diff --git a/fastNLP/core/README.md b/fastNLP/core/README.md
deleted file mode 100644
index 8b137891..00000000
--- a/fastNLP/core/README.md
+++ /dev/null
@@ -1 +0,0 @@
-
diff --git a/fastNLP/core/action.py b/fastNLP/core/action.py
index d36d350d..c6cf2d63 100644
--- a/fastNLP/core/action.py
+++ b/fastNLP/core/action.py
@@ -4,88 +4,6 @@ import numpy as np
 import torch
 
 
-class Action(object):
-    """Operations shared by Trainer, Tester, or Inference.
-
-        This is designed for reducing replicate codes.
-            - make_batch: produce a min-batch of data. @staticmethod
-            - pad: padding method used in sequence modeling. @staticmethod
-            - mode: change network mode for either train or test. (for PyTorch) @staticmethod
-    """
-
-    def __init__(self):
-        super(Action, self).__init__()
-
-    @staticmethod
-    def make_batch(iterator, use_cuda, output_length=True, max_len=None):
-        """Batch and Pad data.
-
-        :param iterator: an iterator, (object that implements __next__ method) which returns the next sample.
-        :param use_cuda: bool, whether to use GPU
-        :param output_length: bool, whether to output the original length of the sequence before padding. (default: True)
-        :param max_len: int, maximum sequence length. Longer sequences will be clipped. (default: None)
-        :return :
-
-        if output_length is True,
-            (batch_x, seq_len): tuple of two elements
-                     batch_x: list. Each entry is a list of features of a sample. [batch_size, max_len]
-                     seq_len: list. The length of the pre-padded sequence, if output_length is True.
-            batch_y: list. Each entry is a list of labels of a sample.  [batch_size, num_labels]
-
-        if output_length is False,
-            batch_x: list. Each entry is a list of features of a sample. [batch_size, max_len]
-            batch_y: list. Each entry is a list of labels of a sample.  [batch_size, num_labels]
-        """
-        for batch in iterator:
-            batch_x = [sample[0] for sample in batch]
-            batch_y = [sample[1] for sample in batch]
-
-            batch_x = Action.pad(batch_x)
-            # pad batch_y only if it is a 2-level list
-            if len(batch_y) > 0 and isinstance(batch_y[0], list):
-                batch_y = Action.pad(batch_y)
-
-            # convert list to tensor
-            batch_x = convert_to_torch_tensor(batch_x, use_cuda)
-            batch_y = convert_to_torch_tensor(batch_y, use_cuda)
-
-            # trim data to max_len
-            if max_len is not None and batch_x.size(1) > max_len:
-                batch_x = batch_x[:, :max_len]
-
-            if output_length:
-                seq_len = [len(x) for x in batch_x]
-                yield (batch_x, seq_len), batch_y
-            else:
-                yield batch_x, batch_y
-
-    @staticmethod
-    def pad(batch, fill=0):
-        """ Pad a mini-batch of sequence samples to maximum length of this batch.
-
-        :param batch: list of list
-        :param fill: word index to pad, default 0.
-        :return batch: a padded mini-batch
-        """
-        max_length = max([len(x) for x in batch])
-        for idx, sample in enumerate(batch):
-            if len(sample) < max_length:
-                batch[idx] = sample + ([fill] * (max_length - len(sample)))
-        return batch
-
-    @staticmethod
-    def mode(model, is_test=False):
-        """Train mode or Test mode. This is for PyTorch currently.
-
-        :param model: a PyTorch model
-        :param is_test: bool, whether in test mode or not.
-        """
-        if is_test:
-            model.eval()
-        else:
-            model.train()
-
-
 def convert_to_torch_tensor(data_list, use_cuda):
     """Convert lists into (cuda) Tensors.
 
@@ -224,6 +142,7 @@ class BucketBatchifier(Batchifier):
     """Partition all samples into multiple buckets, each of which contains sentences of approximately the same length.
     In sampling, first random choose a bucket. Then sample data from it.
     The number of buckets is decided dynamically by the variance of sentence lengths.
+    TODO: merge it into Batch
     """
 
     def __init__(self, data_set, batch_size, num_buckets, drop_last=True, sampler=None):
diff --git a/fastNLP/core/dataset.py b/fastNLP/core/dataset.py
index 5f749795..bb1a1890 100644
--- a/fastNLP/core/dataset.py
+++ b/fastNLP/core/dataset.py
@@ -1,8 +1,77 @@
 from collections import defaultdict
 
