Add test coverage for Stdio server transport

Author: nquinquenel

src/test/java/org/sonarsource/sonarqube/mcp/transport/StdioServerTransportProviderTest.java

@@ -0,0 +1,127 @@
+/*
+ * SonarQube MCP Server
+ * Copyright (C) 2025 SonarSource
+ * mailto:info AT sonarsource DOT com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the Sonar Source-Available License Version 1, as published by SonarSource Sàrl.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the Sonar Source-Available License for more details.
+ *
+ * You should have received a copy of the Sonar Source-Available License
+ * along with this program; if not, see https://sonarsource.com/license/ssal/
+ */
+package org.sonarsource.sonarqube.mcp.transport;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import io.modelcontextprotocol.spec.McpServerSession;
+import java.time.Duration;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+import reactor.core.publisher.Mono;
+
+import static org.assertj.core.api.Assertions.assertThatCode;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+class StdioServerTransportProviderTest {
+
+  /**
+   * Helper to create a provider with a mock session without starting the internal transport.
+   * We need to use reflection to set the session field directly to avoid the background threads.
+   */
+  private StdioServerTransportProvider createProviderWithMockSession(McpServerSession mockSession) throws Exception {
+    var provider = new StdioServerTransportProvider(new ObjectMapper());
+    var sessionField = StdioServerTransportProvider.class.getDeclaredField("session");
+    sessionField.setAccessible(true);
+    sessionField.set(provider, mockSession);
+    return provider;
+  }
+
+  @Test
+  void closeGracefully_should_return_empty_mono_when_session_is_null() {
+    var provider = new StdioServerTransportProvider(new ObjectMapper());
+
+    var result = provider.closeGracefully();
+
+    assertThatCode(() -> result.block(Duration.ofSeconds(1))).doesNotThrowAnyException();
+  }
+
+  @Test
+  void closeGracefully_should_complete_successfully_when_session_closes_quickly() throws Exception {
+    var mockSession = mock(McpServerSession.class);
+    when(mockSession.closeGracefully()).thenReturn(Mono.empty());
+    var provider = createProviderWithMockSession(mockSession);
+
+    var result = provider.closeGracefully();
+
+    assertThatCode(() -> result.block(Duration.ofSeconds(2))).doesNotThrowAnyException();
+    verify(mockSession, times(1)).closeGracefully();
+    verify(mockSession, never()).close();
+  }
+
+  @Test
+  void closeGracefully_should_timeout_and_force_close_after_10_seconds() throws Exception {
+    var mockSession = mock(McpServerSession.class);
+    when(mockSession.closeGracefully()).thenReturn(Mono.never());
+    var provider = createProviderWithMockSession(mockSession);
+
+    var result = provider.closeGracefully();
+
+    assertThatCode(() -> result.block(Duration.ofSeconds(12))).doesNotThrowAnyException();
+    verify(mockSession, times(1)).closeGracefully();
+    verify(mockSession, times(1)).close(); // Should be force-closed
+  }
+
+  @Test
+  void closeGracefully_should_handle_error_and_complete_gracefully() throws Exception {
+    var mockSession = mock(McpServerSession.class);
+    when(mockSession.closeGracefully()).thenReturn(
+      Mono.error(new RuntimeException("Close failed"))
+    );
+    var provider = createProviderWithMockSession(mockSession);
+
+    var result = provider.closeGracefully();
+
+    assertThatCode(() -> result.block(Duration.ofSeconds(2))).doesNotThrowAnyException();
+    verify(mockSession, times(1)).closeGracefully();
+  }
+
+  @Test
+  void closeGracefully_should_handle_exception_during_forced_close() throws Exception {
+    var mockSession = mock(McpServerSession.class);
+    when(mockSession.closeGracefully()).thenReturn(Mono.never());
+    Mockito.doThrow(new RuntimeException("Force close failed"))
+      .when(mockSession).close();
+    var provider = createProviderWithMockSession(mockSession);
+
+    var result = provider.closeGracefully();
+
+    assertThatCode(() -> result.block(Duration.ofSeconds(12))).doesNotThrowAnyException();
+    verify(mockSession, times(1)).closeGracefully();
+    verify(mockSession, times(1)).close();
+  }
+
+  @Test
+  void closeGracefully_should_complete_immediately_if_session_closes_in_5_seconds() throws Exception {
+    var mockSession = mock(McpServerSession.class);
+    when(mockSession.closeGracefully()).thenReturn(
+      Mono.delay(Duration.ofSeconds(5)).then()
+    );
+    var provider = createProviderWithMockSession(mockSession);
+
+    var result = provider.closeGracefully();
+
+    assertThatCode(() -> result.block(Duration.ofSeconds(7))).doesNotThrowAnyException();
+    verify(mockSession, times(1)).closeGracefully();
+    verify(mockSession, never()).close();
+  }
+
+}
+