Bound STDIO client reads

Signed-off-by: Daniel Garnier-Moiroux <git@garnier.wf>

mcp-test/src/test/java/io/modelcontextprotocol/client/transport/StdioClientTransportTests.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2026-2026 the original author or authors.
+ */
+
+package io.modelcontextprotocol.client.transport;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.time.Duration;
+
+import org.awaitility.Awaitility;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import reactor.test.StepVerifier;
+
+import static io.modelcontextprotocol.util.McpJsonMapperUtils.JSON_MAPPER;
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Integration tests for {@link StdioClientTransport}.
+ *
+ * @author Daniel Garnier-Moiroux
+ */
+class StdioClientTransportTests {
+
+	private final PrintStream originalOut = System.out;
+
+	private final PrintStream originalErr = System.err;
+
+	private ByteArrayOutputStream testErr;
+
+	@BeforeEach
+	void setUp() {
+		testErr = new ByteArrayOutputStream();
+		PrintStream testOutPrintStream = new PrintStream(testErr, true);
+		System.setOut(testOutPrintStream);
+		System.setErr(testOutPrintStream);
+	}
+
+	@AfterEach
+	void tearDown() {
+		System.setOut(originalOut);
+		System.setErr(originalErr);
+	}
+
+	@Test
+	void shouldRejectInboundMessageExceedingMaxSize() throws Exception {
+		// A server process that emits an endless line with no newline terminator. A
+		// plain BufferedReader#readLine would buffer it all; the bounded reader must
+		// abort instead of exhausting memory.
+		int maxSize = 1024;
+		ServerParameters params = ServerParameters.builder("sh").args("-c", "while :; do printf a; done").build();
+
+		StdioClientTransport transport = new StdioClientTransport(params, JSON_MAPPER, maxSize);
+		try {
+			StepVerifier.create(transport.connect(msg -> msg)).verifyComplete();
+
+			Awaitility.await()
+				.atMost(Duration.ofSeconds(5))
+				.pollInterval(Duration.ofMillis(100))
+				.untilAsserted(() -> assertThat(testErr.toString())
+					.contains("Inbound message exceeds the maximum allowed size"));
+		}
+		finally {
+			StepVerifier.create(transport.closeGracefully()).verifyComplete();
+		}
+	}
+
+}