FINERACT-2537: Add unit tests for the StreamResponseUtil

Tests cover:
- ok(StreamResponseData) response creation
- ok(AsyncResponse, StreamResponseData) asynchronous response handling
- Content-Disposition header generation
- StreamingOutput functionality
- Async response execution

These tests improve test coverage and help ensure correct behavior of response streaming utilities.

Author: Devi Pathak

fineract-core/src/test/java/org/apache/fineract/util/StreamResponseUtilTest.java

@@ -0,0 +1,137 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.fineract.util;
+
+import jakarta.ws.rs.container.AsyncResponse;
+import jakarta.ws.rs.core.HttpHeaders;
+import jakarta.ws.rs.core.Response;
+import jakarta.ws.rs.core.StreamingOutput;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+import java.util.concurrent.Future;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+
+class StreamResponseUtilTest {
+
+    @Test
+    void okReturnsResponseWithoutContentDispositionWhenDispositionTypeEmpty() {
+
+        InputStream stream = new ByteArrayInputStream("test".getBytes());
+
+        StreamResponseUtil.StreamResponseData data = StreamResponseUtil.StreamResponseData.builder().stream(stream).type("text/plain")
+                .fileName("file.txt").build();
+
+        Response response = StreamResponseUtil.ok(data);
+
+        Assertions.assertEquals("text/plain", response.getMediaType().toString());
+        Assertions.assertNull(response.getHeaderString(HttpHeaders.CONTENT_DISPOSITION));
+    }
+
+    @Test
+    void okReturnsResponseWithContentDispositionWhenDispositionTypePresent() {
+
+        InputStream stream = new ByteArrayInputStream("test".getBytes());
+
+        StreamResponseUtil.StreamResponseData data = StreamResponseUtil.StreamResponseData.builder().stream(stream).type("text/plain")
+                .fileName("file.txt").dispositionType(StreamResponseUtil.DISPOSITION_TYPE_ATTACHMENT).build();
+
+        Response response = StreamResponseUtil.ok(data);
+
+        Assertions.assertEquals("text/plain", response.getMediaType().toString());
+
+        String header = response.getHeaderString(HttpHeaders.CONTENT_DISPOSITION);
+
+        Assertions.assertNotNull(header);
+        Assertions.assertTrue(header.contains(StreamResponseUtil.DISPOSITION_TYPE_ATTACHMENT));
+        Assertions.assertTrue(header.contains("file.txt"));
+    }
+
+    @Test
+    void okAsyncResponseWithoutDisposition() throws Exception {
+
+        AsyncResponse asyncResponse = Mockito.mock(AsyncResponse.class);
+
+        InputStream stream = new ByteArrayInputStream("test".getBytes());
+
+        StreamResponseUtil.StreamResponseData data = StreamResponseUtil.StreamResponseData.builder().stream(stream).type("text/plain")
+                .build();
+
+        Future<?> future = StreamResponseUtil.ok(asyncResponse, data);
+
+        future.get();
+
+        Mockito.verify(asyncResponse).resume(Mockito.any(Response.class));
+    }
+
+    @Test
+    void okAsyncResponseWithDisposition() throws Exception {
+
+        AsyncResponse asyncResponse = Mockito.mock(AsyncResponse.class);
+
+        InputStream stream = new ByteArrayInputStream("test".getBytes());
+
+        StreamResponseUtil.StreamResponseData data = StreamResponseUtil.StreamResponseData.builder().stream(stream).type("text/plain")
+                .fileName("file.txt").dispositionType(StreamResponseUtil.DISPOSITION_TYPE_INLINE).build();
+
+        Future<?> future = StreamResponseUtil.ok(asyncResponse, data);
+
+        future.get();
+
+        Mockito.verify(asyncResponse).resume(Mockito.any(Response.class));
+    }
+
+    @Test
+    void okHeaderContainsCorrectFilename() {
+
+        InputStream stream = new ByteArrayInputStream("hello".getBytes());
+
+        StreamResponseUtil.StreamResponseData data = StreamResponseUtil.StreamResponseData.builder().stream(stream).type("text/plain")
+                .fileName("example.txt").dispositionType(StreamResponseUtil.DISPOSITION_TYPE_ATTACHMENT).build();
+
+        Response response = StreamResponseUtil.ok(data);
+
+        String header = response.getHeaderString(HttpHeaders.CONTENT_DISPOSITION);
+
+        Assertions.assertTrue(header.contains("attachment"));
+        Assertions.assertTrue(header.contains("example.txt"));
+    }
+
+    @Test
+    void okStreamingOutputWritesStreamData() throws Exception {
+
+        byte[] content = "stream-content".getBytes();
+        InputStream stream = new ByteArrayInputStream(content);
+
+        StreamResponseUtil.StreamResponseData data = StreamResponseUtil.StreamResponseData.builder().stream(stream).type("text/plain")
+                .build();
+
+        Response response = StreamResponseUtil.ok(data);
+
+        StreamingOutput streamingOutput = (StreamingOutput) response.getEntity();
+
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
+
+        streamingOutput.write(out);
+
+        Assertions.assertArrayEquals(content, out.toByteArray());
+    }
+}