### Question:
SingleKeyValueTuple extends BaseTuple { @Override public String toString() { StringBuilder sb = new StringBuilder(); sb.append("SingleKeyValueTuple["); if (cell == null) { if (rowKeyPtr.get() == UNITIALIZED_KEY_BUFFER) { sb.append("null"); } else { sb.append(Bytes.toStringBinary(rowKeyPtr.get(),rowKeyPtr.getOffset(),rowKeyPtr.getLength())); } } else { sb.append(cell.toString()); } sb.append("]"); return sb.toString(); } SingleKeyValueTuple();  SingleKeyValueTuple(Cell cell); boolean hasKey(); void reset(); void setCell(Cell cell); void setKey(ImmutableBytesWritable ptr); void setKey(Cell cell); @Override void getKey(ImmutableBytesWritable ptr); @Override Cell getValue(byte[] cf, byte[] cq); @Override boolean isImmutable(); @Override String toString(); @Override int size(); @Override Cell getValue(int index); @Override boolean getValue(byte[] family, byte[] qualifier,
            ImmutableBytesWritable ptr);  }### Answer:
@Test public void testToString() { SingleKeyValueTuple singleKeyValueTuple = new SingleKeyValueTuple(); assertTrue(singleKeyValueTuple.toString().equals("SingleKeyValueTuple[null]")); final byte [] rowKey = Bytes.toBytes("aaa"); singleKeyValueTuple.setKey(new ImmutableBytesWritable(rowKey)); assertTrue(singleKeyValueTuple.toString().equals("SingleKeyValueTuple[aaa]")); byte [] family1 = Bytes.toBytes("abc"); byte [] qualifier1 = Bytes.toBytes("def"); KeyValue keyValue = new KeyValue(rowKey, family1, qualifier1, 0L, Type.Put, rowKey); singleKeyValueTuple = new SingleKeyValueTuple(keyValue); assertTrue(singleKeyValueTuple.toString().startsWith("SingleKeyValueTuple[aaa/abc:def/0/Put/vlen=3")); assertTrue(singleKeyValueTuple.toString().endsWith("]")); }