+from fastNLP.core.field import TextField
+from fastNLP.core.instance import Instance
+
+
+def create_dataset_from_lists(str_lists: list, word_vocab: dict, has_target: bool = False, label_vocab: dict = None):
+    if has_target is True:
+        if label_vocab is None:
+            raise RuntimeError("Must provide label vocabulary to transform labels.")
+        return create_labeled_dataset_from_lists(str_lists, word_vocab, label_vocab)
+    else:
+        return create_unlabeled_dataset_from_lists(str_lists, word_vocab)
+
+
+def create_labeled_dataset_from_lists(str_lists, word_vocab, label_vocab):
+    """Create an DataSet instance that contains labels.
+
+    :param str_lists: list of list of strings, [num_examples, 2, *].
+            ::
+            [
+                [[word_11, word_12, ...], [label_11, label_12, ...]],
+                ...
+            ]
+
+    :param word_vocab: dict of (str: int), which means (word: index).
+    :param label_vocab: dict of (str: int), which means (word: index).
+    :return data_set: a DataSet instance.
+
+    """
+    data_set = DataSet()
+    for example in str_lists:
+        word_seq, label_seq = example[0], example[1]
+        x = TextField(word_seq, is_target=False)
+        y = TextField(label_seq, is_target=True)
+        data_set.append(Instance(word_seq=x, label_seq=y))
+    data_set.index_field("word_seq", word_vocab)
+    data_set.index_field("label_seq", label_vocab)
+    return data_set
+
+
+def create_unlabeled_dataset_from_lists(str_lists, word_vocab):
+    """Create an DataSet instance that contains no labels.
+
+    :param str_lists: list of list of strings, [num_examples, *].
+            ::
+            [
+                [word_11, word_12, ...],
+                ...
+            ]
+
+    :param word_vocab: dict of (str: int), which means (word: index).
+    :return data_set: a DataSet instance.
+
+    """
+    data_set = DataSet()
+    for word_seq in str_lists:
+        x = TextField(word_seq, is_target=False)
+        data_set.append(Instance(word_seq=x))
+    data_set.index_field("word_seq", word_vocab)
+    return data_set
+
 
 class DataSet(list):
+    """A DataSet object is a list of Instance objects.
+
+    """
     def __init__(self, name="", instances=None):
+        """
+
+        :param name: str, the name of the dataset. (default: "")
+        :param instances: list of Instance objects. (default: None)
+
+        """
         list.__init__([])
         self.name = name
         if instances is not None:
diff --git a/fastNLP/core/field.py b/fastNLP/core/field.py
index 1efa759a..f5347bd6 100644
--- a/fastNLP/core/field.py
+++ b/fastNLP/core/field.py
@@ -20,9 +20,10 @@ class Field(object):
 
 
 class TextField(Field):
-    def __init__(self, text: list, is_target):
+    def __init__(self, text, is_target):
         """
-        :param list text:
+        :param text: list of strings
+        :param is_target: bool
         """
         super(TextField, self).__init__(is_target)
         self.text = text
@@ -32,7 +33,7 @@ class TextField(Field):
         if self._index is None:
             self._index = [vocab[c] for c in self.text]
         else:
-            print('error')
+            raise RuntimeError("Replicate indexing of this field.")
         return self._index
 
     def get_length(self):
diff --git a/fastNLP/core/instance.py b/fastNLP/core/instance.py
index 3322e576..32f95197 100644
--- a/fastNLP/core/instance.py
+++ b/fastNLP/core/instance.py
@@ -41,7 +41,7 @@ class Instance(object):
         :param padding_length: dict of (str: int), which means (field name: padding_length of this field)
         :return tensor_x: dict of (str: torch.LongTensor), which means (field name: tensor of shape [padding_length, ])
                 tensor_y: dict of (str: torch.LongTensor), which means (field name: tensor of shape [padding_length, ])
-
+                        If is_target is False for all fields, tensor_y would be an empty dict.
         """
         tensor_x = {}
         tensor_y = {}
diff --git a/fastNLP/core/predictor.py b/fastNLP/core/predictor.py
index d04a6ef0..802661ef 100644
--- a/fastNLP/core/predictor.py
+++ b/fastNLP/core/predictor.py
@@ -1,53 +1,10 @@
 import numpy as np
 import torch
 
-from fastNLP.core.action import Batchifier, SequentialSampler
-from fastNLP.core.action import convert_to_torch_tensor
-from fastNLP.core.preprocess import load_pickle, DEFAULT_UNKNOWN_LABEL
-from fastNLP.modules import utils
-
-
-def make_batch(iterator, use_cuda, output_length=False, max_len=None, min_len=None):
-    """Batch and Pad data, only for Inference.
-
-    :param iterator: An iterable object that returns a list of indices representing a mini-batch of samples.
-    :param use_cuda: bool, whether to use GPU
-    :param output_length: bool, whether to output the original length of the sequence before padding. (default: False)
-    :param max_len: int, maximum sequence length. Longer sequences will be clipped. (default: None)
-    :param min_len: int, minimum sequence length. Shorter sequences will be padded. (default: None)
-    :return:
-    """
-    for batch_x in iterator:
-        batch_x = pad(batch_x)
-        # convert list to tensor
-        batch_x = convert_to_torch_tensor(batch_x, use_cuda)
-
-        # trim data to max_len
-        if max_len is not None and batch_x.size(1) > max_len:
-            batch_x = batch_x[:, :max_len]
-        if min_len is not None and batch_x.size(1) < min_len:
-            pad_tensor = torch.zeros(batch_x.size(0), min_len - batch_x.size(1)).to(batch_x)
-            batch_x = torch.cat((batch_x, pad_tensor), 1)
-
-        if output_length:
-            seq_len = [len(x) for x in batch_x]
-            yield tuple([batch_x, seq_len])
-        else:
-            yield batch_x
-
-
-def pad(batch, fill=0):
-    """ Pad a mini-batch of sequence samples to maximum length of this batch.
-
-    :param batch: list of list
-    :param fill: word index to pad, default 0.
-    :return batch: a padded mini-batch
-    """
-    max_length = max([len(x) for x in batch])
-    for idx, sample in enumerate(batch):
-        if len(sample) < max_length:
-            batch[idx] = sample + ([fill] * (max_length - len(sample)))
-    return batch
+from fastNLP.core.action import SequentialSampler
+from fastNLP.core.batch import Batch
+from fastNLP.core.dataset import create_dataset_from_lists
+from fastNLP.core.preprocess import load_pickle
 
 
 class Predictor(object):
@@ -59,11 +16,17 @@ class Predictor(object):
     Currently, Predictor does not support GPU.
     """
 
