diff --git a/.coveragerc b/.coveragerc
new file mode 100644
index 000000000..d4a7a6d63
--- /dev/null
+++ b/.coveragerc
@@ -0,0 +1,11 @@
+[run]
+omit =
+    # avoid measuring strange non-existing files
+    /workspace/config.py
+    /workspace/config-3.py
+
+    # avoid measuring third-party dist packages
+    */dist-packages/*
+
+    # avoid measuring code of unittest
+    tests/*
diff --git a/data_juicer/ops/mapper/remove_table_text_mapper.py b/data_juicer/ops/mapper/remove_table_text_mapper.py
index ff2b07a4f..87b06e5d1 100644
--- a/data_juicer/ops/mapper/remove_table_text_mapper.py
+++ b/data_juicer/ops/mapper/remove_table_text_mapper.py
@@ -36,8 +36,8 @@ def __init__(self,
 
     def process_batched(self, samples):
         for idx, text in enumerate(samples[self.text_key]):
-            for idx in range(self.min_col - 1, self.max_col):
-                pattern = re.compile(self.pattern % idx)
+            for i in range(self.min_col - 1, self.max_col):
+                pattern = re.compile(self.pattern % i)
                 text = pattern.sub('', text)
 
             samples[self.text_key][idx] = text
diff --git a/data_juicer/utils/model_utils.py b/data_juicer/utils/model_utils.py
index cda046b81..dc593bc7f 100644
--- a/data_juicer/utils/model_utils.py
+++ b/data_juicer/utils/model_utils.py
@@ -612,7 +612,8 @@ def prepare_model(model_type, **model_kwargs):
     model_func = MODEL_FUNCTION_MAPPING[model_type]
     model_key = partial(model_func, **model_kwargs)
     # always instantiate once for possible caching
-    model_key()
+    if model_type != 'vllm':
+        model_key()
     return model_key
 
 
diff --git a/data_juicer/utils/unittest_utils.py b/data_juicer/utils/unittest_utils.py
index 81033b224..1e66c55cc 100644
--- a/data_juicer/utils/unittest_utils.py
+++ b/data_juicer/utils/unittest_utils.py
@@ -16,6 +16,8 @@
 
 SKIPPED_TESTS = Registry('SkippedTests')
 
+CLEAR_MODEL = False
+
 
 def TEST_TAG(*tags):
     """Tags for test case.
@@ -29,6 +31,15 @@ def decorator(func):
     return decorator
 
 
+def set_clear_model_flag(flag):
+    global CLEAR_MODEL
+    CLEAR_MODEL = flag
+    if CLEAR_MODEL:
+        print('CLEAR DOWNLOADED MODELS AFTER UNITTESTS.')
+    else:
+        print('KEEP DOWNLOADED MODELS AFTER UNITTESTS.')
+
+
 class DataJuicerTestCaseBase(unittest.TestCase):
 
     @classmethod
@@ -48,7 +59,9 @@ def tearDownClass(cls, hf_model_name=None) -> None:
         multiprocess.set_start_method(cls.original_mp_method, force=True)
 
         # clean the huggingface model cache files
-        if hf_model_name:
+        if not CLEAR_MODEL:
+            pass
+        elif hf_model_name:
             # given the hf model name, remove this model only
             model_dir = os.path.join(
                 transformers.TRANSFORMERS_CACHE,
diff --git a/environments/dev_requires.txt b/environments/dev_requires.txt
index ff091a304..9793d5746 100644
--- a/environments/dev_requires.txt
+++ b/environments/dev_requires.txt
@@ -1,3 +1,4 @@
+coverage
 pre-commit
 sphinx
 sphinx-autobuild
diff --git a/tests/core/test_monitor.py b/tests/core/test_monitor.py
index 01840348d..3f7a35f21 100644
--- a/tests/core/test_monitor.py
+++ b/tests/core/test_monitor.py
@@ -4,6 +4,8 @@
 from data_juicer.core import Monitor
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
+# Skip this test due to some random resource utilization fluctuation, which may
+# cause failure of this test
 @SKIPPED_TESTS.register_module()
 class MonitorTest(DataJuicerTestCaseBase):
 
