210 lines
12 KiB
Markdown
210 lines
12 KiB
Markdown
---
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description: C# naming, layout, and primary constructors; Microsoft conventions and .NET idioms.
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globs: "**/*.cs"
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alwaysApply: true
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---
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# C# style (Neon Sprawl)
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Follow Microsoft’s **[C# Coding Conventions](https://learn.microsoft.com/en-us/dotnet/csharp/fundamentals/coding-style/coding-conventions)** and **[C# identifier rules](https://learn.microsoft.com/en-us/dotnet/csharp/fundamentals/coding-style/identifier-names)**. Prefer clarity and consistency with existing server code.
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## Naming
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- **Types** (classes, structs, records, interfaces, enums, delegates): `PascalCase`.
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- **Interfaces:** prefix with `I` (e.g. `IPlayerSession`).
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- **Methods, properties, events, public fields:** `PascalCase`.
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- **Parameters, local variables:** `camelCase`.
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- **Private instance fields:** `camelCase` (no leading underscore), unless an existing file consistently does otherwise—then match the file. If a parameter or local shadows a field, use `this.` or rename for clarity.
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- **Static fields:** `camelCase` for private/internal static fields; `PascalCase` for `public static` members (including `readonly`/constants) per Microsoft guidance; stay consistent within a project.
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- **Async methods:** suffix with `Async` (e.g. `LoadProfileAsync`).
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## Primary constructors
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- Prefer **primary constructor** syntax for classes, structs, and records when it fits: dependency injection, `IClassFixture<>` test classes, small services, and any type that mainly captures parameters into fields or base calls.
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- **Skip** primary constructors when they hurt clarity: heavy logic in the body that belongs in a conventional constructor, `this` references before the implicit constructor runs in odd ways, or a file already uses a consistent legacy style—then match the file.
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```csharp
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// Prefer
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public sealed class OrderService(IOrderStore store, ILogger<OrderService> log)
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{
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public Task<Order?> GetAsync(Guid id) => store.FindAsync(id);
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}
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// Avoid when you would only reassign into mutable fields with non-trivial validation—use an explicit constructor instead.
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```
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## Layout and syntax
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- **Braces:** opening brace `{` on a **new line** for types and members (Allman-style), per common Microsoft examples.
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- **Braces for every block:** never omit `{ }` on `if`, `else`, `for`, `foreach`, `while`, `do`, or `using` when the language allows a single statement without braces—**always** use a braced block, even for one line. This avoids accidental logic changes when editing. Expression-bodied members and expression lambdas (`x => x.Id`) stay valid when the whole body is a single expression.
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```csharp
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// Prefer
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if (string.IsNullOrEmpty(key))
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{
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return false;
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}
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// Avoid
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if (string.IsNullOrEmpty(key))
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return false;
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```
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- **Indentation:** **4 spaces** per level; no tabs unless the file already uses tabs—never mix.
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- **`var`:** use when the type is obvious from the right-hand side; use explicit types when it improves readability or for literals where the type matters.
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- **File-scoped namespaces** (`namespace X;`) for new single-namespace files when the SDK/version allows.
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- **Pattern matching / nullability:** prefer modern C# features where they simplify code; honor **nullable reference type** annotations when the project enables them.
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## Collection expressions (IDE0305)
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- Prefer **collection spread** (`[.. source]`) over **`.ToArray()`** / **`.ToList()`** when materializing a sequence into a new array or list for return values, record `with` copies, or local snapshots.
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- Give an **explicit target type** when the compiler cannot infer one (CS9176), e.g. `string[] ids = [.. query.Select(static x => x.Id)];`.
