP]
  Port: 8888

Install SSL Certificate (see Charles setup above)
Enable SSL Proxying for app domains
Common Mobile Testing Scenarios:

Test API Error Handling:

Use Breakpoints to change response status to 500
Verify app shows appropriate error message
Check if retry mechanism works

Test Offline Mode:

Use Map Local to return cached responses
Block specific requests
Verify offline functionality

Test Different API Versions:

Use Map Remote to point to different API versions
Test backward compatibility
Test migration scenarios

Test Slow Networks:

Apply throttling (3G settings)
Verify loading states
Check timeout handling
Test progressive image loading

Capture for Bug Reports:

Record complete session
Export HAR file
Include in bug report with steps to reproduce

Choosing the Right Tools

IDE Selection Matrix

Use Case	VS Code	IntelliJ IDEA
JavaScript/TypeScript tests	✓✓✓ Excellent	✓✓ Good
Java test automation	✓ Basic	✓✓✓ Excellent
Python testing	✓✓✓ Excellent (with extensions)	✓✓ Good (PyCharm better)
Multi-language projects	✓✓✓ Excellent	✓✓ Good
Lightweight/Fast startup	✓✓✓ Excellent	✓ Slower
Built-in features	✓ Needs extensions	✓✓✓ Excellent
Free/Open source	✓✓✓ Free	✓ Community Edition
API testing	✓✓ Good (extensions)	✓✓✓ Built-in

Recommended Tool Combinations

Frontend Test Automation:

IDE: VS Code
Extensions: Playwright, Jest, ESLint
Browser: Chrome DevTools
Proxy: Charles

Backend API Testing:

IDE: IntelliJ IDEA / VS Code
Tools: REST Client, Postman
Proxy: Charles / Fiddler
Database: DBeaver / IntelliJ Database Tools

Mobile Testing:

IDE: VS Code / Android Studio
Proxy: Charles (best mobile support)
Device Mirroring: scrcpy
Performance: Chrome DevTools (remote debugging)

Full Stack Testing:

IDE: VS Code (multi-root workspace)
Browser: Chrome DevTools
API: IntelliJ HTTP Client / Thunder Client
Proxy: Charles

Learning Path

Week 1-2: IDE Basics

Set up VS Code or IntelliJ IDEA
Install essential extensions/plugins
Learn keyboard shortcuts
Configure debugging
Create custom snippets

Week 3-4: Browser DevTools

Master Elements and Console panels
Learn Network analysis
Practice JavaScript debugging
Create reusable snippets
Run Lighthouse audits

Week 5-6: Proxy Tools

Install and configure Charles/Fiddler
Set up SSL proxying
Practice request modification
Create mock responses with Map Local
Test mobile apps

Week 7-8: Advanced Techniques

Combine tools in testing workflow
Create automated test helpers
Build custom debugging scripts
Document team best practices
Train other team members

Productivity Tips

1. Keyboard Shortcuts Learn these first:

VS Code: Cmd/Ctrl + P (quick open), Cmd/Ctrl + Shift + P (command palette)
DevTools: Cmd/Ctrl + Shift + C (inspect element), Cmd + K (clear console)
Charles: Cmd/Ctrl + K (clear session), Cmd/Ctrl + R (start/stop recording)

2. Custom Snippets Create snippets for:

Common test patterns
API request templates
Console debugging scripts
Mock data generators

3. Workspace Organization

Use multi-root workspaces for complex projects
Create .vscode/tasks.json for common operations
Save debugging configurations
Organize proxy sessions by feature

4. Documentation Document in your team wiki:

IDE setup instructions
Required extensions/plugins
Debugging configurations
Proxy setup for projects
Common troubleshooting steps

5. Automation Automate repetitive tasks:

Test execution scripts
Coverage report generation
HAR file analysis scripts
Network performance monitoring

Conclusion

Mastering the right tools transforms testing efficiency. VS Code and IntelliJ IDEA provide powerful environments for test development with the right extensions and configurations. Browser DevTools offer unmatched insight into application behavior. Proxy tools like Charles and Fiddler enable deep API inspection and manipulation.

The key is not to learn every feature of every tool, but to:

Choose tools that fit your tech stack
Master the features you use daily (80/20 rule)
Automate repetitive tasks with snippets and scripts
Document your setup for team consistency
Continuously learn as tools evolve

Start with one tool from each category (IDE, DevTools, Proxy), build proficiency, then expand your toolkit. Remember: tools are force multipliers, but testing expertise is what matters most.

Next Steps:

Set up your primary IDE with essential extensions today
Practice browser DevTools daily during testing
Install and configure a proxy tool this week
Create your first custom snippet or debugging configuration
Share your learnings with your team

Happy testing!

Table of Contents

VS Code for QA Engineers

Essential Extensions for Testers

1. Test Runner Extensions

2. Code Quality and Linting

3. API Testing Extensions

4. Debugging and Inspection

5. Version Control and Collaboration

Custom Snippets for Test Automation

Workspace Configuration for Test Projects

Tasks for Common Testing Operations

Keyboard Shortcuts for Productivity

Multi-Root Workspaces for Complex Projects

IntelliJ IDEA for Testing

Essential Plugins for Testing

1. Test Automation Plugins

2. Code Coverage Tools

3. REST API Testing

4. Database Tools Integration

Live Templates for Test Code

Run Configurations for Test Execution

Debugging Test Failures

Code Analysis and Inspection

Browser DevTools Mastery

Chrome DevTools for Testing

1. Elements Panel

2. Console Panel

3. Network Panel

4. Sources Panel for Debugging

5. Performance Panel

6. Application Panel

7. Lighthouse for Quality Testing

Firefox Developer Tools

Proxy Tools: Charles and Fiddler

Charles Proxy

Installation and Setup

SSL Proxying Settings

Recording and Analyzing Traffic

Traffic Filtering

Request Manipulation

Map Local & Map Remote

Rewrite Tool

Throttling (Network Conditioning)

Repeat Requests

Export and Reporting

Fiddler Classic / Fiddler Everywhere

Installation

Key Features

Comparing Charles vs Fiddler

Mobile Testing Workflow

Choosing the Right Tools

IDE Selection Matrix

Recommended Tool Combinations

Learning Path

Productivity Tips

Conclusion