Fix testPlainTextChunking (#92256)

This test had a (rare) off-by-one error in the computation of the number
of expected chunks, but also the calculations were kind of opaque and
contained too many magic numbers. This commit fixes the error and
reworks the calculations to be clearer.

Closes #92181

Author: DaveCTurner

server/src/test/java/org/elasticsearch/rest/action/cat/RestTableTests.java

@@ -11,6 +11,7 @@
 import org.apache.lucene.util.BytesRef;
 import org.elasticsearch.common.Table;
 import org.elasticsearch.common.recycler.Recycler;
+import org.elasticsearch.common.unit.ByteSizeUnit;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.rest.AbstractRestChannel;
 import org.elasticsearch.rest.RestResponse;
@@ -29,7 +30,6 @@
 
 import static org.elasticsearch.rest.action.cat.RestTable.buildDisplayHeaders;
 import static org.elasticsearch.rest.action.cat.RestTable.buildResponse;
-import static org.hamcrest.Matchers.allOf;
 import static org.hamcrest.Matchers.contains;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.equalToIgnoringCase;
@@ -259,22 +259,28 @@ public void testMultiSort() {
         assertEquals(Arrays.asList(1, 0, 2), rowOrder);
     }
 
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/92181")
     public void testPlainTextChunking() throws Exception {
+        final var cells = randomArray(8, 8, String[]::new, () -> randomAlphaOfLengthBetween(1, 5));
+        final var expectedRow = String.join(" ", cells) + "\n";
+
+        // OutputStreamWriter has an 8kiB buffer so all chunks are at least that big
+        final var bufferSize = ByteSizeUnit.KB.toIntBytes(8);
+        final var rowLength = expectedRow.length();
+        final var expectedRowsPerChunk = 1 + bufferSize / rowLength; // end chunk after first row which overflows the buffer
+        final var expectedChunkSize = expectedRowsPerChunk * rowLength;
+
+        final var rowCount = between(expectedRowsPerChunk + 1, expectedRowsPerChunk * 10);
+        final var expectedChunkCount = 1 + (rowCount * rowLength - 1) / expectedChunkSize; // ceil(rowCount * rowLength / expectedChunkSize)
+        assertThat(expectedChunkCount, greaterThan(1));
+
         final var expectedBody = new StringBuilder();
-        final var rowCount = between(10000, 20000);
         for (int i = 0; i < rowCount; i++) {
             table.startRow();
-            table.addCell("foo");
-            table.addCell("foo");
-            table.addCell("foo");
-            table.addCell("foo");
-            table.addCell("foo");
-            table.addCell("foo");
-            table.addCell("foo");
-            table.addCell("foo");
+            for (final var cell : cells) {
+                table.addCell(cell);
+            }
             table.endRow();
-            expectedBody.append(TEXT_TABLE_BODY);
+            expectedBody.append(expectedRow);
         }
 
         final var request = new FakeRestRequest.Builder(xContentRegistry()).withHeaders(
@@ -286,13 +292,10 @@ public void testPlainTextChunking() throws Exception {
             public void sendResponse(RestResponse response) {}
         });
 
-        // OutputStreamWriter has an 8kiB buffer so all chunks are at least that big anyway
-        final var bodyChunks = getBodyChunks(response, 8192);
-        final var rowLength = TEXT_TABLE_BODY.length();
-        final var expectedChunkSize = ((8193 + rowLength) / rowLength) * rowLength; // ceil(8193/rowLength) * rowLength
-        assertThat(bodyChunks.size(), allOf(greaterThan(1), equalTo((rowCount * rowLength + expectedChunkSize) / expectedChunkSize)));
-        assertThat(bodyChunks.get(0).length(), equalTo(expectedChunkSize));
-        assertEquals(expectedBody.toString(), String.join("", bodyChunks));
+        final var bodyChunks = getBodyChunks(response, bufferSize);
+        assertEquals("chunk count", expectedChunkCount, bodyChunks.size());
+        assertEquals("first chunk size", expectedChunkSize, bodyChunks.get(0).length());
+        assertEquals("body contents", expectedBody.toString(), String.join("", bodyChunks));
     }
 
     public void testEmptyTable() throws Exception {