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- In **assertions**, avoid passing a bare spread directly to APIs with span overloads (e.g. `Assert.Equal`) — assign to a typed local first:
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```csharp
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// Prefer
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return [.. query];
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GrantedItems = [.. row.GrantedItems],
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// When type inference fails
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string[] expectedOrder = [.. registry.GetDefinitionsInIdOrder().Select(static d => d.Id)];
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string[] actualOrder = [.. body.Quests.Select(static row => row.QuestId)];
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Assert.Equal(expectedOrder, actualOrder);
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// Avoid (ambiguous Assert overloads; unnecessary allocation helper)
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Assert.Equal(expectedOrder, [.. body.Quests.Select(static row => row.QuestId)]);
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return query.ToArray();
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```
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## `using` / `await using` (IDE0063)
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- When a **`using` or `await using` block contains exactly one statement**, prefer the declaration form without braces: `await using var conn = …;` then the single statement on following lines **only if** it is still logically one resource scope (typical for `NpgsqlConnection` + one command in integration-test reset helpers).
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- **Keep braced `using (var …) { … }`** when the block has **multiple statements** (Arrange + Act + Assert inside one scope, seed loops, or any sequence that shares locals).
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- **Do not flatten** multi-statement blocks into `using var` at method scope when inner scopes reuse names like `store`, `registry`, or `scope` — that causes **CS0136** name clashes. Use distinct names (`seedStore`, `actScope`, `readStore`) or keep the braced block.
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## Local `const` (RCS1118)
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- When a local is initialized from a **compile-time constant** (string literal, numeric literal, or `public const` field), declare it **`const`** instead of **`var`**.
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```csharp
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const string questId = PrototypeE7M1QuestCatalogRules.GatherIntroQuestId;
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```
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## Inline declarations (IDE0018)
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- Prefer **inline initialization** over declare-then-assign when the analyzer suggests it, e.g. `var outcome = Operation(...)` and `TryGet(..., out var snapshot)` instead of separate upfront declarations.
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```csharp
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// Prefer — single disposable, single follow-on statement
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await using var conn = new NpgsqlConnection(cs);
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await conn.OpenAsync();
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// Prefer — multiple statements in one scope
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using (var firstScope = Factory.Services.CreateScope())
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{
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var store = firstScope.ServiceProvider.GetRequiredService<IExampleStore>();
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Assert.True(store.TryAppend(row));
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}
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// Avoid — flattens to method scope and collides with a later `var store`
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using var firstScope = Factory.Services.CreateScope();
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var store = firstScope.ServiceProvider.GetRequiredService<IExampleStore>();
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Assert.True(store.TryAppend(row));
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// … later …
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var store = secondScope.ServiceProvider.GetRequiredService<IExampleStore>(); // CS0136
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```
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## Postgres schema gates (IDE0330)
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- In `*Bootstrap.cs` types, use **`System.Threading.Lock`** (not `object`) for static schema-initialization gates: `private static readonly Lock SchemaGate = new();`.
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## Concrete return types (CA1859)
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- When a private helper always returns a materialized array, prefer the **concrete array type** as the return type (e.g. `RewardItemGrantApplied[]`) instead of `IReadOnlyList<T>` if callers only need the array and analyzers suggest it.
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- Prefer **expression-bodied** members only when they stay one clear idea.
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- **LINQ:** favor readability over micro-chains; break complex queries across lines.
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- **Exception handling:** catch specific exceptions; avoid empty `catch`; log or rethrow with context when appropriate.
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## `Program.cs` and minimal APIs
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- Top-level statements and minimal APIs are fine for small apps; extract registration/build logic into extension methods or dedicated types when the file grows.
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## Documentation
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- Use **`///` XML doc comments** on public APIs (types and members) when behavior or contracts are not obvious.
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- **Primary-constructor records:** include a **`<summary>`** on the type. Prefer **`<see cref="PropertyName"/>`** in the summary for positional parameters. Do **not** use **`<param>`** on **`record struct`** primary constructors — Roslynator reports false-positive **RCS1263** ([roslynator#1730](https://github.com/dotnet/roslynator/issues/1730)). **`record class`** / **`class`** primary constructors may use `<param>` when the analyzer accepts them.
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## Null checks (IDE0270)
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- Prefer **`?? throw`** over `if (x is null) { throw … }` when assigning a non-null local from a nullable expression.
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```csharp
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var root = FindDockerComposeRoot()
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?? throw new InvalidOperationException("…");
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```
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## Test project layout (`*.Tests`)
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- **Mirror the server project:** place test types under the same relative path as the production code they exercise (e.g. `NeonSprawl.Server/Game/PositionState/PositionStateApi.cs` → `NeonSprawl.Server.Tests/Game/PositionState/PositionStateApiTests.cs`).