diff --git a/tests/ops/filter/test_image_aesthetics_filter.py b/tests/ops/filter/test_image_aesthetics_filter.py
index e20f9d2c6..3ebb8419c 100644
--- a/tests/ops/filter/test_image_aesthetics_filter.py
+++ b/tests/ops/filter/test_image_aesthetics_filter.py
@@ -8,7 +8,6 @@
 from data_juicer.utils.constant import Fields
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
-@SKIPPED_TESTS.register_module()
 class ImageAestheticsFilterTest(DataJuicerTestCaseBase):
 
     maxDiff = None
diff --git a/tests/ops/filter/test_image_face_count_filter.py b/tests/ops/filter/test_image_face_count_filter.py
index dd106f6bb..becb47148 100644
--- a/tests/ops/filter/test_image_face_count_filter.py
+++ b/tests/ops/filter/test_image_face_count_filter.py
@@ -8,7 +8,6 @@
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
 
-@SKIPPED_TESTS.register_module()
 class ImageFaceCountFilterTest(DataJuicerTestCaseBase):
 
     data_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..',
diff --git a/tests/ops/filter/test_image_face_ratio_filter.py b/tests/ops/filter/test_image_face_ratio_filter.py
index d82ac2ec1..69a10a42d 100644
--- a/tests/ops/filter/test_image_face_ratio_filter.py
+++ b/tests/ops/filter/test_image_face_ratio_filter.py
@@ -8,7 +8,6 @@
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
 
-@SKIPPED_TESTS.register_module()
 class ImageFaceRatioFilterTest(DataJuicerTestCaseBase):
 
     maxDiff = None
diff --git a/tests/ops/filter/test_image_nsfw_filter.py b/tests/ops/filter/test_image_nsfw_filter.py
index 0a588e272..87f24e94b 100644
--- a/tests/ops/filter/test_image_nsfw_filter.py
+++ b/tests/ops/filter/test_image_nsfw_filter.py
@@ -10,7 +10,6 @@
 from data_juicer.utils.constant import Fields
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
-@SKIPPED_TESTS.register_module()
 class ImageNSFWFilterTest(DataJuicerTestCaseBase):
 
     data_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..',
diff --git a/tests/ops/filter/test_image_text_matching_filter.py b/tests/ops/filter/test_image_text_matching_filter.py
index 0551da254..91ed938df 100644
--- a/tests/ops/filter/test_image_text_matching_filter.py
+++ b/tests/ops/filter/test_image_text_matching_filter.py
@@ -11,7 +11,6 @@
 from data_juicer.utils.mm_utils import SpecialTokens
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
-@SKIPPED_TESTS.register_module()
 class ImageTextMatchingFilterTest(DataJuicerTestCaseBase):
 
     data_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..',
diff --git a/tests/ops/filter/test_image_watermark_filter.py b/tests/ops/filter/test_image_watermark_filter.py
index 01ed2e0dc..b5e5146f8 100644
--- a/tests/ops/filter/test_image_watermark_filter.py
+++ b/tests/ops/filter/test_image_watermark_filter.py
@@ -10,7 +10,6 @@
 from data_juicer.utils.constant import Fields
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
-@SKIPPED_TESTS.register_module()
 class ImageWatermarkFilterTest(DataJuicerTestCaseBase):
 
     data_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..',
diff --git a/tests/ops/filter/test_phrase_grounding_recall_filter.py b/tests/ops/filter/test_phrase_grounding_recall_filter.py
index e865c2f22..201e71214 100644
--- a/tests/ops/filter/test_phrase_grounding_recall_filter.py
+++ b/tests/ops/filter/test_phrase_grounding_recall_filter.py
@@ -11,7 +11,6 @@
 from data_juicer.utils.mm_utils import SpecialTokens
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
-@SKIPPED_TESTS.register_module()
 class PhraseGroundingRecallFilterTest(DataJuicerTestCaseBase):
 
