C# MAUI Chaos Engineering — ทดสอบความทนทานของแอป

MAUI Chaos Engineering

C# MAUI Chaos Engineering Fault Injection Network Simulation UI Resilience Error Handling Polly Retry Circuit Breaker Production

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Chaos Scenario	Simulation	Expected Behavior	Test On
Network Timeout	Delay response 30+ sec	Timeout message, retry button	All platforms
Server Error (500)	Return HTTP 500	Error message, auto retry	All platforms
Auth Expired (401)	Return HTTP 401	Redirect to login, refresh token	All platforms
Offline	No internet	Offline banner, cached data	Android, iOS
Slow Network	3-5 sec delay	Loading indicator, no freeze	All platforms
Memory Pressure	Large data load	No crash, graceful degradation	Android, iOS

Fault Injection Setup

# === C# MAUI Chaos Engineering Setup ===



# // IChaosService.cs — Interface for chaos injection

# public interface IApiService

# {

#     Task<List<Item>> GetItemsAsync();

#     Task<Item> GetItemAsync(int id);

#     Task<bool> SaveItemAsync(Item item);

# }

#

# // ChaosApiService.cs — Chaos implementation

# public class ChaosApiService : IApiService

# {

#     private readonly IApiService _realService;

#     private readonly Random _random = new();

#     private readonly double _failureRate;

#

#     public ChaosApiService(IApiService realService, double failureRate = 0.3)

#     {

#         _realService = realService;

#         _failureRate = failureRate;

#     }

#

#     public async Task<List<Item>> GetItemsAsync()

#     {

#         await SimulateChaos();

#         return await _realService.GetItemsAsync();

#     }

#

#     private async Task SimulateChaos()

#     {

#         if (_random.NextDouble() < _failureRate)

#         {

#             var scenario = _random.Next(4);

#             switch (scenario)

#             {

#                 case 0: throw new HttpRequestException("Network error");

#                 case 1: throw new TimeoutException("Request timeout");

#                 case 2: await Task.Delay(5000); break; // Slow response

#                 case 3: throw new UnauthorizedAccessException("Token expired");

#             }

#         }

#     }

# }

#

# // MauiProgram.cs — DI Registration

# #if DEBUG

# builder.Services.AddSingleton<IApiService>(sp =>

#     new ChaosApiService(new RealApiService(sp.GetRequiredService<HttpClient>()), 0.3));

# #else

# builder.Services.AddSingleton<IApiService, RealApiService>();

# #endif



from dataclasses import dataclass



@dataclass

class ChaosScenario:

    scenario: str

    exception: str

    frequency: str

    user_impact: str

    handling: str



scenarios = [

    ChaosScenario("Network Error",

        "HttpRequestException", "30% of requests",

        "Cannot load data, shows error",

        "Retry 3x with backoff, show cached data"),

    ChaosScenario("Timeout",

        "TimeoutException / TaskCanceledException", "20% of requests",

        "Long wait, then error",

        "30s timeout, cancel task, show retry button"),

    ChaosScenario("Auth Expired",

        "UnauthorizedAccessException / HTTP 401", "10% of requests",

        "Redirected to login",

        "Refresh token automatically, retry once"),

    ChaosScenario("Server Error",

        "HttpRequestException (500)", "15% of requests",

        "Feature unavailable",

        "Circuit breaker, show maintenance message"),

    ChaosScenario("Slow Response",

        "Task.Delay(3000-5000)", "25% of requests",

        "Loading feels slow",

        "Show skeleton UI, progress indicator"),

]



print("=== Chaos Scenarios ===")

for s in scenarios:

    print(f"  [{s.scenario}] Exception: {s.exception}")

    print(f"    Frequency: {s.frequency} | Impact: {s.user_impact}")

    print(f"    Handling: {s.handling}")

