Testing - Modrinth

Overview

Modrinth uses a comprehensive testing strategy across both frontend (TypeScript/Vue) and backend (Rust) codebases.

Test Types

Type	Purpose	Tools
Unit Tests	Test individual functions/components	Vitest (JS), cargo test (Rust)
Integration Tests	Test interactions between modules	cargo test, Playwright
E2E Tests	Test full user workflows	Playwright
Linting	Code quality and style	ESLint, Clippy
Type Checking	TypeScript type safety	tsc

Frontend Testing (TypeScript/Vue)

Running Tests

# Run all frontend tests
pnpm test

# Run tests for specific package
pnpm --filter @modrinth/frontend test
pnpm --filter @modrinth/ui test

# Run in watch mode
pnpm --filter @modrinth/frontend test --watch

Unit Tests (Vitest)

Frontend tests use Vitest for fast unit testing.

Component Testing

src/components/ProjectCard.test.ts

import { describe, it, expect } from 'vitest'
import { mount } from '@vue/test-utils'
import ProjectCard from './ProjectCard.vue'

describe('ProjectCard', () => {
	it('renders project title', () => {
		const wrapper = mount(ProjectCard, {
			props: {
				project: {
					id: '1',
					title: 'Sodium',
					description: 'Performance mod',
					downloads: 10000000,
				},
			},
		})

		expect(wrapper.text()).toContain('Sodium')
		expect(wrapper.text()).toContain('Performance mod')
	})

	it('emits click event', async () => {
		const wrapper = mount(ProjectCard, {
			props: { project: { id: '1', title: 'Test' } },
		})

		await wrapper.trigger('click')
		expect(wrapper.emitted('click')).toBeTruthy()
	})
})

Utility Function Testing

src/helpers/format.test.ts

import { describe, it, expect } from 'vitest'
import { formatNumber, formatDate } from './format'

describe('formatNumber', () => {
	it('formats large numbers', () => {
		expect(formatNumber(1234567)).toBe('1.2M')
		expect(formatNumber(1234)).toBe('1.2K')
		expect(formatNumber(123)).toBe('123')
	})
})

describe('formatDate', () => {
	it('formats relative dates', () => {
		const now = new Date()
		const hourAgo = new Date(now.getTime() - 60 * 60 * 1000)
		expect(formatDate(hourAgo)).toBe('1 hour ago')
	})
})

Composable Testing

src/composables/useProject.test.ts

import { describe, it, expect, vi } from 'vitest'
import { useProject } from './useProject'
import { flushPromises } from '@vue/test-utils'

vi.mock('@modrinth/api-client', () => ({
	labrinth: {
		projects_v3: {
			get: vi.fn().mockResolvedValue({
				id: 'sodium',
				title: 'Sodium',
			}),
		},
	},
}))

describe('useProject', () => {
	it('fetches project data', async () => {
		const { project, loading } = useProject('sodium')

		expect(loading.value).toBe(true)
		await flushPromises()

		expect(loading.value).toBe(false)
		expect(project.value?.title).toBe('Sodium')
	})
})

E2E Tests (Playwright)

End-to-end tests simulate real user interactions.

tests/e2e/project-page.spec.ts

import { test, expect } from '@playwright/test'

test('project page displays correctly', async ({ page }) => {
	await page.goto('/mod/sodium')

	// Check title is visible
	await expect(page.locator('h1')).toContainText('Sodium')

	// Check download button
	const downloadBtn = page.locator('button:has-text("Download")')
	await expect(downloadBtn).toBeVisible()

	// Click version dropdown
	await page.click('[data-testid="version-selector"]')
	await expect(page.locator('.version-list')).toBeVisible()
})

test('search functionality', async ({ page }) => {
	await page.goto('/')

	// Type in search
	await page.fill('input[type="search"]', 'optimization')
	await page.press('input[type="search"]', 'Enter')

	// Wait for results
	await page.waitForSelector('.project-card')

	// Verify results
	const cards = await page.locator('.project-card').count()
	expect(cards).toBeGreaterThan(0)
})

