Add unittest in test_build_dataset

tests/test_data/test_dataset_builder.py

@@ -6,8 +6,8 @@
 from torch.utils.data import (DistributedSampler, RandomSampler,
                               SequentialSampler)
 
-from mmseg.datasets import (DATASETS, ConcatDataset, build_dataloader,
-                            build_dataset)
+from mmseg.datasets import (DATASETS, ConcatDataset, MultiImageMixDataset,
+                            build_dataloader, build_dataset)
 
 
 @DATASETS.register_module()
@@ -48,6 +48,11 @@ def test_build_dataset():
     assert isinstance(dataset, ConcatDataset)
     assert len(dataset) == 10
 
+    cfg = dict(type='MultiImageMixDataset', dataset=cfg, pipeline=[])
+    dataset = build_dataset(cfg)
+    assert isinstance(dataset, MultiImageMixDataset)
+    assert len(dataset) == 10
+
     # with ann_dir, split
     cfg = dict(
         type='CustomDataset',