-    def __init__(self, pickle_path):
+    def __init__(self, pickle_path, task):
+        """
+
+        :param pickle_path: str, the path to the pickle files.
+        :param task: str, specify which task the predictor will perform. One of ("seq_label", "text_classify").
+
+        """
         self.batch_size = 1
         self.batch_output = []
-        self.iterator = None
         self.pickle_path = pickle_path
+        self._task = task  # one of ("seq_label", "text_classify")
         self.index2label = load_pickle(self.pickle_path, "id2class.pkl")
         self.word2index = load_pickle(self.pickle_path, "word2id.pkl")
 
@@ -71,19 +34,19 @@ class Predictor(object):
         """Perform inference using the trained model.
 
         :param network: a PyTorch model (cpu)
-        :param data: list of list of strings
+        :param data: list of list of strings, [num_examples, seq_len]
         :return: list of list of strings, [num_examples, tag_seq_length]
         """
-        # transform strings into indices
+        # transform strings into DataSet object
         data = self.prepare_input(data)
 
         # turn on the testing mode; clean up the history
         self.mode(network, test=True)
         self.batch_output.clear()
 
-        data_iterator = iter(Batchifier(SequentialSampler(data), self.batch_size, drop_last=False))
+        data_iterator = Batch(data, batch_size=self.batch_size, sampler=SequentialSampler(), use_cuda=False)
 
-        for batch_x in self.make_batch(data_iterator, use_cuda=False):
+        for batch_x, _ in data_iterator:
             with torch.no_grad():
                 prediction = self.data_forward(network, batch_x)
 
@@ -99,103 +62,61 @@ class Predictor(object):
 
     def data_forward(self, network, x):
         """Forward through network."""
-        raise NotImplementedError
-
-    def make_batch(self, iterator, use_cuda):
-        raise NotImplementedError
+        y = network(**x)
+        if self._task == "seq_label":
+            y = network.prediction(y)
+        return y
 
     def prepare_input(self, data):
-        """Transform two-level list of strings into that of index.
+        """Transform two-level list of strings into an DataSet object.
+        In the training pipeline, this is done by Preprocessor. But in inference time, we do not call Preprocessor.
 
-        :param data:
+        :param data: list of list of strings.
+                ::
                 [
                     [word_11, word_12, ...],
                     [word_21, word_22, ...],
                     ...
                 ]
-        :return data_index: list of list of int.
+
+        :return data_set: a DataSet instance.
         """
         assert isinstance(data, list)
-        data_index = []
-        default_unknown_index = self.word2index[DEFAULT_UNKNOWN_LABEL]
-        for example in data:
-            data_index.append([self.word2index.get(w, default_unknown_index) for w in example])
-        return data_index
+        return create_dataset_from_lists(data, self.word2index, has_target=False)
 
     def prepare_output(self, data):
         """Transform list of batch outputs into strings."""
-        raise NotImplementedError
-
-
-class SeqLabelInfer(Predictor):
-    """
-    Inference on sequence labeling models.
-    """
-
-    def __init__(self, pickle_path):
-        super(SeqLabelInfer, self).__init__(pickle_path)
+        if self._task == "seq_label":
+            return self._seq_label_prepare_output(data)
+        elif self._task == "text_classify":
+            return self._text_classify_prepare_output(data)
+        else:
+            raise NotImplementedError("Unknown task type {}".format(self._task))
 
-    def data_forward(self, network, inputs):
-        """
-        This is only for sequence labeling with CRF decoder.
-        :param network: a PyTorch model
-        :param inputs: tuple of (x, seq_len)
-                        x: Tensor of shape [batch_size, max_len], where max_len is the maximum length of the mini-batch
-                            after padding.
-                        seq_len: list of int, the lengths of sequences before padding.
-        :return prediction: Tensor of shape [batch_size, max_len]
-        """
-        if not isinstance(inputs[1], list) and isinstance(inputs[0], list):
-            raise RuntimeError("output_length must be true for sequence modeling.")
-        # unpack the returned value from make_batch
-        x, seq_len = inputs[0], inputs[1]
-        batch_size, max_len = x.size(0), x.size(1)
-        mask = utils.seq_mask(seq_len, max_len)
-        mask = mask.byte().view(batch_size, max_len)
-        y = network(x)
-        prediction = network.prediction(y, mask)
-        return torch.Tensor(prediction)
-
-    def make_batch(self, iterator, use_cuda):
-        return make_batch(iterator, use_cuda, output_length=True)
-
-    def prepare_output(self, batch_outputs):
-        """Transform list of batch outputs into strings.
-
-        :param batch_outputs: list of 2-D Tensor, shape [num_batch, batch-size, tag_seq_length].
-        :return results: 2-D list of strings, shape [num_examples, tag_seq_length]
-        """
+    def _seq_label_prepare_output(self, batch_outputs):
         results = []
         for batch in batch_outputs:
             for example in np.array(batch):
                 results.append([self.index2label[int(x)] for x in example])
         return results
 
