SSE: Unit test for DataLeadStream

media/sse/src/main/java/org/glassfish/jersey/media/sse/OutboundEventWriter.java

@@ -129,7 +129,7 @@ public void writeTo(final OutboundSseEvent outboundEvent,
         }
     }
 
-    private static final class DataLeadStream extends OutputStream {
+    static final class DataLeadStream extends OutputStream {
         private final OutputStream entityStream;
 
         private int lastChar = -1;

media/sse/src/test/java/org/glassfish/jersey/media/sse/DataLeadStreamTest.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright (c) 2025 Markus KARG
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0, which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * This Source Code may also be made available under the following Secondary
+ * Licenses when the conditions for such availability set forth in the
+ * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
+ * version 2 with the GNU Classpath Exception, which is available at
+ * https://www.gnu.org/software/classpath/license.html.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+ */
+
+package org.glassfish.jersey.media.sse;
+
+import java.io.ByteArrayOutputStream;
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * Basic set of unit tests for {@link DataLeadStream}.
+ *
+ * @author Markus KARG (markus@headcrashing.eu)
+ */
+public class DataLeadStreamTest {
+
+    @Test
+    public void shouldDetectEolOnWrite() throws Exception {
+        // given
+        final var outputStream = new ByteArrayOutputStream();
+        final var dataLeadStream = new OutboundEventWriter.DataLeadStream(outputStream);
+
+        // when
+        dataLeadStream.write('A');
+        dataLeadStream.write('\r');
+        dataLeadStream.write('B');
+        dataLeadStream.write('\n');
+        dataLeadStream.write('C');
+        dataLeadStream.write('\r');
+        dataLeadStream.write('\n');
+        dataLeadStream.write('D');
+        dataLeadStream.write('\r');
+        dataLeadStream.write('\r');
+        dataLeadStream.write('E');
+        dataLeadStream.write('\n');
+        dataLeadStream.write('\n');
+        dataLeadStream.write('F');
+        dataLeadStream.write('\r');
+        dataLeadStream.write('\n');
+        dataLeadStream.write('\r');
+        dataLeadStream.write('\n');
+        dataLeadStream.write('G');
+        dataLeadStream.write("H".getBytes(UTF_8));
+        dataLeadStream.write("IJ".getBytes(UTF_8));
+        dataLeadStream.write("KLM".getBytes(UTF_8));
+        dataLeadStream.write("N\rO\nP\r\nQ\n\nR\r\rS\r\n\r\nT".getBytes(UTF_8));
+        dataLeadStream.write('\r');
+        dataLeadStream.write("U".getBytes(UTF_8));
+        dataLeadStream.write('\r');
+        dataLeadStream.write("\nV".getBytes(UTF_8));
+        dataLeadStream.write('\r');
+        dataLeadStream.write("\rW".getBytes(UTF_8));
+        dataLeadStream.write('\n');
+        dataLeadStream.write("X".getBytes(UTF_8));
+        dataLeadStream.write('\n');
+        dataLeadStream.write("\nY".getBytes(UTF_8));
+        dataLeadStream.write('\n');
+        dataLeadStream.write("\rZ".getBytes(UTF_8));
+        dataLeadStream.write("a\r".getBytes(UTF_8));
+        dataLeadStream.write('b');
+        dataLeadStream.write("c\n".getBytes(UTF_8));
+        dataLeadStream.write('d');
+        dataLeadStream.write("e\r".getBytes(UTF_8));
+        dataLeadStream.write('\r');
+        dataLeadStream.write("f\n".getBytes(UTF_8));
+        dataLeadStream.write('\n');
+        dataLeadStream.write("g\r".getBytes(UTF_8));
+        dataLeadStream.write('\n');
+        dataLeadStream.write("h\n".getBytes(UTF_8));
+        dataLeadStream.write('\r');
+        dataLeadStream.finish();
+
+        // then
+        assertEquals(
+                "data: A\ndata: B\ndata: C\ndata: D\ndata: \ndata: E\ndata: \ndata: F\ndata: \ndata: G"
+              + "H"
+              + "IJ"
+              + "KLM"
+              + "N\ndata: O\ndata: P\ndata: Q\ndata: \ndata: R\ndata: \ndata: S\ndata: \ndata: T"
+              + "\ndata: U"
+              + "\ndata: V"
+              + "\ndata: \ndata: W"
+              + "\ndata: X"
+              + "\ndata: \ndata: Y"
+              + "\ndata: \ndata: Z"
+              + "a\ndata: b"
+              + "c\ndata: d"
+              + "e\ndata: \ndata: "
+              + "f\ndata: \ndata: "
+              + "g\ndata: "
+              + "h\ndata: \ndata: ",
+                outputStream.toString(UTF_8));
+    }
+}