Run E2E tests:

# Install Playwright
pnpm exec playwright install

# Run tests
pnpm --filter @modrinth/frontend test:e2e

# Run with UI
pnpm exec playwright test --ui

Linting

# Run ESLint
pnpm lint

# Auto-fix issues
pnpm fix

# Lint specific package
pnpm --filter @modrinth/frontend lint

Type Checking

# Check types (all packages)
pnpm type-check

# Check specific package
pnpm --filter @modrinth/frontend type-check

Backend Testing (Rust)

Running Tests

# Run all tests (from root)
cargo test --workspace

# Run Labrinth tests
cargo test -p labrinth --all-targets

# Run app tests (Theseus)
cargo test -p theseus --all-targets

# Run specific test
cargo test -p labrinth test_create_project

# Run with output
cargo test -p labrinth -- --nocapture

# Run in parallel (faster)
cargo test -p labrinth -- --test-threads=4

Unit Tests

apps/labrinth/src/models/project.rs

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_project_slug_validation() {
        assert!(is_valid_slug("my-mod"));
        assert!(is_valid_slug("my_mod"));
        assert!(!is_valid_slug("My Mod"));  // Spaces not allowed
        assert!(!is_valid_slug("my-mod!"));  // Special chars not allowed
    }

    #[test]
    fn test_project_type_parsing() {
        assert_eq!(ProjectType::from_str("mod"), Ok(ProjectType::Mod));
        assert_eq!(ProjectType::from_str("modpack"), Ok(ProjectType::Modpack));
        assert!(ProjectType::from_str("invalid").is_err());
    }
}

Integration Tests

Integration tests go in src/test/ or tests/ directory.

apps/labrinth/src/test/project.rs

use actix_web::test;
use sqlx::PgPool;

#[actix_rt::test]
async fn test_create_and_get_project() {
    // Setup test database
    let pool = setup_test_db().await;
    
    // Create project
    let project = create_project(
        "test-mod",
        "Test Mod",
        &pool,
    ).await.unwrap();
    
    assert_eq!(project.slug, "test-mod");
    assert_eq!(project.title, "Test Mod");
    
    // Fetch project
    let fetched = get_project(&project.id, &pool).await.unwrap();
    assert_eq!(fetched.id, project.id);
    
    // Cleanup
    cleanup_test_db(&pool).await;
}

#[actix_rt::test]
async fn test_project_not_found() {
    let pool = setup_test_db().await;
    
    let result = get_project("nonexistent", &pool).await;
    assert!(result.is_err());
    
    cleanup_test_db(&pool).await;
}

API Route Tests

apps/labrinth/src/test/routes.rs

use actix_web::{test, App};
use crate::routes::v3;

#[actix_rt::test]
async fn test_get_project_endpoint() {
    let pool = setup_test_db().await;
    let app = test::init_service(
        App::new()
            .app_data(web::Data::new(pool.clone()))
            .configure(v3::projects::config)
    ).await;
    
    let req = test::TestRequest::get()
        .uri("/v3/project/sodium")
        .to_request();
    
    let resp = test::call_service(&app, req).await;
    assert_eq!(resp.status(), 200);
    
    let body: Project = test::read_body_json(resp).await;
    assert_eq!(body.slug, "sodium");
}

#[actix_rt::test]
async fn test_create_project_requires_auth() {
    let app = test::init_service(
        App::new().configure(v3::projects::config)
    ).await;
    
    let req = test::TestRequest::post()
        .uri("/v3/project")
        .set_json(&json!({
            "title": "Test",
            "slug": "test",
        }))
        .to_request();
    
    let resp = test::call_service(&app, req).await;
    assert_eq!(resp.status(), 401);  // Unauthorized
}

Database Tests

apps/labrinth/src/test/database.rs

use sqlx::{PgPool, postgres::PgPoolOptions};

pub async fn setup_test_db() -> PgPool {
    let pool = PgPoolOptions::new()
        .max_connections(5)
        .connect("postgres://labrinth:labrinth@localhost/labrinth_test")
        .await
        .expect("Failed to connect to test database");
    