-
-class ClassificationInfer(Predictor):
-    """
-    Inference on Classification models.
-    """
-
-    def __init__(self, pickle_path):
-        super(ClassificationInfer, self).__init__(pickle_path)
-
-    def data_forward(self, network, x):
-        """Forward through network."""
-        logits = network(x)
-        return logits
-
-    def make_batch(self, iterator, use_cuda):
-        return make_batch(iterator, use_cuda, output_length=False, min_len=5)
-
-    def prepare_output(self, batch_outputs):
-        """
-        Transform list of batch outputs into strings.
-        :param batch_outputs: list of 2-D Tensor, of shape [num_batch, batch-size, num_classes].
-        :return results: list of strings
-        """
+    def _text_classify_prepare_output(self, batch_outputs):
         results = []
         for batch_out in batch_outputs:
             idx = np.argmax(batch_out.detach().numpy(), axis=-1)
             results.extend([self.index2label[i] for i in idx])
         return results
+
+
+class SeqLabelInfer(Predictor):
+    def __init__(self, pickle_path):
+        print(
+            "[FastNLP Warning] SeqLabelInfer will be deprecated. Please use Predictor with argument 'task'='seq_label'.")
+        super(SeqLabelInfer, self).__init__(pickle_path, "seq_label")
+
+
+class ClassificationInfer(Predictor):
+    def __init__(self, pickle_path):
+        print(
+            "[FastNLP Warning] ClassificationInfer will be deprecated. Please use Predictor with argument 'task'='text_classify'.")
+        super(ClassificationInfer, self).__init__(pickle_path, "text_classify")
diff --git a/fastNLP/core/tester.py b/fastNLP/core/tester.py
index f23ab704..aaa96283 100644
--- a/fastNLP/core/tester.py
+++ b/fastNLP/core/tester.py
@@ -1,7 +1,6 @@
 import numpy as np
 import torch
 
-from fastNLP.core.action import Action
 from fastNLP.core.action import RandomSampler
 from fastNLP.core.batch import Batch
 from fastNLP.saver.logger import create_logger
@@ -79,7 +78,7 @@ class BaseTester(object):
             self._model = network
 
         # turn on the testing mode; clean up the history
-        self.mode(network, test=True)
+        self.mode(network, is_test=True)
         self.eval_history.clear()
         self.batch_output.clear()
 
@@ -102,13 +101,17 @@ class BaseTester(object):
                 print(self.make_eval_output(prediction, eval_results))
             step += 1
 
-    def mode(self, model, test):
+    def mode(self, model, is_test=False):
         """Train mode or Test mode. This is for PyTorch currently.
 
         :param model: a PyTorch model
-        :param test: bool, whether in test mode.
+        :param is_test: bool, whether in test mode or not.
+
         """
-        Action.mode(model, test)
+        if is_test:
+            model.eval()
+        else:
+            model.train()
 
     def data_forward(self, network, x):
         """A forward pass of the model. """
diff --git a/fastNLP/core/trainer.py b/fastNLP/core/trainer.py
index 1405f156..e638fdde 100644
--- a/fastNLP/core/trainer.py
+++ b/fastNLP/core/trainer.py
@@ -6,7 +6,6 @@ from datetime import timedelta
 import torch
 from tensorboardX import SummaryWriter
 
-from fastNLP.core.action import Action
 from fastNLP.core.action import RandomSampler
 from fastNLP.core.batch import Batch
 from fastNLP.core.loss import Loss
@@ -126,7 +125,7 @@ class BaseTrainer(object):
             logger.info("training epoch {}".format(epoch))
 
             # turn on network training mode
-            self.mode(network, test=False)
+            self.mode(network, is_test=False)
             # prepare mini-batch iterator
             data_iterator = Batch(train_data, batch_size=self.batch_size, sampler=RandomSampler(),
                                   use_cuda=self.use_cuda)
@@ -201,8 +200,17 @@ class BaseTrainer(object):
             network_copy = copy.deepcopy(network)
             self.train(network_copy, train_data_cv[i], dev_data_cv[i])
 
-    def mode(self, network, test):
-        Action.mode(network, test)
+    def mode(self, model, is_test=False):
+        """Train mode or Test mode. This is for PyTorch currently.
+
+        :param model: a PyTorch model
+        :param is_test: bool, whether in test mode or not.
+
+        """
+        if is_test:
+            model.eval()
+        else:
+            model.train()
 
     def define_optimizer(self):
         """Define framework-specific optimizer specified by the models.
@@ -284,7 +292,7 @@ class BaseTrainer(object):
         :param validator: a Tester instance
         :return: bool, True means current results on dev set is the best.
         """
-        loss, accuracy = validator.metrics()
+        loss, accuracy = validator.metrics
         if accuracy > self._best_accuracy:
             self._best_accuracy = accuracy
             return True
diff --git a/fastNLP/models/sequence_modeling.py b/fastNLP/models/sequence_modeling.py
index 8d194947..c2bcc693 100644
--- a/fastNLP/models/sequence_modeling.py
+++ b/fastNLP/models/sequence_modeling.py
@@ -62,6 +62,8 @@ class SeqLabeling(BaseModel):
         """
         x = x.float()
         y = y.long()
+        assert x.shape[:2] == y.shape
+        assert y.shape == self.mask.shape
         total_loss = self.Crf(x, y, self.mask)
         return torch.mean(total_loss)
 
