feat: Add kotlin-sdk-testing module with channel-based transport implementation (#505)

# feat: Add kotlin-sdk-testing module with channel-based transport
implementation

- Introduced `kotlin-sdk-testing` module for testing utilities in the
MCP Kotlin SDK.
- Implemented `ChannelTransport`, providing JSON-RPC transport via
Kotlin coroutines channels.

<!-- Provide a brief summary of your changes -->

## Motivation and Context
This ChannelTransport can be used for testing Server implementation
without using real transports.

## How Has This Been Tested?
Unit test

## Breaking Changes
No

## Types of changes

- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [x] Documentation update

## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed

kotlin-sdk-client/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/client/AbstractClientTransportLifecycleTest.kt

@@ -4,7 +4,7 @@ import io.kotest.assertions.nondeterministic.eventually
 import io.kotest.assertions.throwables.shouldThrow
 import io.kotest.matchers.shouldBe
 import io.kotest.matchers.string.shouldContain
-import io.modelcontextprotocol.kotlin.sdk.shared.AbstractTransport
+import io.modelcontextprotocol.kotlin.sdk.shared.AbstractClientTransport
 import io.modelcontextprotocol.kotlin.sdk.types.McpException
 import io.modelcontextprotocol.kotlin.sdk.types.PingRequest
 import io.modelcontextprotocol.kotlin.sdk.types.RPCError.ErrorCode.CONNECTION_CLOSED
@@ -16,7 +16,7 @@ import kotlin.test.Test
 import kotlin.time.Duration.Companion.milliseconds
 import kotlin.time.Duration.Companion.seconds
 
-abstract class AbstractClientTransportLifecycleTest<T : AbstractTransport> {
+abstract class AbstractClientTransportLifecycleTest<T : AbstractClientTransport> {
 
     protected lateinit var transport: T
 

kotlin-sdk-client/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/client/channel/ChannelClientTransportLifecycleTest.kt

@@ -0,0 +1,20 @@
+package io.modelcontextprotocol.kotlin.sdk.client.channel
+
+import io.modelcontextprotocol.kotlin.sdk.ExperimentalMcpApi
+import io.modelcontextprotocol.kotlin.sdk.client.AbstractClientTransportLifecycleTest
+import io.modelcontextprotocol.kotlin.sdk.testing.ChannelTransport
+import kotlin.test.Ignore
+import kotlin.test.Test
+
+@OptIn(ExperimentalMcpApi::class)
+class ChannelClientTransportLifecycleTest : AbstractClientTransportLifecycleTest<ChannelTransport>() {
+
+    /**
+     * Dummy method to make IDE treat this class as a test
+     */
+    @Test
+    @Ignore
+    fun dummyTest() = Unit
+
+    override fun createTransport(): ChannelTransport = ChannelTransport()
+}