     data_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..',
diff --git a/tests/ops/filter/test_video_aesthetics_filter.py b/tests/ops/filter/test_video_aesthetics_filter.py
index 551d0e721..b0681ef4d 100644
--- a/tests/ops/filter/test_video_aesthetics_filter.py
+++ b/tests/ops/filter/test_video_aesthetics_filter.py
@@ -9,7 +9,6 @@
 from data_juicer.utils.mm_utils import SpecialTokens
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
-@SKIPPED_TESTS.register_module()
 class VideoAestheticsFilterTest(DataJuicerTestCaseBase):
 
     data_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..',
diff --git a/tests/ops/filter/test_video_nsfw_filter.py b/tests/ops/filter/test_video_nsfw_filter.py
index 3c713407d..8376eb7af 100644
--- a/tests/ops/filter/test_video_nsfw_filter.py
+++ b/tests/ops/filter/test_video_nsfw_filter.py
@@ -10,7 +10,6 @@
 from data_juicer.utils.constant import Fields
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
-@SKIPPED_TESTS.register_module()
 class VideoNSFWFilterTest(DataJuicerTestCaseBase):
 
     data_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..',
diff --git a/tests/ops/filter/test_video_ocr_area_ratio_filter.py b/tests/ops/filter/test_video_ocr_area_ratio_filter.py
index 9884ab1cf..b7c7e6f50 100644
--- a/tests/ops/filter/test_video_ocr_area_ratio_filter.py
+++ b/tests/ops/filter/test_video_ocr_area_ratio_filter.py
@@ -8,7 +8,6 @@
 from data_juicer.utils.constant import Fields
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
-@SKIPPED_TESTS.register_module()
 class VideoOcrAreaRatioFilterTest(DataJuicerTestCaseBase):
 
     data_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..',
diff --git a/tests/ops/filter/test_video_tagging_from_frames_filter.py b/tests/ops/filter/test_video_tagging_from_frames_filter.py
index c16b07d4d..545be9748 100644
--- a/tests/ops/filter/test_video_tagging_from_frames_filter.py
+++ b/tests/ops/filter/test_video_tagging_from_frames_filter.py
@@ -8,7 +8,6 @@
 from data_juicer.utils.mm_utils import SpecialTokens
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
-@SKIPPED_TESTS.register_module()
 class VideoTaggingFromFramesFilterTest(DataJuicerTestCaseBase):
     data_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..',
                              'data')
diff --git a/tests/ops/filter/test_video_watermark_filter.py b/tests/ops/filter/test_video_watermark_filter.py
index aca75131f..629319e3f 100644
--- a/tests/ops/filter/test_video_watermark_filter.py
+++ b/tests/ops/filter/test_video_watermark_filter.py
@@ -10,7 +10,6 @@
 from data_juicer.utils.constant import Fields
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
-@SKIPPED_TESTS.register_module()
 class VideoWatermarkFilterTest(DataJuicerTestCaseBase):
 
     data_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..',
diff --git a/tests/ops/mapper/test_extract_qa_mapper.py b/tests/ops/mapper/test_extract_qa_mapper.py
index 2e1b59a78..415efad4e 100644
--- a/tests/ops/mapper/test_extract_qa_mapper.py
+++ b/tests/ops/mapper/test_extract_qa_mapper.py
@@ -4,7 +4,7 @@
 from data_juicer.utils.unittest_utils import (SKIPPED_TESTS,
                                               DataJuicerTestCaseBase)
 
-# Skip tests for this OP in the GitHub actions due to disk space limitation.
+# Skip tests for this OP in the GitHub actions due to unknown DistNetworkError.
 # These tests have been tested locally.
 @SKIPPED_TESTS.register_module()
 class ExtractQAMapperTest(DataJuicerTestCaseBase):
diff --git a/tests/ops/mapper/test_generate_instruction_mapper.py b/tests/ops/mapper/test_generate_instruction_mapper.py
index 43bd31262..a250fbcc4 100644
--- a/tests/ops/mapper/test_generate_instruction_mapper.py
+++ b/tests/ops/mapper/test_generate_instruction_mapper.py
@@ -4,7 +4,7 @@
 from data_juicer.utils.unittest_utils import (SKIPPED_TESTS,
                                               DataJuicerTestCaseBase)
 
