GH-3267: Add comprehensive assertions to TestMemPageStore (#3268)

Author: ArnavBalyan

parquet-column/src/test/java/org/apache/parquet/column/mem/TestMemPageStore.java

@@ -20,11 +20,15 @@
 
 import static org.apache.parquet.column.Encoding.BIT_PACKED;
 import static org.apache.parquet.column.Encoding.PLAIN;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
 
 import java.io.IOException;
 import org.apache.parquet.bytes.BytesInput;
 import org.apache.parquet.column.ColumnDescriptor;
 import org.apache.parquet.column.page.DataPage;
+import org.apache.parquet.column.page.DataPageV1;
 import org.apache.parquet.column.page.PageReader;
 import org.apache.parquet.column.page.PageWriter;
 import org.apache.parquet.column.page.mem.MemPageStore;
@@ -46,19 +50,42 @@ public void test() throws IOException {
     ColumnDescriptor col = new ColumnDescriptor(path, PrimitiveTypeName.INT64, 2, 2);
     LongStatistics stats = new LongStatistics();
     PageWriter pageWriter = memPageStore.getPageWriter(col);
+
     pageWriter.writePage(BytesInput.from(new byte[735]), 209, stats, BIT_PACKED, BIT_PACKED, PLAIN);
     pageWriter.writePage(BytesInput.from(new byte[743]), 209, stats, BIT_PACKED, BIT_PACKED, PLAIN);
     pageWriter.writePage(BytesInput.from(new byte[743]), 209, stats, BIT_PACKED, BIT_PACKED, PLAIN);
     pageWriter.writePage(BytesInput.from(new byte[735]), 209, stats, BIT_PACKED, BIT_PACKED, PLAIN);
+
     PageReader pageReader = memPageStore.getPageReader(col);
     long totalValueCount = pageReader.getTotalValueCount();
-    LOG.info(String.valueOf(totalValueCount));
+    LOG.info("Total value count: " + totalValueCount);
+
+    assertEquals("Expected total value count to be 836 (4 pages * 209 values)", 836, totalValueCount);
+
     int total = 0;
+    int pageCount = 0;
     do {
       DataPage readPage = pageReader.readPage();
+
+      // Assert page was successfully read
+      assertNotNull("Page should not be null", readPage);
+      // Assert page has expected value count
+      assertEquals("Each page should have 209 values", 209, readPage.getValueCount());
+      // Assert encodings when the implementation is DataPageV1
+      assertTrue("Page should be an instance of DataPageV1", readPage instanceof DataPageV1);
+      if (readPage instanceof DataPageV1) {
+        DataPageV1 v1 = (DataPageV1) readPage;
+        assertEquals("Page repetition level encoding should be BIT_PACKED", BIT_PACKED, v1.getRlEncoding());
+        assertEquals("Page definition level encoding should be BIT_PACKED", BIT_PACKED, v1.getDlEncoding());
+        assertEquals("Page value encoding should be PLAIN", PLAIN, v1.getValueEncoding());
+      }
+
       total += readPage.getValueCount();
-      LOG.info(readPage.toString());
-      // TODO: assert
+      pageCount++;
     } while (total < totalValueCount);
+
+    // Assert we read exactly the expected number of pages and values
+    assertEquals("Should have read 4 pages", 4, pageCount);
+    assertEquals("Total values read should match totalValueCount", totalValueCount, total);
   }
 }