test(mcp-test): await async GET stream in version-negotiation assertions

The GET /mcp stream is opened asynchronously once initialize creates the session, so asserting recorded calls immediately races under load (seen as Jackson 2 Integration Tests failing usesLatestVersion with Expected size: 3 but was: 2). Await the recorded GET before asserting header propagation.

Author: slachiewicz

mcp-test/src/test/java/io/modelcontextprotocol/common/HttpClientStreamableHttpVersionNegotiationIntegrationTests.java

@@ -4,6 +4,7 @@
 
 package io.modelcontextprotocol.common;
 
+import java.time.Duration;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -23,6 +24,7 @@
 import org.apache.catalina.LifecycleException;
 import org.apache.catalina.LifecycleState;
 import org.apache.catalina.startup.Tomcat;
+import static org.awaitility.Awaitility.await;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 
@@ -75,6 +77,12 @@ void usesLatestVersion() {
 		McpSchema.CallToolResult response = client
 			.callTool(McpSchema.CallToolRequest.builder("test-tool").arguments(Map.of()).build());
 
+		// The GET /mcp stream is opened asynchronously once the initialize response
+		// creates the session, so wait for it to be recorded before asserting.
+		await().atMost(Duration.ofSeconds(5))
+			.untilAsserted(() -> assertThat(requestRecordingFilter.getCalls()).filteredOn(c -> "GET".equals(c.method()))
+				.hasSize(1));
+
 		var calls = requestRecordingFilter.getCalls();
 
 		assertThat(calls).filteredOn(c -> !c.body().contains("\"method\":\"initialize\""))