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- Use a namespace that matches the folder tree under the test assembly root, e.g. `NeonSprawl.Server.Tests.Game.PositionState` for files in `Game/PositionState/`.
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## Test method naming convention
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- Use **`MethodName_ShouldExpectedOutcome_WhenScenario`** (three segments, **`PascalCase`** inside each segment, separated by **underscores**).
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- **`MethodName`:** the behavior or entry under test (SUT method, HTTP operation, or short feature verb)—e.g. `GetPosition`, `PostMove`, `TryApplyMoveTarget`.
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- **`ShouldExpectedOutcome`:** the outcome the test proves—e.g. `ShouldReturnNotFound`, `ShouldPersistTargetAndIncrementSequence`.
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- **`WhenScenario`:** the condition or inputs that trigger it—e.g. `WhenPlayerIsUnknown`, `WhenDevPlayerPostsValidMove`.
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- Omit redundant words when the scenario is already obvious; keep names readable in test runners and failure output.
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```csharp
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// Examples
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public async Task GetPosition_ShouldReturnNotFound_WhenPlayerIsUnknown() { … }
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public async Task PostMove_ShouldReturnBadRequest_WhenSchemaVersionIsWrong() { … }
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```
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## Unit and integration tests (Arrange, Act, Assert)
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**Mandatory for every new or changed test method** in `*Tests.cs` (`[Fact]` / `[Theory]` bodies). Do not ship partial AAA (e.g. comments present but body read still in Act). Agents and humans must treat this as **merge-ready** layout, not a suggestion.
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### Required layout
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1. **Phase labels** — Each test method contains **`// Arrange`**, **`// Act`**, and **`// Assert`** exactly once, in that order, each on its own line (same indentation as the test body). Use these exact words so grep and review stay consistent. **No blank line is required** immediately after those comments; the first statement of each phase may follow on the next line.
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2. **Arrange** — Factories, `HttpClient`, queued mock transports, DTOs, seeds, and other setup. Do **not** assert the **outcome under test** in Arrange (rare guards on arrange-only helpers are acceptable).
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3. **Act** — Invoke the **behavior under test** only (e.g. one `PostAsJsonAsync`, `GetAsync`, or SUT call). If the scenario *is* a short sequence (e.g. POST then GET to prove persistence), keep the whole sequence in Act with **no** `Assert.*` between those calls.
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4. **Assert** — All `Assert.*` (and any other outcome checks). **HTTP / deserialization:** when the next step is verifying the response (status already observed, body for assertions), perform **`ReadFromJsonAsync`** / similar **reads here**, not in Act beside the POST. Reads that **drive** the next call belong in Act, not Assert.
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5. **One AAA triple per test method** — Each `[Fact]` or `[Theory]` case gets its own Arrange/Act/Assert; do not share a single Assert block across unrelated scenarios in one method.
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### Authoring defaults
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- Use VS Code snippet **`xut`** (method) or **`xutc`** (class) from `.vscode/csharp.code-snippets`, or copy **`server/NeonSprawl.Server.Tests/TestTemplates/AAA_TEST_METHOD_TEMPLATE.cs.txt`**.
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### Example (minimal HTTP integration)
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```csharp
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[Fact]
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public async Task PostExample_ShouldReturnOk_WhenBodyValid()
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{
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// Arrange
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await using var factory = new InMemoryWebApplicationFactory();
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var client = factory.CreateClient();
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var request = new { schemaVersion = 1 };
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// Act
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var response = await client.PostAsJsonAsync("/game/example", request);
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// Assert
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var body = await response.Content.ReadFromJsonAsync<ExampleResponse>();
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Assert.Equal(HttpStatusCode.OK, response.StatusCode);
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Assert.NotNull(body);
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}
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```
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## Tooling
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- Prefer fixes that satisfy built-in **.NET analyzers** / `dotnet format` (if adopted) rather than fighting IDE warnings without reason.
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