Testing & Performance in .NET

Master advanced testing strategies and performance optimization for .NET enterprise applications.

45 min•By Priygop Team•Last updated: Feb 2026

Testing Strategy

Unit Tests: Test domain logic and application handlers in isolation — use xUnit, NSubstitute/Moq. Aim for 80%+ coverage on Domain and Application layers
Integration Tests: Test database queries, API endpoints, and external service integration — use WebApplicationFactory and Testcontainers for realistic environments
Architecture Tests: Verify layer dependencies using NetArchTest — 'Domain should NOT reference Infrastructure'. Prevent accidental dependency violations
Contract Tests: Verify API contracts between services — Pact.NET ensures consumer and provider agree on request/response formats
Performance Tests: Load test APIs with k6 or NBomber — establish baselines and catch regressions before production
Mutation Testing: Stryker.NET modifies your code and checks if tests catch the mutations — reveals gaps in test quality beyond code coverage

Try It Yourself: C# Design Patterns

Try It Yourself: C# Design PatternsHTML⚠ 10 errors

⚠ Syntax Issues (10)

Line 43: Unknown tag <string> on line 43

💡 "<string>" is not a valid HTML5 element. Use <div>, <span>, <p>, <section>, etc.

Line 45: Unknown tag <string> on line 45

💡 "<string>" is not a valid HTML5 element. Use <div>, <span>, <p>, <section>, etc.

Line 57: Wrong closing tag: </script> found, expected </string> (line 57)

💡 Close <string> (opened on line 45) with </string> before closing </script>.

Line 57: Wrong closing tag: </body> found, expected </string> (line 57)

💡 Close <string> (opened on line 45) with </string> before closing </body>.

Line 57: Wrong closing tag: </html> found, expected </string> (line 57)

💡 Close <string> (opened on line 45) with </string> before closing </html>.

Line 2: Unclosed <html> (opened on line 2)

💡 Add </html> to properly close this element.

Line 9: Unclosed <body> (opened on line 9)

💡 Add </body> to properly close this element.

Line 16: Unclosed <script> (opened on line 16)

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Line 43: Unclosed <string> (opened on line 43)

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HTML Editor

✕ 10 errorsTab = 2 spaces

<!DOCTYPE html>
<html><head><style>
body{font-family:Arial,sans-serif;padding:20px;background:#1e1e2e;color:#cdd6f4}
h2{color:#89b4fa}.card{background:#313244;padding:20px;border-radius:10px;max-width:550px}
pre{background:#1e1e2e;padding:14px;border-radius:8px;font-size:13px;border:1px solid #45475a;overflow-x:auto;line-height:1.5}
.tabs{display:flex;gap:6px;flex-wrap:wrap;margin:12px 0}
.tab{padding:8px 14px;border-radius:6px;cursor:pointer;font-size:13px;font-weight:bold;background:#45475a;color:#bac2de;border:none}
.tab.active{background:#89b4fa;color:#1e1e2e}
</style></head><body>
<div class="card"><h2>C# Design Patterns</h2>
<div class="tabs">
<button class="tab active" onclick="show(0,this)">Singleton</button>
<button class="tab" onclick="show(1,this)">Factory</button>
<button class="tab" onclick="show(2,this)">Observer</button></div>
<pre id="code"></pre></div>
<script>
var codes=["// Singleton Pattern
public class Database {
    private static Database _instance;
    private Database() { }

    public static Database Instance =>
        _instance ??= new Database();

    public void Query(string sql)
        => Console.WriteLine(sql);
}","// Factory Pattern
public interface INotification {
    void Send(string msg);
}

public class EmailNotification : INotification {
    public void Send(string msg)
        => Console.WriteLine("Email: " + msg);
}

public static INotification Create(string type)
    => type switch {
        "email" => new EmailNotification(),
        _ => throw new ArgumentException()
    };","// Observer Pattern
public class EventBus {
    Dictionary<string list action string>>> _h = new();

    public void Subscribe(string e, Action<string> h) {
        if (!_h.ContainsKey(e)) _h[e] = new();
        _h[e].Add(h);
    }

    public void Publish(string e, string data) {
        if (_h.ContainsKey(e))
            _h[e].ForEach(h => h(data));
    }
}"];
function show(i,el){document.getElementById("code").textContent=codes[i];document.querySelectorAll(".tab").forEach(function(t){t.classList.remove("active");});el.classList.add("active");}
show(0,document.querySelector(".tab"));
</script></body></html>

<!DOCTYPE html>
<html><head><style>
body{font-family:Arial,sans-serif;padding:20px;background:#1e1e2e;color:#cdd6f4}
h2{color:#89b4fa}.card{background:#313244;padding:20px;border-radius:10px;max-width:550px}
pre{background:#1e1e2e;padding:14px;border-radius:8px;font-size:13px;border:1px solid #45475a;overflow-x:auto;line-height:1.5}
.tabs{display:flex;gap:6px;flex-wrap:wrap;margin:12px 0}
.tab{padding:8px 14px;border-radius:6px;cursor:pointer;font-size:13px;font-weight:bold;background:#45475a;color:#bac2de;border:none}
.tab.active{background:#89b4fa;color:#1e1e2e}
</style></head><body>
<div class="card"><h2>C# Design Patterns</h2>
<div class="tabs">
<button class="tab active" onclick="show(0,this)">Singleton</button>
<button class="tab" onclick="show(1,this)">Factory</button>
<button class="tab" onclick="show(2,this)">Observer</button></div>
<pre id="code"></pre></div>
<script>
var codes=["// Singleton Pattern
public class Database {
    private static Database _instance;
    private Database() { }

public static Database Instance =>
        _instance ??= new Database();

public void Query(string sql)
        => Console.WriteLine(sql);
}","// Factory Pattern
public interface INotification {
    void Send(string msg);
}

public class EmailNotification : INotification {
    public void Send(string msg)
        => Console.WriteLine("Email: " + msg);
}

public static INotification Create(string type)
    => type switch {
        "email" => new EmailNotification(),
        _ => throw new ArgumentException()
    };","// Observer Pattern
public class EventBus {
    Dictionary<string, List<Action<string>>> _h = new();

public void Subscribe(string e, Action<string> h) {
        if (!_h.ContainsKey(e)) _h[e] = new();
        _h[e].Add(h);
    }

public void Publish(string e, string data) {
        if (_h.ContainsKey(e))
            _h[e].ForEach(h => h(data));
    }
}"];
function show(i,el){document.getElementById("code").textContent=codes[i];document.querySelectorAll(".tab").forEach(function(t){t.classList.remove("active");});el.classList.add("active");}
show(0,document.querySelector(".tab"));
</script></body></html>

Result

Click ▶ Run to see the result

Edit the code on the left, then click Run

HTML|57 lines|2162 chars|10 errors, 0 warnings

UTF-8

Quick Quiz — .NET Architecture

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