Update AGENTS.md with test writing guidelines.

Improve consistency and add details to AGENTS.md, including test-writing and best practices.

Author: kpavlov

AGENTS.md

@@ -3,6 +3,7 @@
 MCP Kotlin SDK — Kotlin Multiplatform implementation of the Model Context Protocol.
 
 ## Repository Layout
+
 - `kotlin-sdk-core`: Core protocol types, transport abstractions, WebSocket implementation
 - `kotlin-sdk-client`: Client transports (STDIO, SSE, StreamableHttp, WebSocket)
 - `kotlin-sdk-server`: Server transports + Ktor integration (STDIO, SSE, WebSocket)
@@ -11,13 +12,15 @@ MCP Kotlin SDK — Kotlin Multiplatform implementation of the Model Context Prot
 - `samples/`: Three sample projects (composite builds)
 
 ## General Guidance
+
 - Avoid changing public API signatures. Run `./gradlew apiCheck` before every commit.
 - **Explicit API mode** is strict: all public APIs must have explicit visibility modifiers and return types.
 - Anything under an `internal` directory is not part of the public API and may change freely.
 - Package structure follows: `io.modelcontextprotocol.kotlin.sdk.*`
 - The SDK targets Kotlin 2.2+ and JVM 1.8+ as minimum.
 
 ## Building and Testing
+
 1. Build the project:
    ```bash
    ./gradlew build
@@ -43,7 +46,17 @@ MCP Kotlin SDK — Kotlin Multiplatform implementation of the Model Context Prot
    ```
 
 ## Tests
-- All tests for each module are located in `src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/`
+
+- Write comprehensive tests for new features
+- **Prioritize test readability**
+- Avoid creating too many test methods. If multiple parameters can be tested in one scenario, go for it.
+- In case of similar scenarios/use-cases, consider using parametrized tests.
+  But never make a parametrized test for only one use-case
+- Use function `Names with backticks` for test methods in Kotlin, e.g. "fun `should return 200 OK`()"
+- Avoid writing KDocs for tests, keep code self-documenting
+- When running tests on a Kotlin Multiplatform project, run only JVM tests,
+  if not asked to run tests on another platform either.
+- Common tests for each module are located in `src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/`
 - Platform-specific tests go in `src/jvmTest/`, `src/jsTest/`, etc.
 - Use Kotest assertions (`shouldBe`, `shouldContain`, etc.) for readable test failures.
 - Use `shouldMatchJson` from Kotest for JSON validation.
@@ -53,41 +66,48 @@ MCP Kotlin SDK — Kotlin Multiplatform implementation of the Model Context Prot
 ## Code Conventions
 
 ### Multiplatform Patterns
+
 - Use `expect`/`actual` pattern for platform-specific implementations in `utils.*` files.
 - Test changes on JVM first, then verify platform-specific behavior if needed.
 - Supported targets: JVM (1.8+), JS/Wasm, iOS, watchOS, tvOS.
 
 ### Serialization
+
 - Use Kotlinx Serialization with explicit `@Serializable` annotations.
 - Custom serializers should be registered in the companion object.
 - JSON config is defined in `McpJson.kt` — use it consistently.
 
 ### Concurrency and State
+
 - Use `kotlinx.atomicfu` for thread-safe operations across platforms.
 - Prefer coroutines over callbacks where possible.
 - Transport implementations extend `AbstractTransport` for consistent callback management.
 
 ### Error Handling
+
 - Use sealed classes for representing different result states.
 - Map errors to JSON-RPC error codes in protocol handlers.
 - Log errors using `io.github.oshai.kotlinlogging.KotlinLogging`.
 
 ### Logging
+
 - Use `KotlinLogging.logger {}` for structured logging.
 - Never log sensitive data (credentials, tokens).
 
 ## Pull Requests
+
 - Base all PRs on the `main` branch.
 - PR title format: Brief description of the change
 - Include in PR description:
-  - **What changed?**
-  - **Why? Motivation and context**
-  - **Breaking changes?** (if any)
+    - **What changed?**
+    - **Why? Motivation and context**
+    - **Breaking changes?** (if any)
 - Run `./gradlew apiCheck` before submitting.
 - Link PR to related issue (except for minor docs/typo fixes).
 - Follow [Kotlin Coding Conventions](https://kotlinlang.org/docs/reference/coding-conventions.html).
 
 ## Review Checklist
+
 - `./gradlew apiCheck` must pass.
 - `./gradlew test` must succeed for affected modules.
 - New tests added for any new feature or bug fix.