diff --git a/test/core/test_action.py b/test/core/test_action.py
deleted file mode 100644
index 8d0f628b..00000000
--- a/test/core/test_action.py
+++ /dev/null
@@ -1,17 +0,0 @@
-import unittest
-
-from fastNLP.core.action import Action, Batchifier, SequentialSampler
-
-
-class TestAction(unittest.TestCase):
-    def test_case_1(self):
-        x = [1, 2, 3, 4, 5, 6, 7, 8]
-        y = [1, 1, 1, 1, 2, 2, 2, 2]
-        data = []
-        for i in range(len(x)):
-            data.append([[x[i]], [y[i]]])
-        data = Batchifier(SequentialSampler(data), batch_size=2, drop_last=False)
-        action = Action()
-        for batch_x in action.make_batch(data, use_cuda=False, output_length=True, max_len=None):
-            print(batch_x)
-
diff --git a/test/core/test_batch.py b/test/core/test_batch.py
new file mode 100644
index 00000000..395aeb2b
--- /dev/null
+++ b/test/core/test_batch.py
@@ -0,0 +1,62 @@
+import unittest
+
+import torch
+
+from fastNLP.core.batch import Batch
+from fastNLP.core.dataset import DataSet, create_dataset_from_lists
+from fastNLP.core.field import TextField, LabelField
+from fastNLP.core.instance import Instance
+
+raw_texts = ["i am a cat",
+             "this is a test of new batch",
+             "ha ha",
+             "I am a good boy .",
+             "This is the most beautiful girl ."
+             ]
+texts = [text.strip().split() for text in raw_texts]
+labels = [0, 1, 0, 0, 1]
+
+# prepare vocabulary
+vocab = {}
+for text in texts:
+    for tokens in text:
+        if tokens not in vocab:
+            vocab[tokens] = len(vocab)
+
+
+class TestCase1(unittest.TestCase):
+    def test(self):
+        data = DataSet()
+        for text, label in zip(texts, labels):
+            x = TextField(text, is_target=False)
+            y = LabelField(label, is_target=True)
+            ins = Instance(text=x, label=y)
+            data.append(ins)
+
+        # use vocabulary to index data
+        data.index_field("text", vocab)
+
+        # define naive sampler for batch class
+        class SeqSampler:
+            def __call__(self, dataset):
+                return list(range(len(dataset)))
+
+        # use batch to iterate dataset
+        data_iterator = Batch(data, 2, SeqSampler(), False)
+        for batch_x, batch_y in data_iterator:
+            self.assertEqual(len(batch_x), 2)
+            self.assertTrue(isinstance(batch_x, dict))
+            self.assertTrue(isinstance(batch_x["text"], torch.LongTensor))
+            self.assertTrue(isinstance(batch_y, dict))
+            self.assertTrue(isinstance(batch_y["label"], torch.LongTensor))
+
+
+class TestCase2(unittest.TestCase):
+    def test(self):
+        data = DataSet()
+        for text in texts:
+            x = TextField(text, is_target=False)
+            ins = Instance(text=x)
+            data.append(ins)
+        data_set = create_dataset_from_lists(texts, vocab, has_target=False)
+        self.assertTrue(type(data) == type(data_set))
diff --git a/test/core/test_predictor.py b/test/core/test_predictor.py
new file mode 100644
index 00000000..c7ad65d7
--- /dev/null
+++ b/test/core/test_predictor.py
@@ -0,0 +1,51 @@
+import os
+import unittest
+
+from fastNLP.core.predictor import Predictor
+from fastNLP.core.preprocess import save_pickle
+from fastNLP.models.sequence_modeling import SeqLabeling
+
+
+class TestPredictor(unittest.TestCase):
+    def test_seq_label(self):
+        model_args = {
+            "vocab_size": 10,
+            "word_emb_dim": 100,
+            "rnn_hidden_units": 100,
+            "num_classes": 5
+        }
+
+        infer_data = [
+            ['a', 'b', 'c', 'd', 'e'],
+            ['a', '@', 'c', 'd', 'e'],
+            ['a', 'b', '#', 'd', 'e'],
+            ['a', 'b', 'c', '?', 'e'],
+            ['a', 'b', 'c', 'd', '$'],
+            ['!', 'b', 'c', 'd', 'e']
+        ]
+        vocab = {'a': 0, 'b': 1, 'c': 2, 'd': 3, 'e': 4, '!': 5, '@': 6, '#': 7, '$': 8, '?': 9}
+
+        os.system("mkdir save")
+        save_pickle({0: "0", 1: "1", 2: "2", 3: "3", 4: "4"}, "./save/", "id2class.pkl")
+        save_pickle(vocab, "./save/", "word2id.pkl")
+
+        model = SeqLabeling(model_args)
+        predictor = Predictor("./save/", task="seq_label")
+
+        results = predictor.predict(network=model, data=infer_data)
+
+        self.assertTrue(isinstance(results, list))
+        self.assertGreater(len(results), 0)
+        for res in results:
+            self.assertTrue(isinstance(res, list))
+            self.assertEqual(len(res), 5)
+            self.assertTrue(isinstance(res[0], str))
+
+        os.system("rm -rf save")
+        print("pickle path deleted")
+
+
+class TestPredictor2(unittest.TestCase):
+    def test_text_classify(self):
+        # TODO
+        pass
diff --git a/test/core/test_preprocess.py b/test/core/test_preprocess.py
index bff33ed3..05c04ce9 100644
--- a/test/core/test_preprocess.py
+++ b/test/core/test_preprocess.py
@@ -1,24 +1,25 @@
 import os
 import unittest
 
+from fastNLP.core.dataset import DataSet
 from fastNLP.core.preprocess import SeqLabelPreprocess
 
