Update test_tracker (Lightning-AI#1409)

* Add test configuration for test_tracker with a `MetricTracker` of `MultioutputWrapper`
* Change the test to support the case where the values returned by `MetricTracker` are lists

tests/unittests/wrappers/test_tracker.py

@@ -22,7 +22,7 @@
     MulticlassPrecision,
     MulticlassRecall,
 )
-from torchmetrics.wrappers import MetricTracker
+from torchmetrics.wrappers import MetricTracker, MultioutputWrapper
 from unittests.helpers import seed_all
 
 seed_all(42)
@@ -95,6 +95,11 @@ def test_raises_error_if_increment_not_called(method, method_input):
             (torch.randn(50), torch.randn(50)),
             [False, False],
         ),
+        (
+            MultioutputWrapper(MeanSquaredError(), num_outputs=2),
+            (torch.randn(50, 2), torch.randn(50, 2)),
+            [False, False],
+        ),
     ],
 )
 def test_tracker(base_metric, metric_input, maximize):
@@ -113,6 +118,9 @@ def test_tracker(base_metric, metric_input, maximize):
         if isinstance(val, dict):
             for v in val.values():
                 assert v != 0.0
+        elif isinstance(val, list):
+            for v in val:
+                assert v != 0.0
         else:
             assert val != 0.0
         assert tracker.n_steps == i + 1
@@ -123,6 +131,9 @@ def test_tracker(base_metric, metric_input, maximize):
     if isinstance(all_computed_val, dict):
         for v in all_computed_val.values():
             assert v.numel() == 5
+    elif isinstance(all_computed_val, list):
+        for v in all_computed_val:
+            assert v.numel() == 5
     else:
         assert all_computed_val.numel() == 5
 
@@ -132,6 +143,10 @@ def test_tracker(base_metric, metric_input, maximize):
         for v, i in zip(val.values(), idx.values()):
             assert v != 0.0
             assert i in list(range(5))
+    elif isinstance(val, list):
+        for v, i in zip(val, idx):
+            assert v != 0.0
+            assert i in list(range(5))
     else:
         assert val != 0.0
         assert idx in list(range(5))