FileMock is a web application that generates perfect test files for your development and testing needs. This quick start guide gets you up and running in 5 minutes.

What is FileMock?

FileMock generates realistic test files directly in your browser - completely client-side with instant file generation for comprehensive testing.

Perfect for:

Unit test fixtures
E2E testing scenarios
Performance testing with large files
Edge case validation
Security testing with malformed files

Step 1: Access FileMock

Visit filemock.com
No signup required - start generating files immediately
100% client-side - your data never leaves your browser

Step 2: Generate Your First Test File

Basic Image Generation

Select file type: Choose "Image" from the format selector
Set properties:
- Size: 500KB (good for basic testing)
- Format: JPEG
- Dimensions: 1200x800px
Click "Generate File"
Download the generated file to your project

Advanced Options

FileMock offers powerful customization:

File Size Options:
├── Tiny (1KB - 10KB)     - Icon testing
├── Small (10KB - 100KB)  - Thumbnail testing
├── Medium (100KB - 1MB)  - Standard uploads
├── Large (1MB - 10MB)    - Performance testing
└── Huge (10MB+)          - Stress testing

Step 3: Organize Your Test Files

Recommended Folder Structure

your-project/
├── tests/
│   └── fixtures/
│       └── filemock-files/
│           ├── images/
│           │   ├── valid-small.jpg
│           │   ├── valid-large.png
│           │   └── invalid-corrupted.jpg
│           ├── documents/
│           │   ├── small-pdf.pdf
│           │   └── large-docx.docx
│           └── edge-cases/
│               ├── empty-file.txt
│               ├── oversized.jpg
│               └── malformed.pdf

File Naming Convention

Use descriptive names that indicate purpose:

# Good naming examples
filemock-valid-jpeg-500kb.jpg
filemock-oversized-image-15mb.png
filemock-corrupted-pdf.pdf
filemock-empty-document.docx

# Include in filename:
- filemock- prefix (identifies source)
- purpose (valid/invalid/oversized)
- format (jpeg/png/pdf)
- size (500kb/15mb)

Step 4: Integration Examples

Jest Integration

// tests/fileUpload.test.js
import fs from "fs";
import path from "path";

const loadFileMockFile = (filename) => {
  const filePath = path.join(__dirname, "fixtures/filemock-files", filename);
  const buffer = fs.readFileSync(filePath);
  return new File([buffer], filename, { type: "image/jpeg" });
};

test("handles FileMock generated files", () => {
  const testFile = loadFileMockFile("filemock-valid-jpeg-500kb.jpg");
  expect(testFile.size).toBe(512000); // 500KB
  expect(testFile.type).toBe("image/jpeg");
});

Cypress Integration

// cypress/e2e/fileUpload.cy.js
describe("File Upload with FileMock", () => {
  it("uploads FileMock generated file", () => {
    cy.visit("/upload");

    // Use FileMock generated file
    cy.get('[data-testid="file-input"]').selectFile("cypress/fixtures/filemock-files/filemock-valid-jpeg-500kb.jpg");

    cy.get('[data-testid="upload-button"]').click();
    cy.contains("Upload successful").should("be.visible");
  });
});

Step 5: Testing Scenarios with FileMock

Comprehensive Test Suite

Generate files for different scenarios:

1. Happy Path Testing

# Generate standard files
- 100KB JPEG image
- 2MB PNG image
- 500KB PDF document

2. Edge Case Testing

# Generate boundary cases
- 1KB minimum file
- 10MB maximum file
- Empty file (0 bytes)

3. Error Scenario Testing

# Generate problematic files
- Oversized file (exceeds limits)
- Corrupted file structure
- Wrong file extension

4. Performance Testing

# Generate load testing files
- 50MB large image
- 100MB video file
- Multiple 5MB files

Pro Tips

Batch Generation Workflow

Plan your test scenarios first
Generate all files in one FileMock session
Download and organize immediately
Document file purposes in your test comments

File Management

// Create a FileMock file registry
const FILEMOCK_FILES = {
  validImage: "filemock-valid-jpeg-500kb.jpg",
  largeImage: "filemock-large-png-5mb.png",
  invalidFile: "filemock-corrupted-image.jpg",
  oversizedFile: "filemock-oversized-15mb.jpg",
};

// Use in tests
const testFile = loadFileMockFile(FILEMOCK_FILES.validImage);

Version Control

# Include FileMock files in git for team consistency
git add tests/fixtures/filemock-files/
git commit -m "Add FileMock test files for upload testing"

Next Steps

Explore Advanced Features: Try different file formats and sizes
Build Test Suites: Create comprehensive test scenarios
Team Integration: Share FileMock files with your team
Automate: Include FileMock file generation in your CI/CD workflow

Common Use Cases

Frontend Testing

Upload component validation
File preview functionality
Drag & drop interactions
Progress indicator testing

Backend Testing

File processing endpoints
Storage integration
File validation logic
Performance under load

Security Testing

Malicious file detection
File type validation
Size limit enforcement
Content scanning

FileMock makes it easy to test all these scenarios with realistic, consistent test data generated instantly in your browser.

FileMock

FileMock Quick Start Guide