+data = [
+    [['Tom', 'and', 'Jerry', '.'], ['n', '&', 'n', '.']],
+    [['Hello', 'world', '!'], ['a', 'n', '.']],
+    [['Tom', 'and', 'Jerry', '.'], ['n', '&', 'n', '.']],
+    [['Hello', 'world', '!'], ['a', 'n', '.']],
+    [['Tom', 'and', 'Jerry', '.'], ['n', '&', 'n', '.']],
+    [['Hello', 'world', '!'], ['a', 'n', '.']],
+    [['Tom', 'and', 'Jerry', '.'], ['n', '&', 'n', '.']],
+    [['Hello', 'world', '!'], ['a', 'n', '.']],
+    [['Tom', 'and', 'Jerry', '.'], ['n', '&', 'n', '.']],
+    [['Hello', 'world', '!'], ['a', 'n', '.']],
+]
 
-class TestSeqLabelPreprocess(unittest.TestCase):
-    def test_case_1(self):
-        data = [
-            [['Tom', 'and', 'Jerry', '.'], ['n', '&', 'n', '.']],
-            [['Hello', 'world', '!'], ['a', 'n', '.']],
-            [['Tom', 'and', 'Jerry', '.'], ['n', '&', 'n', '.']],
-            [['Hello', 'world', '!'], ['a', 'n', '.']],
-            [['Tom', 'and', 'Jerry', '.'], ['n', '&', 'n', '.']],
-            [['Hello', 'world', '!'], ['a', 'n', '.']],
-            [['Tom', 'and', 'Jerry', '.'], ['n', '&', 'n', '.']],
-            [['Hello', 'world', '!'], ['a', 'n', '.']],
-            [['Tom', 'and', 'Jerry', '.'], ['n', '&', 'n', '.']],
-            [['Hello', 'world', '!'], ['a', 'n', '.']],
-        ]
 
+class TestCase1(unittest.TestCase):
+    def test(self):
         if os.path.exists("./save"):
             for root, dirs, files in os.walk("./save", topdown=False):
                 for name in files:
@@ -27,17 +28,45 @@ class TestSeqLabelPreprocess(unittest.TestCase):
                     os.rmdir(os.path.join(root, name))
         result = SeqLabelPreprocess().run(train_dev_data=data, train_dev_split=0.4,
                                           pickle_path="./save")
-        result = SeqLabelPreprocess().run(train_dev_data=data, train_dev_split=0.4,
-                                          pickle_path="./save")
+        self.assertEqual(len(result), 2)
+        self.assertEqual(type(result[0]), DataSet)
+        self.assertEqual(type(result[1]), DataSet)
+
+        os.system("rm -rf save")
+        print("pickle path deleted")
+
+
+class TestCase2(unittest.TestCase):
+    def test(self):
         if os.path.exists("./save"):
             for root, dirs, files in os.walk("./save", topdown=False):
                 for name in files:
                     os.remove(os.path.join(root, name))
                 for name in dirs:
                     os.rmdir(os.path.join(root, name))
-        result = SeqLabelPreprocess().run(test_data=data, train_dev_data=data,
-                                                           pickle_path="./save", train_dev_split=0.4,
-                                                           cross_val=True)
         result = SeqLabelPreprocess().run(test_data=data, train_dev_data=data,
                                           pickle_path="./save", train_dev_split=0.4,
-                                          cross_val=True)
+                                          cross_val=False)
+        self.assertEqual(len(result), 3)
+        self.assertEqual(type(result[0]), DataSet)
+        self.assertEqual(type(result[1]), DataSet)
+        self.assertEqual(type(result[2]), DataSet)
+
+        os.system("rm -rf save")
+        print("pickle path deleted")
+
+
+class TestCase3(unittest.TestCase):
+    def test(self):
+        num_folds = 2
+        result = SeqLabelPreprocess().run(test_data=None, train_dev_data=data,
+                                          pickle_path="./save", train_dev_split=0.4,
+                                          cross_val=True, n_fold=num_folds)
+        self.assertEqual(len(result), 2)
+        self.assertEqual(len(result[0]), num_folds)
+        self.assertEqual(len(result[1]), num_folds)
+        for data_set in result[0] + result[1]:
+            self.assertEqual(type(data_set), DataSet)
+
+        os.system("rm -rf save")
+        print("pickle path deleted")
diff --git a/test/core/test_tester.py b/test/core/test_tester.py
index e4ccf536..aa277b9a 100644
--- a/test/core/test_tester.py
+++ b/test/core/test_tester.py
@@ -1,37 +1,55 @@
-from fastNLP.core.preprocess import SeqLabelPreprocess
+import os
+import unittest
+
+from fastNLP.core.dataset import DataSet
+from fastNLP.core.field import TextField
+from fastNLP.core.instance import Instance
 from fastNLP.core.tester import SeqLabelTester
-from fastNLP.loader.config_loader import ConfigSection, ConfigLoader
-from fastNLP.loader.dataset_loader import TokenizeDatasetLoader
 from fastNLP.models.sequence_modeling import SeqLabeling
 
 data_name = "pku_training.utf8"
 pickle_path = "data_for_tests"
 
