{"slug": "fastest-way-to-understand-stryker", "title": "Fastest Way to Understand Stryker", "summary": "The article provides a step-by-step guide to setting up a .NET solution with a console app, class library, and xUnit test project, then demonstrates how to install and run the Stryker mutation testing tool. It shows how Stryker introduces code mutations (e.g., changing `a + b` to `a - b`) and identifies whether tests fail, revealing weak tests that pass but don't properly verify behavior. The article concludes by noting that mature engineering teams integrate Stryker into CI/CD pipelines (e.g., GitHub Actions) to enforce high mutation scores.", "body_md": "## FASTEST WAY TO UNDERSTAND STRYKER\n\nWe'll create:\n\n```\nConsole App\n   ↓\nClass Library\n   ↓\nUnit Test Project\n   ↓\nRun Stryker\n```\n\nYou’ll understand:\n\n- solution structure\n- testing flow\n- mutation testing\n- enterprise-level quality tooling\n\n### STEP 1 - Create Solution\n\nOpen terminal:\n\n```\nmkdir StrykerDemo\ncd StrykerDemo\n\ndotnet new sln\n```\n\n### STEP 2 - Create Class Library\n\nThis contains business logic.\n\n```\ndotnet new classlib -n StrykerDemo.Core\n```\n\nAdd to solution:\n\n```\ndotnet sln add StrykerDemo.Core\n```\n\n### STEP 3 - Create Test Project\n\nUse xUnit.\n\n```\ndotnet new xunit -n StrykerDemo.Tests\n```\n\nAdd to solution:\n\n```\ndotnet sln add StrykerDemo.Tests\n```\n\nReference Core project:\n\n```\ndotnet add StrykerDemo.Tests reference StrykerDemo.Core\n```\n\n### STEP 4 - Create Actual Logic\n\nInside:\n\n```\nStrykerDemo.Core\n```\n\nCreate:\n\n```\nnamespace StrykerDemo.Core;\n\npublic class Calculator\n{\n    public int Add(int a, int b)\n    {\n        return a + b;\n    }\n}\n```\n\n### STEP 5 - Create Unit Test\n\nInside test project:\n\n```\nusing StrykerDemo.Core;\n\nnamespace StrykerDemo.Tests;\n\npublic class CalculatorTests\n{\n    [Fact]\n    public void Add_Should_Return_Correct_Value()\n    {\n        var calculator = new Calculator();\n\n        var result = calculator.Add(2, 3);\n\n        Assert.Equal(5, result);\n    }\n}\n```\n\n### STEP 6 - Verify Tests\n\nRun:\n\n```\ndotnet test\n```\n\nYou should see:\n\n```\nPassed!\n```\n\n### STEP 7 - Install Stryker\n\nInstall globally:\n\n```\ndotnet tool install -g dotnet-stryker\n```\n\nVerify:\n\n```\ndotnet stryker --version\n```\n\n### STEP 8 — RUN STRYKER\n\nGo to test project:\n\n```\ncd StrykerDemo.Tests\n```\n\nRun:\n\n```\ndotnet stryker\n```\n\n### WHAT HAPPENS NOW\n\nStryker will:\n\n- Find your code\n- Mutate it\n- Run tests repeatedly\n\nExample mutation:\n\nOriginal:\n\n```\na + b\n```\n\nMutated:\n\n```\na - b\n```\n\nYour test expects:\n\n```\n5\n```\n\nMutated result:\n\n```\n-1\n```\n\nTest fails.\n\nMutation killed ✅\n\n### NOW LET’S SEE A SURVIVING MUTATION\n\nChange test to weak test:\n\n```\nAssert.True(result > 0);\n```\n\ninstead of:\n\n```\nAssert.Equal(5, result);\n```\n\nNow rerun Stryker.\n\nSome mutations may survive because:\n\n- subtraction may still return positive\n- your assertion is too generic\n\nTHIS is where mutation testing becomes powerful.\n\n### Viewing the Stryker HTML Report\n\nAfter running:\n\n```\ndotnet stryker\n```\n\nStryker automatically generates an HTML report inside:\n\n```\nStrykerOutput/<timestamp>/reports/mutation-report.html\n```\n\nExample:\n\n```\nStrykerOutput/2026-05-23.14-56-48/reports/mutation-report.html\n```\n\nYou can also automatically open the report in your browser:\n\n```\ndotnet stryker --open-report\n```\n\nor\n\n```\ndotnet stryker -o\n```\n\n### THE BIG ENTERPRISE INSIGHT\n\nIn real enterprise systems:\n\n- code coverage can say 90%\n- but mutation score may say 40%\n\nMeaning:\n\ntests execute code but don’t truly verify behavior.\n\nThat’s why mature engineering teams use:\n\n- unit tests\n- integration tests\n- mutation testing\n- quality gates in CI/CD\n\n### HOW THIS LOOKS IN GITHUB\n\nUsually:\n\n```\nGitHub Actions\n    ↓\ndotnet test\n    ↓\ndotnet stryker\n    ↓\nFail pipeline if mutation score low\n```\n\nThis is where you begin seeing:\n\n- real engineering ownership\n- architecture visibility\n- DevOps quality flow\n- not just user story implementation\n\n### WHAT YOU SHOULD DO NEXT\n\nAfter this basic example:\n\n- Add more methods\n- Add edge cases\n- Purposely create weak tests\n- Watch mutations survive\n- Improve tests\n- Re-run Stryker That loop teaches more than tutorials.", "url": "https://wpnews.pro/news/fastest-way-to-understand-stryker", "canonical_source": "https://dev.to/davinceleecode/fastest-way-to-understand-stryker-2hd0", "published_at": "2026-05-22 14:57:01+00:00", "updated_at": "2026-05-22 15:03:07.518719+00:00", "lang": "en", "topics": ["developer-tools"], "entities": ["Stryker", "xUnit", "Calculator", "StrykerDemo.Core", "StrykerDemo.Tests"], "alternates": {"html": "https://wpnews.pro/news/fastest-way-to-understand-stryker", "markdown": "https://wpnews.pro/news/fastest-way-to-understand-stryker.md", "text": "https://wpnews.pro/news/fastest-way-to-understand-stryker.txt", "jsonld": "https://wpnews.pro/news/fastest-way-to-understand-stryker.jsonld"}}