Playwright for .NET Testing

This skill provides guidance for end-to-end (E2E) testing with Playwright for .NET using Microsoft.Playwright.MSTest.v4 integration in this .NET 10 project.

Table of Contents

1. Overview
2. Project Setup
3. Installing Browsers
4. Writing Tests
5. Selectors and Assertions
6. Debugging Tests
7. CI/CD Integration
8. Troubleshooting
9. Quick Reference

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Overview

What is Playwright?

Playwright is a modern E2E testing framework for web applications. It supports:

• Multiple browsers: Chromium, Firefox, WebKit
• Cross-platform: Windows, Linux, macOS
• Auto-waiting: Smart waits for elements
• Powerful selectors: CSS, text, accessibility
• Reliable: Reduces flakiness
• Fast: Parallel execution

Microsoft.Playwright.MSTest.v4

This project uses the MSTest integration which provides:

• PageTest base class - one browser context per test
• ContextTest base class - browser context with multiple pages
• BrowserTest base class - full browser control
• Built-in fixtures (Page, Context, Browser)
• Automatic cleanup

Version: 1.55.0-beta-4 (configured in Directory.Packages.props)

---

Project Setup

Current Playwright Projects

This repository has 2 Playwright test projects:

• tests/ClaudeStack.Web.Tests.Playwright/ - Tests for MVC application
• tests/ClaudeStack.API.Tests.Playwright/ - Tests for API application

Project Configuration

Both projects use this configuration:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <EnableMSTestRunner>true</EnableMSTestRunner>
    <OutputType>Exe</OutputType>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Playwright.MSTest.v4" />
    <PackageReference Include="MSTest" />
  </ItemGroup>
</Project>

Key points:

• Uses Microsoft.Testing.Platform (see mstest-testing-platform skill)
• Package versions managed in Directory.Packages.props (see dotnet-centralized-packages skill)
• MSTestSettings.cs configures method-level parallelization

Creating New Playwright Project

# Step 1: Create MSTest project
dotnet new mstest -o tests/Example.NewApp.Tests.Playwright

# Step 2: Edit .csproj to add required properties
# <PropertyGroup>
#   <EnableMSTestRunner>true</EnableMSTestRunner>
#   <OutputType>Exe</OutputType>
# </PropertyGroup>

# Step 3: Add Playwright package reference (version in Directory.Packages.props)
# <PackageReference Include="Microsoft.Playwright.MSTest.v4" />
# <PackageReference Include="MSTest" />

# Step 4: Install browsers (see next section)

# Step 5: Add MSTestSettings.cs with parallelization
# [assembly: Parallelize(Scope = ExecutionScope.MethodLevel)]

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Installing Browsers

Initial Browser Installation

After creating a Playwright project or after building, install browsers:

# Navigate to the build output directory
cd tests/ClaudeStack.Web.Tests.Playwright/bin/Debug/net10.0

# Run the Playwright PowerShell script
./playwright.ps1 install

Important: Browsers must be installed after building the project because the playwright.ps1 script is generated during build.

Installation on Different Platforms

Windows (PowerShell):

pwsh -Command "cd tests/ClaudeStack.Web.Tests.Playwright/bin/Debug/net10.0; ./playwright.ps1 install"

Linux/macOS (Bash):

pwsh tests/ClaudeStack.Web.Tests.Playwright/bin/Debug/net10.0/playwright.ps1 install

Installing Specific Browsers

# Install only Chromium
./playwright.ps1 install chromium

# Install Chromium and Firefox
./playwright.ps1 install chromium firefox

# Install with dependencies (for Linux CI)
./playwright.ps1 install --with-deps

Browser Locations

Browsers are installed in:

• Windows: %USERPROFILE%\AppData\Local\ms-playwright
• Linux: ~/.cache/ms-playwright
• macOS: ~/Library/Caches/ms-playwright

---

Writing Tests

Basic Test Structure

All tests inherit from PageTest:

using System.Threading.Tasks;
using Microsoft.Playwright.MSTest;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace ClaudeStack.Web.Tests.Playwright;

[TestClass]
public class HomePageTests : PageTest
{
    [TestMethod]
    public async Task HomePageLoadsSuccessfully()
    {
        await Page.GotoAsync("https://localhost:5001");

        await Expect(Page).ToHaveTitleAsync("Home Page");
    }
}

Key points:

• Inherit from PageTest
• Test methods are async Task
• Page property available automatically
• Expect for assertions

PageTest Fixtures

PageTest provides automatic fixtures:

public class MyTests : PageTest
{
    // Available properties:
    // - Page: IPage (automatically created per test)
    // - Context: IBrowserContext
    // - Browser: IBrowser
    // - Playwright: IPlaywright
}

Test Initialization

Use [TestInitialize] and [TestCleanup] as needed. Page is automatically disposed.