-# Skip tests for this OP in the GitHub actions due to disk space limitation.
+# Skip tests for this OP in the GitHub actions due to unknown DistNetworkError.
 # These tests have been tested locally.
 @SKIPPED_TESTS.register_module()
 class GenerateInstructionMapperTest(DataJuicerTestCaseBase):
diff --git a/tests/ops/mapper/test_image_captioning_mapper.py b/tests/ops/mapper/test_image_captioning_mapper.py
index c4c3d1e3e..2a772ab20 100644
--- a/tests/ops/mapper/test_image_captioning_mapper.py
+++ b/tests/ops/mapper/test_image_captioning_mapper.py
@@ -9,7 +9,7 @@
                                               DataJuicerTestCaseBase)
 
 
-# Skip tests for this OP in the GitHub actions due to disk space limitation.
+# Skip tests for this OP in the GitHub actions due to OOM on the current runner
 # These tests have been tested locally.
 @SKIPPED_TESTS.register_module()
 class ImageCaptioningMapperTest(DataJuicerTestCaseBase):
diff --git a/tests/ops/mapper/test_image_diffusion_mapper.py b/tests/ops/mapper/test_image_diffusion_mapper.py
index ad241732f..5883a7ff7 100644
--- a/tests/ops/mapper/test_image_diffusion_mapper.py
+++ b/tests/ops/mapper/test_image_diffusion_mapper.py
@@ -10,7 +10,7 @@
                                               DataJuicerTestCaseBase)
 
 
-# Skip tests for this OP in the GitHub actions due to disk space limitation.
+# Skip tests for this OP in the GitHub actions due to OOM on the current runner
 # These tests have been tested locally.
 @SKIPPED_TESTS.register_module()
 class ImageDiffusionMapperTest(DataJuicerTestCaseBase):
diff --git a/tests/ops/mapper/test_image_tagging_mapper.py b/tests/ops/mapper/test_image_tagging_mapper.py
index e9609b12f..06fd6fba7 100644
--- a/tests/ops/mapper/test_image_tagging_mapper.py
+++ b/tests/ops/mapper/test_image_tagging_mapper.py
@@ -8,6 +8,8 @@
 from data_juicer.utils.constant import Fields
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
+# Skip tests for this OP in the GitHub actions due to OOM on the current runner
+# These tests have been tested locally.
 @SKIPPED_TESTS.register_module()
 class ImageTaggingMapperTest(DataJuicerTestCaseBase):
     data_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..',
diff --git a/tests/ops/mapper/test_nlpcda_zh_mapper.py b/tests/ops/mapper/test_nlpcda_zh_mapper.py
index 3624a9c35..ce21ea55d 100644
--- a/tests/ops/mapper/test_nlpcda_zh_mapper.py
+++ b/tests/ops/mapper/test_nlpcda_zh_mapper.py
@@ -4,9 +4,12 @@
 
 from data_juicer.core import NestedDataset as Dataset
 from data_juicer.ops.mapper.nlpcda_zh_mapper import NlpcdaZhMapper
-from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase
+from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
 
+# Skip tests for this OP in the GitHub actions due to unknown UnicodeEncodeError
+# These tests have been tested locally.
+@SKIPPED_TESTS.register_module()
 class NlpaugEnMapperTest(DataJuicerTestCaseBase):
 
     def setUp(self):
diff --git a/tests/ops/mapper/test_optimize_instruction_mapper.py b/tests/ops/mapper/test_optimize_instruction_mapper.py
index 7c7b58b4c..4b3e4562b 100644
--- a/tests/ops/mapper/test_optimize_instruction_mapper.py
+++ b/tests/ops/mapper/test_optimize_instruction_mapper.py
@@ -3,7 +3,7 @@
 from data_juicer.utils.unittest_utils import (SKIPPED_TESTS,
                                               DataJuicerTestCaseBase)
 
