Roadmap › 5. Automation & Industry 4.0 › Step 52

Test Automation — Selenium, Playwright, API and BDD with C#

Testing fundamentals and the test pyramid, NUnit/xUnit, Selenium WebDriver and locators, waits, Page Object Model, Playwright for .NET, API testing with HttpClient/RestSharp/Postman, BDD with Reqnroll (SpecFlow), data-driven tests, CI pipelines, flaky tests and the SDET interview questions.

What it is & where it is used

Test automation means writing code that tests software automatically and repeatably — UI tests that drive a browser, API tests that call endpoints, and unit/integration tests that check code directly. An SDET (Software Development Engineer in Test) or automation engineer builds and maintains these frameworks and runs them in CI/CD.

The test pyramid (Mike Cohn):

text

          /  UI / E2E  \        few — slow, brittle, test real user flows
         /  API / service \     more — fast, stable, test business rules through the API
        /    Unit tests     \   most — milliseconds, test classes/functions in isolation

Level	Tools (.NET)	Speed
Unit	xUnit, NUnit, MSTest + Moq/NSubstitute + FluentAssertions	ms
Integration	`WebApplicationFactory`, Testcontainers, EF Core with real SQL	seconds
API	HttpClient, RestSharp, Postman/Newman, Playwright API	seconds
UI / E2E	Selenium WebDriver, Playwright, Cypress (JS)	seconds–minutes
BDD	Reqnroll (successor of SpecFlow), Cucumber	wraps any level
Performance	k6, JMeter, NBomber, Azure Load Testing	minutes

Versions & history

Year	Milestone
2004	Selenium created at ThoughtWorks (Jason Huggins)
2011	Selenium 2 merges WebDriver
2016	Selenium 3 (Selenium RC removed)
2018	WebDriver becomes a W3C Recommendation
2020	Playwright released by Microsoft (Node), .NET/Python/Java bindings in 2021
2021	Selenium 4 — W3C protocol, relative locators, CDP access, new Grid
2023	Selenium Manager (automatic driver download) built in from 4.6+
2024	SpecFlow end-of-life announced; community fork Reqnroll becomes the .NET BDD standard; WebDriver BiDi rolling out
2025	Playwright 1.5x — test agents, MCP integration; Selenium 4.3x with BiDi APIs

Lifecycle

Automation in the software testing life cycle (STLC):

Requirement analysis — which acceptance criteria can be automated; risk-based selection.
Test planning — scope, tools, framework design, environments, data strategy.
Test design — test cases, data sets, page objects, API contracts.
Framework & scripts — build reusable framework, write tests, code review them like product code.
Execution — locally and in CI (on every PR: unit + API smoke; nightly: full regression; parallel/grid).
Reporting — results, screenshots, videos, traces (Allure, ExtentReports, Azure Test Plans, Playwright HTML report).
Maintenance — fix flaky tests, update locators, refactor; delete tests that no longer give value.

Tools used to develop

Test runners: NUnit, xUnit, MSTest; dotnet test.
UI: Selenium WebDriver (C#), Playwright for .NET (Microsoft.Playwright), Appium (mobile), WinAppDriver/FlaUI (Windows desktop).
API: HttpClient, RestSharp, Flurl, Postman + Newman, Playwright APIRequestContext.
BDD: Reqnroll (Gherkin .feature files with C# step definitions).
Assertions & mocks: FluentAssertions / Shouldly, Moq, NSubstitute, WireMock.Net (fake HTTP services).
Data & environments: Bogus (fake data), Testcontainers (Docker DBs), Selenium Grid / Selenoid, BrowserStack, Sauce Labs.
CI & reporting: Azure DevOps, GitHub Actions, Jenkins, Allure, ExtentReports.