    // Run migrations
    sqlx::migrate!("./migrations")
        .run(&pool)
        .await
        .expect("Failed to run migrations");
    
    pool
}

pub async fn cleanup_test_db(pool: &PgPool) {
    // Truncate all tables
    sqlx::query!("TRUNCATE TABLE projects CASCADE")
        .execute(pool)
        .await
        .expect("Failed to cleanup database");
}

Benchmark Tests

benches/search_benchmark.rs

use criterion::{black_box, criterion_group, criterion_main, Criterion};
use labrinth::search::search_projects;

fn benchmark_search(c: &mut Criterion) {
    c.bench_function("search projects", |b| {
        b.iter(|| {
            search_projects(
                black_box("optimization"),
                black_box(vec!["mod"]),
                black_box(20),
            )
        });
    });
}

criterion_group!(benches, benchmark_search);
criterion_main!(benches);

Run benchmarks:

cargo bench -p labrinth

Linting (Clippy)

# Run clippy
cargo clippy -p labrinth --all-targets
cargo clippy -p theseus --all-targets

# Run clippy with warnings as errors (CI mode)
cargo clippy -p labrinth --all-targets -- -D warnings

Zero warnings required - CI will fail if there are any clippy warnings.

Code Formatting

# Check formatting
cargo fmt --check

# Auto-format
cargo fmt

Test Coverage

Frontend Coverage

# Generate coverage report
pnpm --filter @modrinth/frontend test --coverage

# Open coverage report
open coverage/index.html

Backend Coverage (Tarpaulin)

# Install tarpaulin
cargo install cargo-tarpaulin

# Generate coverage
cargo tarpaulin -p labrinth --out Html

# Open report
open tarpaulin-report.html

CI/CD Testing

GitHub Actions runs tests automatically on:

Every push to any branch
Every pull request
Merge queue checks

CI Workflow

.github/workflows/check-rust.yml

name: Check Rust

on:
  push:
  pull_request:

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      
      - uses: dtolnay/rust-toolchain@stable
      
      - name: Run tests
        run: cargo test --workspace --all-targets
      
      - name: Run clippy
        run: cargo clippy --workspace --all-targets -- -D warnings
      
      - name: Check formatting
        run: cargo fmt --check

Frontend CI

.github/workflows/check-generic.yml

name: Check Frontend

on:
  push:
  pull_request:

jobs:
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      
      - uses: pnpm/action-setup@v2
        with:
          version: 9.15.0
      
      - uses: actions/setup-node@v4
        with:
          node-version: 20
          cache: 'pnpm'
      
      - run: pnpm install
      
      - run: pnpm lint
      
      - run: pnpm type-check
      
      - run: pnpm test

Pre-PR Checklist

Before opening a pull request, ensure:

Frontend Checks

# Run all pre-PR checks
pnpm prepr

# Or run specific checks:
pnpm prepr:frontend:web   # Website
pnpm prepr:frontend:app   # Desktop app
pnpm prepr:frontend:lib   # Shared libraries

This runs:

ESLint
Prettier
TypeScript type checking
Tests

Backend Checks (Labrinth)

cd apps/labrinth

# Clippy (ZERO warnings required)
cargo clippy -p labrinth --all-targets

# Format check
cargo fmt --check

# Prepare SQLx cache
cargo sqlx prepare

# Tests (optional - takes time)
cargo test -p labrinth --all-targets

Build Verification

# Ensure everything builds
pnpm build

Testing Best Practices

General Principles

Test behavior, not implementation - Focus on what code does, not how it does it
Keep tests simple - One assertion per test when possible
Use descriptive names - Test names should explain what they test
Avoid test interdependence - Tests should run independently
Mock external dependencies - Don’t hit real APIs or databases in unit tests

Frontend Best Practices

// Good: Test user-facing behavior
it('displays error message when login fails', async () => {
	const wrapper = mount(LoginForm)
	await wrapper.find('form').trigger('submit')
	expect(wrapper.text()).toContain('Invalid credentials')
})

