Add tests for SearchPipelineInfo

Signed-off-by: Michael Froh <froh@amazon.com>

server/src/test/java/org/opensearch/search/pipeline/SearchPipelineInfoTests.java

@@ -0,0 +1,75 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.search.pipeline;
+
+import org.opensearch.Version;
+import org.opensearch.common.io.stream.BytesStreamOutput;
+import org.opensearch.common.io.stream.StreamInput;
+import org.opensearch.test.OpenSearchTestCase;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+
+public class SearchPipelineInfoTests extends OpenSearchTestCase {
+    public void testSerializationRoundtrip() throws IOException {
+        SearchPipelineInfo searchPipelineInfo = new SearchPipelineInfo(
+            Map.of(
+                "a",
+                List.of(new ProcessorInfo("a1"), new ProcessorInfo("a2"), new ProcessorInfo("a3")),
+                "b",
+                List.of(new ProcessorInfo("b1"), new ProcessorInfo("b2")),
+                "c",
+                List.of(new ProcessorInfo("c1"))
+            )
+        );
+        SearchPipelineInfo deserialized;
+        try (BytesStreamOutput bytesStreamOutput = new BytesStreamOutput()) {
+            searchPipelineInfo.writeTo(bytesStreamOutput);
+            try (StreamInput bytesStreamInput = bytesStreamOutput.bytes().streamInput()) {
+                deserialized = new SearchPipelineInfo(bytesStreamInput);
+            }
+        }
+        assertTrue(deserialized.containsProcessor("a", "a1"));
+        assertTrue(deserialized.containsProcessor("a", "a2"));
+        assertTrue(deserialized.containsProcessor("a", "a3"));
+        assertTrue(deserialized.containsProcessor("b", "b1"));
+        assertTrue(deserialized.containsProcessor("b", "b2"));
+        assertTrue(deserialized.containsProcessor("c", "c1"));
+    }
+
+    /**
+     * When serializing / deserializing to / from old versions, processor type info is lost.
+     *
+     * Also, we only supported request/response processors.
+     */
+    public void testSerializationRoundtripBackcompat() throws IOException {
+        SearchPipelineInfo searchPipelineInfo = new SearchPipelineInfo(
+            Map.of(
+                Pipeline.REQUEST_PROCESSORS_KEY,
+                List.of(new ProcessorInfo("a1"), new ProcessorInfo("a2"), new ProcessorInfo("a3")),
+                Pipeline.RESPONSE_PROCESSORS_KEY,
+                List.of(new ProcessorInfo("b1"), new ProcessorInfo("b2"))
+            )
+        );
+        SearchPipelineInfo deserialized;
+        try (BytesStreamOutput bytesStreamOutput = new BytesStreamOutput()) {
+            bytesStreamOutput.setVersion(Version.V_2_7_0);
+            searchPipelineInfo.writeTo(bytesStreamOutput);
+            try (StreamInput bytesStreamInput = bytesStreamOutput.bytes().streamInput()) {
+                bytesStreamInput.setVersion(Version.V_2_7_0);
+                deserialized = new SearchPipelineInfo(bytesStreamInput);
+            }
+        }
+        for (String proc : List.of("a1", "a2", "a3", "b1", "b2")) {
+            assertTrue(deserialized.containsProcessor(Pipeline.REQUEST_PROCESSORS_KEY, proc));
+            assertTrue(deserialized.containsProcessor(Pipeline.RESPONSE_PROCESSORS_KEY, proc));
+        }
+    }
+}