 
-def foo():
-    loader = TokenizeDatasetLoader("./data_for_tests/cws_pku_utf_8")
-    train_data = loader.load_pku()
-
-    train_args = ConfigSection()
-    ConfigLoader("config.cfg").load_config("./data_for_tests/config", {"POS": train_args})
-
-    # Preprocessor
-    p = SeqLabelPreprocess()
-    train_data = p.run(train_data)
-    train_args["vocab_size"] = p.vocab_size
-    train_args["num_classes"] = p.num_classes
-
-    model = SeqLabeling(train_args)
-
-    valid_args = {"save_output": True, "validate_in_training": True, "save_dev_input": True,
-                  "save_loss": True, "batch_size": 8, "pickle_path": "./data_for_tests/",
-                  "use_cuda": True}
-    validator = SeqLabelTester(**valid_args)
-
-    print("start validation.")
-    validator.test(model, train_data)
-    print(validator.show_metrics())
-
-
-if __name__ == "__main__":
-    foo()
+class TestTester(unittest.TestCase):
+    def test_case_1(self):
+        model_args = {
+            "vocab_size": 10,
+            "word_emb_dim": 100,
+            "rnn_hidden_units": 100,
+            "num_classes": 5
+        }
+        valid_args = {"save_output": True, "validate_in_training": True, "save_dev_input": True,
+                      "save_loss": True, "batch_size": 2, "pickle_path": "./save/",
+                      "use_cuda": False, "print_every_step": 1}
+
+        train_data = [
+            [['a', 'b', 'c', 'd', 'e'], ['a', '@', 'c', 'd', 'e']],
+            [['a', '@', 'c', 'd', 'e'], ['a', '@', 'c', 'd', 'e']],
+            [['a', 'b', '#', 'd', 'e'], ['a', '@', 'c', 'd', 'e']],
+            [['a', 'b', 'c', '?', 'e'], ['a', '@', 'c', 'd', 'e']],
+            [['a', 'b', 'c', 'd', '$'], ['a', '@', 'c', 'd', 'e']],
+            [['!', 'b', 'c', 'd', 'e'], ['a', '@', 'c', 'd', 'e']],
+        ]
+        vocab = {'a': 0, 'b': 1, 'c': 2, 'd': 3, 'e': 4, '!': 5, '@': 6, '#': 7, '$': 8, '?': 9}
+        label_vocab = {'a': 0, '@': 1, 'c': 2, 'd': 3, 'e': 4}
+
+        data_set = DataSet()
+        for example in train_data:
+            text, label = example[0], example[1]
+            x = TextField(text, False)
+            y = TextField(label, is_target=True)
+            ins = Instance(word_seq=x, label_seq=y)
+            data_set.append(ins)
+
+        data_set.index_field("word_seq", vocab)
+        data_set.index_field("label_seq", label_vocab)
+
+        model = SeqLabeling(model_args)
+
+        tester = SeqLabelTester(**valid_args)
+        tester.test(network=model, dev_data=data_set)
+        # If this can run, everything is OK.
+
+        os.system("rm -rf save")
+        print("pickle path deleted")
diff --git a/test/core/test_trainer.py b/test/core/test_trainer.py
index 7db861af..c71cd695 100644
--- a/test/core/test_trainer.py
+++ b/test/core/test_trainer.py
@@ -1,33 +1,54 @@
 import os
-
-import torch.nn as nn
 import unittest
 
-from fastNLP.core.trainer import SeqLabelTrainer
+from fastNLP.core.dataset import DataSet
+from fastNLP.core.field import TextField
+from fastNLP.core.instance import Instance
 from fastNLP.core.loss import Loss
 from fastNLP.core.optimizer import Optimizer
+from fastNLP.core.trainer import SeqLabelTrainer
 from fastNLP.models.sequence_modeling import SeqLabeling
 