-# Skip tests for this OP in the GitHub actions due to disk space limitation.
+# Skip tests for this OP in the GitHub actions due to unknown DistNetworkError.
 # These tests have been tested locally.
 @SKIPPED_TESTS.register_module()
 class OptimizeInstructionMapperTest(DataJuicerTestCaseBase):
diff --git a/tests/ops/mapper/test_video_captioning_from_audio_mapper.py b/tests/ops/mapper/test_video_captioning_from_audio_mapper.py
index caadeb97b..402509639 100644
--- a/tests/ops/mapper/test_video_captioning_from_audio_mapper.py
+++ b/tests/ops/mapper/test_video_captioning_from_audio_mapper.py
@@ -9,7 +9,7 @@
                                               DataJuicerTestCaseBase)
 
 
-# Skip tests for this OP in the GitHub actions due to disk space limitation.
+# Skip tests for this OP in the GitHub actions due to OOM on the current runner
 # These tests have been tested locally.
 @SKIPPED_TESTS.register_module()
 class VideoCaptioningFromAudioMapperTest(DataJuicerTestCaseBase):
diff --git a/tests/ops/mapper/test_video_captioning_from_frames_mapper.py b/tests/ops/mapper/test_video_captioning_from_frames_mapper.py
index 71bf963f6..d9bf29724 100644
--- a/tests/ops/mapper/test_video_captioning_from_frames_mapper.py
+++ b/tests/ops/mapper/test_video_captioning_from_frames_mapper.py
@@ -9,7 +9,7 @@
                                               DataJuicerTestCaseBase)
 
 
-# Skip tests for this OP in the GitHub actions due to disk space limitation.
+# Skip tests for this OP in the GitHub actions due to OOM on the current runner
 # These tests have been tested locally.
 @SKIPPED_TESTS.register_module()
 class VideoCaptioningFromFramesMapperTest(DataJuicerTestCaseBase):
diff --git a/tests/ops/mapper/test_video_captioning_from_summarizer_mapper.py b/tests/ops/mapper/test_video_captioning_from_summarizer_mapper.py
index 79f8037b9..016a4d73b 100644
--- a/tests/ops/mapper/test_video_captioning_from_summarizer_mapper.py
+++ b/tests/ops/mapper/test_video_captioning_from_summarizer_mapper.py
@@ -9,7 +9,7 @@
                                               DataJuicerTestCaseBase)
 
 
-# Skip tests for this OP in the GitHub actions due to disk space limitation.
+# Skip tests for this OP in the GitHub actions due to OOM on the current runner
 # These tests have been tested locally.
 @SKIPPED_TESTS.register_module()
 class VideoCaptioningFromSummarizerMapperTest(DataJuicerTestCaseBase):
diff --git a/tests/ops/mapper/test_video_captioning_from_video_mapper.py b/tests/ops/mapper/test_video_captioning_from_video_mapper.py
index 012761af5..f3de27226 100644
--- a/tests/ops/mapper/test_video_captioning_from_video_mapper.py
+++ b/tests/ops/mapper/test_video_captioning_from_video_mapper.py
@@ -9,7 +9,7 @@
                                               DataJuicerTestCaseBase)
 
 
-# Skip tests for this OP in the GitHub actions due to disk space limitation.
+# Skip tests for this OP in the GitHub actions due to OOM on the current runner
 # These tests have been tested locally.
 @SKIPPED_TESTS.register_module()
 class VideoCaptioningFromVideoMapperTest(DataJuicerTestCaseBase):
diff --git a/tests/ops/mapper/test_video_remove_watermark_mapper.py b/tests/ops/mapper/test_video_remove_watermark_mapper.py
index 0cfefa76f..96231a976 100644
--- a/tests/ops/mapper/test_video_remove_watermark_mapper.py
+++ b/tests/ops/mapper/test_video_remove_watermark_mapper.py
@@ -11,7 +11,6 @@
                                               DataJuicerTestCaseBase)
 