// Bad: Test implementation details
it('sets errorMessage state to string', async () => {
	const wrapper = mount(LoginForm)
	await wrapper.vm.handleSubmit()
	expect(wrapper.vm.errorMessage).toBe('Invalid credentials')
})

Backend Best Practices

// Good: Descriptive test name
#[test]
fn test_project_slug_rejects_special_characters() {
    assert!(!is_valid_slug("my-mod!"));
}

// Bad: Unclear test name
#[test]
fn test_slug() {
    assert!(!is_valid_slug("my-mod!"));
}

Mocking

Frontend:

import { vi } from 'vitest'

vi.mock('@modrinth/api-client', () => ({
	labrinth: {
		projects_v3: {
			get: vi.fn().mockResolvedValue({ id: '1', title: 'Test' }),
		},
	},
}))

Rust:

use mockall::predicate::*;
use mockall::mock;

mock! {
    pub Database {
        async fn get_project(&self, id: &str) -> Result<Project, Error>;
    }
}

Debugging Tests

Frontend

# Run specific test
pnpm test -- ProjectCard.test.ts

# Run in watch mode
pnpm test -- --watch

# Run with browser DevTools (Playwright)
pnpm exec playwright test --debug

Backend

# Run specific test with output
cargo test test_create_project -- --nocapture

# Run with backtrace
RUST_BACKTRACE=1 cargo test

# Run with logging
RUST_LOG=debug cargo test

Performance Testing

Load Testing (Backend)

Use tools like k6 or Apache Bench:

# Apache Bench: 1000 requests, 10 concurrent
ab -n 1000 -c 10 http://localhost:8000/v3/project/sodium

# k6 load test
k6 run load-test.js

load-test.js

import http from 'k6/http'
import { check } from 'k6'

export const options = {
	vus: 10,
	duration: '30s',
}

export default function () {
	const res = http.get('http://localhost:8000/v3/project/sodium')
	check(res, {
		'status is 200': (r) => r.status === 200,
		'response time < 500ms': (r) => r.timings.duration < 500,
	})
}

Next Steps

Code Style

Follow coding standards and conventions

Local Setup

Set up local development environment

Deployment

Learn about CI/CD and deployment

Contributing

Submit your first pull request

​Overview

​Test Types

​Frontend Testing (TypeScript/Vue)

​Running Tests

​Unit Tests (Vitest)

​Component Testing

​Utility Function Testing

​Composable Testing

​E2E Tests (Playwright)

​Linting

​Type Checking

​Backend Testing (Rust)

​Running Tests

​Unit Tests

​Integration Tests

​API Route Tests

​Database Tests

​Benchmark Tests

​Linting (Clippy)

​Code Formatting

​Test Coverage

​Frontend Coverage

​Backend Coverage (Tarpaulin)

​CI/CD Testing

​CI Workflow

​Frontend CI

​Pre-PR Checklist

​Testing Best Practices

​General Principles

​Frontend Best Practices

​Backend Best Practices

​Mocking

​Debugging Tests

​Frontend

​Backend

​Performance Testing

​Load Testing (Backend)

​Next Steps

Code Style

Local Setup

Deployment

Contributing

Overview

Test Types

Frontend Testing (TypeScript/Vue)

Running Tests

Unit Tests (Vitest)

Component Testing

Utility Function Testing

Composable Testing

E2E Tests (Playwright)

Linting

Type Checking

Backend Testing (Rust)

Running Tests

Unit Tests

Integration Tests

API Route Tests

Database Tests

Benchmark Tests

Linting (Clippy)

Code Formatting

Test Coverage

Frontend Coverage

Backend Coverage (Tarpaulin)

CI/CD Testing

CI Workflow

Frontend CI

Pre-PR Checklist

Testing Best Practices

General Principles

Frontend Best Practices

Backend Best Practices

Mocking

Debugging Tests

Frontend

Backend

Performance Testing

Load Testing (Backend)

Next Steps