+
 class TestTrainer(unittest.TestCase):
     def test_case_1(self):
-        args = {"epochs": 3, "batch_size": 8, "validate": True, "use_cuda": True, "pickle_path": "./save/",
+        args = {"epochs": 3, "batch_size": 2, "validate": True, "use_cuda": False, "pickle_path": "./save/",
                 "save_best_dev": True, "model_name": "default_model_name.pkl",
                 "loss": Loss(None),
                 "optimizer": Optimizer("Adam", lr=0.001, weight_decay=0),
-                "vocab_size": 20,
+                "vocab_size": 10,
                 "word_emb_dim": 100,
                 "rnn_hidden_units": 100,
-                "num_classes": 3
+                "num_classes": 5
                 }
-        trainer = SeqLabelTrainer()
+        trainer = SeqLabelTrainer(**args)
+
         train_data = [
-            [[1, 2, 3, 4, 5, 6], [1, 0, 1, 0, 1, 2]],
-            [[2, 3, 4, 5, 1, 6], [0, 1, 0, 1, 0, 2]],
-            [[1, 4, 1, 4, 1, 6], [1, 0, 1, 0, 1, 2]],
-            [[1, 2, 3, 4, 5, 6], [1, 0, 1, 0, 1, 2]],
-            [[2, 3, 4, 5, 1, 6], [0, 1, 0, 1, 0, 2]],
-            [[1, 4, 1, 4, 1, 6], [1, 0, 1, 0, 1, 2]],
+            [['a', 'b', 'c', 'd', 'e'], ['a', '@', 'c', 'd', 'e']],
+            [['a', '@', 'c', 'd', 'e'], ['a', '@', 'c', 'd', 'e']],
+            [['a', 'b', '#', 'd', 'e'], ['a', '@', 'c', 'd', 'e']],
+            [['a', 'b', 'c', '?', 'e'], ['a', '@', 'c', 'd', 'e']],
+            [['a', 'b', 'c', 'd', '$'], ['a', '@', 'c', 'd', 'e']],
+            [['!', 'b', 'c', 'd', 'e'], ['a', '@', 'c', 'd', 'e']],
         ]
-        dev_data = train_data
+        vocab = {'a': 0, 'b': 1, 'c': 2, 'd': 3, 'e': 4, '!': 5, '@': 6, '#': 7, '$': 8, '?': 9}
+        label_vocab = {'a': 0, '@': 1, 'c': 2, 'd': 3, 'e': 4}
+
+        data_set = DataSet()
+        for example in train_data:
+            text, label = example[0], example[1]
+            x = TextField(text, False)
+            y = TextField(label, is_target=True)
+            ins = Instance(word_seq=x, label_seq=y)
+            data_set.append(ins)
+
+        data_set.index_field("word_seq", vocab)
+        data_set.index_field("label_seq", label_vocab)
+
         model = SeqLabeling(args)
-        trainer.train(network=model, train_data=train_data, dev_data=dev_data)
\ No newline at end of file
+
+        trainer.train(network=model, train_data=data_set, dev_data=data_set)
+        # If this can run, everything is OK.
+
+        os.system("rm -rf save")
+        print("pickle path deleted")
diff --git a/test/model/test_charlm.py b/test/model/test_charlm.py
deleted file mode 100644
index e76f6404..00000000
--- a/test/model/test_charlm.py
+++ /dev/null
@@ -1,8 +0,0 @@
-
-
-def test_charlm():
-    pass
-
-
-if __name__ == "__main__":
-    test_charlm()
diff --git a/test/model/test_seq_label.py b/test/model/test_seq_label.py
new file mode 100644
index 00000000..9a0c46cd
--- /dev/null
+++ b/test/model/test_seq_label.py
@@ -0,0 +1,96 @@
+import argparse
+import os
+
+from fastNLP.core.optimizer import Optimizer
+from fastNLP.core.preprocess import SeqLabelPreprocess
+from fastNLP.core.tester import SeqLabelTester
+from fastNLP.core.trainer import SeqLabelTrainer
+from fastNLP.loader.config_loader import ConfigLoader, ConfigSection
+from fastNLP.loader.dataset_loader import POSDatasetLoader
+from fastNLP.loader.model_loader import ModelLoader
+from fastNLP.models.sequence_modeling import SeqLabeling
+from fastNLP.saver.model_saver import ModelSaver
+
+parser = argparse.ArgumentParser()
+parser.add_argument("-s", "--save", type=str, default="./seq_label/", help="path to save pickle files")
+parser.add_argument("-t", "--train", type=str, default="../data_for_tests/people.txt",
+                    help="path to the training data")
+parser.add_argument("-c", "--config", type=str, default="../data_for_tests/config", help="path to the config file")
+parser.add_argument("-m", "--model_name", type=str, default="seq_label_model.pkl", help="the name of the model")
+parser.add_argument("-i", "--infer", type=str, default="../data_for_tests/people_infer.txt",
+                    help="data used for inference")
+
+args = parser.parse_args()
+pickle_path = args.save
+model_name = args.model_name
+config_dir = args.config
+data_path = args.train
+data_infer_path = args.infer
+
+
+def test_training():
+    # Config Loader
+    trainer_args = ConfigSection()
+    model_args = ConfigSection()
+    ConfigLoader("config.cfg").load_config(config_dir, {
+        "test_seq_label_trainer": trainer_args, "test_seq_label_model": model_args})
+
+    # Data Loader
+    pos_loader = POSDatasetLoader(data_path)
+    train_data = pos_loader.load_lines()
+
+    # Preprocessor
+    p = SeqLabelPreprocess()
+    data_train, data_dev = p.run(train_data, pickle_path=pickle_path, train_dev_split=0.5)
+    model_args["vocab_size"] = p.vocab_size
+    model_args["num_classes"] = p.num_classes
+
+    trainer = SeqLabelTrainer(
+        epochs=trainer_args["epochs"],
+        batch_size=trainer_args["batch_size"],
+        validate=False,
+        use_cuda=False,
+        pickle_path=pickle_path,
+        save_best_dev=trainer_args["save_best_dev"],
+        model_name=model_name,
+        optimizer=Optimizer("SGD", lr=0.01, momentum=0.9),
+    )
+
+    # Model
+    model = SeqLabeling(model_args)
+
+    # Start training
+    trainer.train(model, data_train, data_dev)
+
+    # Saver
+    saver = ModelSaver(os.path.join(pickle_path, model_name))
+    saver.save_pytorch(model)
+
+    del model, trainer, pos_loader
+
+    # Define the same model
+    model = SeqLabeling(model_args)
+
+    # Dump trained parameters into the model
+    ModelLoader.load_pytorch(model, os.path.join(pickle_path, model_name))
+
+    # Load test configuration
+    tester_args = ConfigSection()
+    ConfigLoader("config.cfg").load_config(config_dir, {"test_seq_label_tester": tester_args})
+
+    # Tester
+    tester = SeqLabelTester(save_output=False,
+                            save_loss=True,
+                            save_best_dev=False,
+                            batch_size=4,
+                            use_cuda=False,
+                            pickle_path=pickle_path,
+                            model_name="seq_label_in_test.pkl",
+                            print_every_step=1
+                            )
+
+    # Start testing with validation data
+    tester.test(model, data_dev)
+
+    loss, accuracy = tester.metrics
+    assert 0 < accuracy < 1