 
-@SKIPPED_TESTS.register_module()
 class VideoRemoveWatermarkMapperTest(DataJuicerTestCaseBase):
 
     data_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..',
diff --git a/tests/ops/mapper/test_video_split_by_scene_mapper.py b/tests/ops/mapper/test_video_split_by_scene_mapper.py
index dbbc32553..6e71789e6 100644
--- a/tests/ops/mapper/test_video_split_by_scene_mapper.py
+++ b/tests/ops/mapper/test_video_split_by_scene_mapper.py
@@ -8,7 +8,6 @@
 from data_juicer.utils.mm_utils import SpecialTokens
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
-@SKIPPED_TESTS.register_module()
 class VideoSplitBySceneMapperTest(DataJuicerTestCaseBase):
 
     data_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..',
diff --git a/tests/ops/mapper/test_video_tagging_from_frames_mapper.py b/tests/ops/mapper/test_video_tagging_from_frames_mapper.py
index b310591a4..4484df754 100644
--- a/tests/ops/mapper/test_video_tagging_from_frames_mapper.py
+++ b/tests/ops/mapper/test_video_tagging_from_frames_mapper.py
@@ -9,6 +9,8 @@
 from data_juicer.utils.mm_utils import SpecialTokens
 from data_juicer.utils.unittest_utils import DataJuicerTestCaseBase, SKIPPED_TESTS
 
+# Skip tests for this OP in the GitHub actions due to OOM on the current runner
+# These tests have been tested locally.
 @SKIPPED_TESTS.register_module()
 class VideoTaggingFromFramesMapperTest(DataJuicerTestCaseBase):
     data_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..',
diff --git a/tests/ops/test_op_fusion.py b/tests/ops/test_op_fusion.py
index d545e0074..271737154 100644
--- a/tests/ops/test_op_fusion.py
+++ b/tests/ops/test_op_fusion.py
@@ -5,7 +5,6 @@
                                               DataJuicerTestCaseBase)
 
 
-@SKIPPED_TESTS.register_module()
 class OpFusionTest(DataJuicerTestCaseBase):
 
     def _run_op_fusion(self, original_process_list, target_process_list):
diff --git a/tests/run.py b/tests/run.py
index 3b7b99736..378d6b0d6 100644
--- a/tests/run.py
+++ b/tests/run.py
@@ -10,10 +10,11 @@
 import os
 import sys
 import unittest
+import coverage
 
 from loguru import logger
 
-from data_juicer.utils.unittest_utils import SKIPPED_TESTS
+from data_juicer.utils.unittest_utils import SKIPPED_TESTS, set_clear_model_flag
 
 file_dir = os.path.join(os.path.dirname(__file__), '..')
 sys.path.append(file_dir)
@@ -26,8 +27,14 @@
 parser.add_argument('--test_dir',
                     default='tests',
                     help='directory to be tested')
+parser.add_argument('--clear_model',
+                    default=False,
+                    type=bool,
+                    help='whether to clear the downloaded models for tests. '
+                         'It\'s False in default.')
 args = parser.parse_args()
 
+set_clear_model_flag(args.clear_model)
 
 class TaggedTestLoader(unittest.TestLoader):
     def __init__(self, tag="standalone"):
@@ -66,13 +73,21 @@ def gather_test_cases(test_dir, pattern, tag):
 
 
 def main():
+    cov = coverage.Coverage()
+    cov.start()
+
     runner = unittest.TextTestRunner()
     test_suite = gather_test_cases(os.path.abspath(args.test_dir),
                                    args.pattern, args.tag)
     res = runner.run(test_suite)
+
+    cov.stop()
+
     if not res.wasSuccessful():
         exit(1)
 
+    cov.report()
+
 
 if __name__ == '__main__':
     main()