Add runner unit tests. (#68)

* add runner unit tests

* update

* update

* add test custom loop and hook

* add test model wrapper

* add test setup env

* fix typo

* fix launcher

* fix typo

* test default scope

* add logger test

* fix dataloader

* add test loop

* resolve comments

* resolve comments

tests/test_runner/test_loop.py

+# Copyright (c) OpenMMLab. All rights reserved.
+from unittest import TestCase
+from unittest.mock import Mock
+
+import numpy as np
+import torch
+from torch.utils.data import DataLoader, Dataset
+
+from mmengine.runner.loop import (EpochBasedTrainLoop, IterBasedTrainLoop,
+                                  TestLoop, ValLoop)
+
+
+class ToyDataset(Dataset):
+    META = dict()  # type: ignore
+    data = np.zeros((30, 1, 1, 1))
+
+    def __len__(self):
+        return self.data.shape[0]
+
+    def __getitem__(self, index):
+        return torch.from_numpy(self.data[index])
+
+
+class TestLoops(TestCase):
+
+    def setUp(self) -> None:
+        self.runner = Mock()
+        self.runner.call_hooks = Mock()
+        self.runner.model = Mock()
+        self.runner.epoch = 0
+        self.runner.iter = 0
+        self.runner.inner_iter = 0
+        self.runner.model.train_step = Mock()
+        self.runner.model.val_step = Mock()
+
+        self.evaluator = Mock()
+        self.evaluator.process = Mock()
+        self.evaluator.evaluate = Mock()
+
+    def test_epoch_based_train_loop(self):
+        train_loop = EpochBasedTrainLoop(
+            runner=self.runner, loader=DataLoader(ToyDataset()), max_epoch=3)
+        train_loop.run()
+        assert train_loop.runner.epoch == 3
+        assert train_loop.runner.iter == 90
+
+    def test_iter_based_train_loop(self):
+        train_loop = IterBasedTrainLoop(
+            runner=self.runner, loader=DataLoader(ToyDataset()), max_iter=25)
+        train_loop.run()
+        assert train_loop.runner.epoch == 0
+        assert train_loop.runner.iter == 25
+
+    def test_val_loop(self):
+        val_loop = ValLoop(
+            runner=self.runner,
+            loader=DataLoader(ToyDataset()),
+            evaluator=self.evaluator)
+        val_loop.run()
+
+    def test_test_loop(self):
+        test_loop = TestLoop(
+            runner=self.runner,
+            loader=DataLoader(ToyDataset()),
+            evaluator=self.evaluator)
+        test_loop.run()