Fix test interactions (#18994)

(cherry picked from commit 340961a)

Author: awaelchli

tests/tests_fabric/loggers/test_tensorboard.py

@@ -214,10 +214,10 @@ def test_tensorboard_finalize(monkeypatch, tmp_path):
 
 
 @mock.patch("lightning.fabric.loggers.tensorboard.log")
-def test_tensorboard_with_symlink(log, tmp_path):
+def test_tensorboard_with_symlink(log, tmp_path, monkeypatch):
     """Tests a specific failure case when tensorboard logger is used with empty name, symbolic link ``save_dir``, and
     relative paths."""
-    os.chdir(tmp_path)  # need to use relative paths
+    monkeypatch.chdir(tmp_path)  # need to use relative paths
     source = os.path.join(".", "lightning_logs")
     dest = os.path.join(".", "sym_lightning_logs")
 

tests/tests_pytorch/checkpointing/test_model_checkpoint.py

@@ -401,7 +401,7 @@ def test_model_checkpoint_no_extraneous_invocations(tmpdir):
     assert trainer.state.finished, f"Training failed with {trainer.state}"
 
 
-def test_model_checkpoint_format_checkpoint_name(tmpdir):
+def test_model_checkpoint_format_checkpoint_name(tmpdir, monkeypatch):
     # empty filename:
     ckpt_name = ModelCheckpoint._format_checkpoint_name("", {"epoch": 3, "step": 2})
     assert ckpt_name == "epoch=3-step=2"
@@ -422,18 +422,16 @@ def test_model_checkpoint_format_checkpoint_name(tmpdir):
     assert ckpt_name == "epoch=003-epoch_test=003"
 
     # prefix
-    char_org = ModelCheckpoint.CHECKPOINT_JOIN_CHAR
-    ModelCheckpoint.CHECKPOINT_JOIN_CHAR = "@"
+    monkeypatch.setattr(ModelCheckpoint, "CHECKPOINT_JOIN_CHAR", "@")
     ckpt_name = ModelCheckpoint._format_checkpoint_name("{epoch},{acc:.5f}", {"epoch": 3, "acc": 0.03}, prefix="test")
     assert ckpt_name == "test@epoch=3,acc=0.03000"
-    ModelCheckpoint.CHECKPOINT_JOIN_CHAR = char_org
+    monkeypatch.undo()
 
     # non-default char for equals sign
-    default_char = ModelCheckpoint.CHECKPOINT_EQUALS_CHAR
-    ModelCheckpoint.CHECKPOINT_EQUALS_CHAR = ":"
+    monkeypatch.setattr(ModelCheckpoint, "CHECKPOINT_EQUALS_CHAR", ":")
     ckpt_name = ModelCheckpoint._format_checkpoint_name("{epoch:03d}-{acc}", {"epoch": 3, "acc": 0.03})
     assert ckpt_name == "epoch:003-acc:0.03"
-    ModelCheckpoint.CHECKPOINT_EQUALS_CHAR = default_char
+    monkeypatch.undo()
 
     # no dirpath set
     ckpt_name = ModelCheckpoint(monitor="early_stop_on", dirpath=None).format_checkpoint_name({"epoch": 3, "step": 2})

tests/tests_pytorch/loggers/test_tensorboard.py

@@ -313,10 +313,10 @@ def test_tensorboard_save_hparams_to_yaml_once(tmp_path):
 
 
 @mock.patch("lightning.pytorch.loggers.tensorboard.log")
-def test_tensorboard_with_symlink(log, tmp_path):
+def test_tensorboard_with_symlink(log, tmp_path, monkeypatch):
     """Tests a specific failure case when tensorboard logger is used with empty name, symbolic link ``save_dir``, and
     relative paths."""
-    os.chdir(tmp_path)  # need to use relative paths
+    monkeypatch.chdir(tmp_path)  # need to use relative paths
     source = os.path.join(".", "lightning_logs")
     dest = os.path.join(".", "sym_lightning_logs")