---

Selectors and Assertions

Selectors

Page.Locator("css")                              // CSS selector
Page.Locator("text=Get Started")                 // Text
Page.GetByTestId("id")                           // Test ID
Page.GetByRole(AriaRole.Button)                  // Accessibility
Page.GetByLabel("Email")                         // Form label
Page.Locator("div").Locator("button")            // Chaining

Assertions

await Expect(Page).ToHaveTitleAsync("Title");
await Expect(element).ToBeVisibleAsync();
await Expect(element).ToHaveTextAsync("text");
await Expect(element).ToHaveAttributeAsync("href", "/about");

Actions

await element.ClickAsync();
await element.FillAsync("value");
await element.CheckAsync();
await element.SelectOptionAsync("option");

---

Debugging Tests

Headed Mode

$env:HEADED="1"
dotnet run --project tests/ClaudeStack.Web.Tests.Playwright

Screenshots and Tracing

// Screenshot
await Page.ScreenshotAsync(new() { Path = "screenshot.png" });

// Tracing
await Context.Tracing.StartAsync(new() { Screenshots = true, Snapshots = true });
// ... test actions ...
await Context.Tracing.StopAsync(new() { Path = "trace.zip" });

View trace: pwsh .../playwright.ps1 show-trace trace.zip

Playwright Inspector

$env:PWDEBUG="1"
dotnet run --project tests/ClaudeStack.Web.Tests.Playwright

---

CI/CD Integration

# Azure DevOps / GitHub Actions
- Build project: dotnet build tests/**/*.Playwright.csproj
- Install browsers: pwsh .../playwright.ps1 install --with-deps
- Run tests: dotnet run --project tests/ClaudeStack.Web.Tests.Playwright

Important: Use --with-deps flag in CI to install system dependencies (Linux).

---

Troubleshooting

Issue: Browsers Not Installed

Error: "Executable doesn't exist at..."

Solution: Install browsers after building:

cd tests/ClaudeStack.Web.Tests.Playwright/bin/Debug/net10.0
./playwright.ps1 install

Issue: playwright.ps1 Not Found

Cause: Project not built yet.

Solution: Build first, then install browsers:

dotnet build tests/ClaudeStack.Web.Tests.Playwright
# Then install browsers

Issue: Tests Timeout

Cause: Default timeout (30s) exceeded.

Solution: Increase timeout:

[TestMethod]
[Timeout(60000)]  // 60 seconds
public async Task SlowTest()
{
    // Or set per-action timeout:
    await Page.GotoAsync("https://example.com", new() { Timeout = 60000 });
}

Issue: Element Not Found

Solution: Playwright auto-waits, but verify selector:

// Debug: Get all matching elements
var count = await Page.Locator("button").CountAsync();
Console.WriteLine($"Found {count} buttons");

// Use more specific selector
var button = Page.GetByRole(AriaRole.Button, new() { Name = "Submit" });

Issue: Flaky Tests

Solutions:

1. Use Expect assertions (built-in retries)
2. Avoid hardcoded waits
3. Use Page.WaitForLoadStateAsync(LoadState.NetworkIdle)
4. Make selectors more specific

---

Quick Reference

Base Classes

PageTest      // Single page per test (most common)
ContextTest   // Browser context, create own pages
BrowserTest   // Full browser control

Common Patterns

// Navigation
await Page.GotoAsync("url");

// Waiting
await Page.WaitForLoadStateAsync(LoadState.NetworkIdle);
await Page.WaitForSelectorAsync("button");

// Locators
Page.Locator("css")
Page.GetByTestId("id")
Page.GetByRole(AriaRole.Button)
Page.GetByText("text")

// Assertions
await Expect(Page).ToHaveTitleAsync("title");
await Expect(element).ToBeVisibleAsync();
await Expect(element).ToHaveTextAsync("text");

// Actions
await element.ClickAsync();
await element.FillAsync("value");
await element.CheckAsync();

Running Tests

# Run all Playwright tests
dotnet run --project tests/ClaudeStack.Web.Tests.Playwright

# Headed mode
$env:HEADED="1"
dotnet run --project tests/ClaudeStack.Web.Tests.Playwright

# Debug mode
$env:PWDEBUG="1"
dotnet run --project tests/ClaudeStack.Web.Tests.Playwright

Browser Installation

cd tests/ClaudeStack.Web.Tests.Playwright/bin/Debug/net10.0
./playwright.ps1 install              # All browsers
./playwright.ps1 install chromium     # Chromium only
./playwright.ps1 install --with-deps  # With system dependencies (Linux)

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Related Skills

• mstest-testing-platform: Running Playwright tests with Microsoft.Testing.Platform
• dotnet-centralized-packages: Managing Playwright package versions
• dotnet-cli-essentials: Building and running test projects

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Additional Resources

• Playwright .NET Documentation
• Microsoft.Playwright.MSTest.v4 Package
• Playwright API Reference
• Best Practices

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Version Information

• Microsoft.Playwright.MSTest.v4: 1.55.0-beta-4
• Playwright Version: 1.55 (beta)
• .NET SDK: 10.0.100-rc.2.25502.107

This skill is accurate as of Playwright 1.55 beta. Some APIs may change in future versions.