Added preliminary test scripts for sentencepiece

Other minor changes:
- Function renaming: `test_pretrain_lm` -> `test_ulmfit_default_end_to_end`
- Delete test models after completing each test.

tests/test_end_to_end.py

@@ -1,3 +1,5 @@
+import os
+import glob
 import fire
 import pytest
 
@@ -10,20 +12,43 @@
 It is a mixture of a pytest unit test and woven together to compose an end to end functional test. 
 """
 
+def delete_test_models():
+    wt2 = data / 'wiki' / 'wikitext-2'
+    imdb = data / 'imdb'
+
+    # delete test models from the pretraining step
+    for test_file in glob.iglob(f'{str(wt2)}/models/end-to-end-test*'):
+        if os.path.isfile(test_file): os.remove(test_file)
+
+    # delete test vocab and model of sentencepiece training
+    for test_file in [wt2 / 'models' / 'spm.model', 
+                      wt2 / 'models' / 'spm.vocab']:
+        if os.path.isfile(test_file): os.remove(test_file)
+
+    # delete test models from the finetuning/classifier training step
+    for test_file in glob.iglob(f'{str(imdb)}/models/end-to-end-test*'):
+        if os.path.isfile(test_file): os.remove(test_file)
+
+
 def check_data_exists():
     data = get_data_folder()
 
-    wt2 = data / "wiki" / "wikitext-2"
-    imdb = data / "imdb"
-    ensure_paths_exists(wt2 / "en.wiki.train.tokens",
-                        imdb / "train.csv",
-                        message="We don't run data preparation scripts automatically as it takes ages, run prepare_wiki-en.sh & prepare_imdb.sh")
+    wt2 = data / 'wiki' / 'wikitext-2'
+    imdb = data / 'imdb'
+    ensure_paths_exists(wt2 / 'en.wiki.train.tokens',
+                        imdb / 'train.csv',
+                        message="We don't run data preparation"
+                                " scripts automatically as it takes ages,"
+                                " run prepare_wiki-en.sh & prepare_imdb.sh")
     return imdb, wt2
 
-def test_pretrain_lm():
-    imdb,wt2 = check_data_exists()
-    lm_name="end-to-end-test-quick"
-    cuda_id=0
+
+def test_ulmfit_default_end_to_end():
+    """  Test ulmfit with (default) Moses tokenizer on small wikipedia dataset.
+    """
+    imdb, wt2 = check_data_exists()
+    lm_name = 'end-to-end-test-default'
+    cuda_id = 0
     results = ulmfit.pretrain_lm.pretrain_lm(
         dir_path=wt2,
         lang='en',
@@ -48,3 +73,31 @@ def test_pretrain_lm():
                 bs=20, bptt=70, name=lm_name+'-imdb-clas',
                 dataset='imdb',
                 ds_pct=0.03)
+
+    delete_test_models()
+
+
+def test_ulmfit_sentencepiece_end_to_end():
+    """ Test ulmfit with sentencepiece tokenizer on small wikipedia dataset.
+    """
+    imdb, wt2 = check_data_exists()
+    lm_name = 'end-to-end-test-spm'
+    cuda_id = 0
+    results = ulmfit.pretrain_lm.pretrain_lm(
+        dir_path=wt2,
+        lang='en',
+        cuda_id=cuda_id,
+        qrnn=True,
+        subword=True,
+        max_vocab=1000,
+        bs=80,
+        num_epochs=1,
+        name=lm_name,
+    )
+
+    assert results['accuracy'] > 0.30
+
+    # NOTE: ds_pct is not available for sentencepiece -- tests are on the complete dataset
+    #       sentencepiece for finetuning/classification is currently not implemented
+
+    delete_test_models()