Polly Resilience

# === Polly Configuration ===



# // Polly setup in MauiProgram.cs

# builder.Services.AddHttpClient("api", client =>

# {

#     client.BaseAddress = new Uri("https://api.example.com");

#     client.Timeout = TimeSpan.FromSeconds(30);

# })

# .AddPolicyHandler(GetRetryPolicy())

# .AddPolicyHandler(GetCircuitBreakerPolicy())

# .AddPolicyHandler(Policy.TimeoutAsync<HttpResponseMessage>(10));

#

# static IAsyncPolicy<HttpResponseMessage> GetRetryPolicy()

# {

#     return HttpPolicyExtensions

#         .HandleTransientHttpError()

#         .Or<TimeoutRejectedException>()

#         .WaitAndRetryAsync(3, retryAttempt =>

#             TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)),

#             onRetry: (outcome, timespan, retryAttempt, context) =>

#             {

#                 Debug.WriteLine($"Retry {retryAttempt} after {timespan.TotalSeconds}s");

#             });

# }

#

# static IAsyncPolicy<HttpResponseMessage> GetCircuitBreakerPolicy()

# {

#     return HttpPolicyExtensions

#         .HandleTransientHttpError()

#         .CircuitBreakerAsync(5, TimeSpan.FromSeconds(30),

#             onBreak: (result, duration) =>

#                 Debug.WriteLine($"Circuit OPEN for {duration.TotalSeconds}s"),

#             onReset: () => Debug.WriteLine("Circuit CLOSED"));

# }



@dataclass

class PollyPolicy:

    policy: str

    config: str

    when: str

    behavior: str



policies = [

    PollyPolicy("Retry",

        "3 retries, exponential backoff (2s, 4s, 8s)",

        "Transient HTTP errors (5xx, timeout)",

        "Auto retry, user sees loading longer"),

    PollyPolicy("Circuit Breaker",

        "Open after 5 failures, 30s cooldown",

        "Consecutive failures to same endpoint",

        "Fast fail, no wasted requests, show fallback"),

    PollyPolicy("Timeout",

        "10s per request, 30s overall",

        "Slow API responses",

        "Cancel request, show timeout message"),

    PollyPolicy("Fallback",

        "Return cached data on failure",

        "After all retries exhausted",

        "Show stale data with 'offline' indicator"),

    PollyPolicy("Bulkhead",

        "Max 10 concurrent requests",

        "Prevent resource exhaustion",

        "Queue excess requests, prevent app freeze"),

]



print("=== Polly Policies ===")

for p in policies:

    print(f"  [{p.policy}] Config: {p.config}")

    print(f"    When: {p.when}")

    print(f"    Behavior: {p.behavior}")

UI Resilience Testing

# === UI Testing Checklist ===



@dataclass

class UITest:

    test: str

    scenario: str

    expected: str

    platform: str

    automated: bool



ui_tests = [

    UITest("Loading State", "API call in progress",

        "Skeleton UI or spinner visible, no blank screen",

        "All", True),

    UITest("Error State", "API returns 500",

        "Error message with retry button, no crash",

        "All", True),

    UITest("Offline Banner", "No internet connection",

        "Banner shows 'Offline', cached data displayed",

        "Android, iOS", True),

    UITest("Timeout Recovery", "API timeout then succeeds",

        "Shows timeout, auto retry succeeds, UI updates",

        "All", True),

    UITest("Auth Redirect", "Token expired (401)",

        "Redirect to login, after login return to same page",

        "All", True),

    UITest("Pull to Refresh", "Stale data after error",

        "Pull down refreshes data, loading indicator shows",

        "Android, iOS", True),

    UITest("Back Navigation", "Error on current page",

        "Back button works, no stuck state",

        "All", True),

    UITest("Memory Pressure", "Load 10000 items in list",

        "CollectionView virtualizes, no OOM crash",

        "Android, iOS", False),

]



print("=== UI Resilience Tests ===")

for t in ui_tests:

    auto = "Automated" if t.automated else "Manual"

    print(f"  [{t.test}] {auto} | Platform: {t.platform}")

    print(f"    Scenario: {t.scenario}")

    print(f"    Expected: {t.expected}")