add testing code in stack embedding

test/embeddings/test_stack_embeddings.py

@@ -0,0 +1,20 @@
+import unittest
+
+import torch
+
+from fastNLP import Vocabulary, DataSet, Instance
+from fastNLP.embeddings import LSTMCharEmbedding, CNNCharEmbedding, StackEmbedding
+
+
+class TestCharEmbed(unittest.TestCase):
+    def test_case_1(self):
+        ds = DataSet([Instance(words=['hello', 'world']), Instance(words=['hello', 'Jack'])])
+        vocab = Vocabulary().from_dataset(ds, field_name='words')
+        self.assertEqual(len(vocab), 5)
+        cnn_embed = CNNCharEmbedding(vocab, embed_size=60)
+        lstm_embed = LSTMCharEmbedding(vocab, embed_size=70)
+        embed = StackEmbedding([cnn_embed, lstm_embed])
+        x = torch.LongTensor([[2, 1, 0], [4, 3, 4]])
+        y = embed(x)
+        self.assertEqual(tuple(y.size()), (2, 3, 130))
+