Enhance displaying and debuggability in dump comparator (#19466)

test/registered/debug_utils/comparator/test_dump_loader.py

@@ -0,0 +1,62 @@
+import sys
+from pathlib import Path
+
+import pytest
+import torch
+
+from sglang.srt.debug_utils.dump_loader import read_tokenizer_path
+from sglang.test.ci.ci_register import register_cpu_ci
+
+register_cpu_ci(est_time=10, suite="default", nightly=True)
+
+
+def _save_pt(
+    directory: Path, filename: str, *, value: torch.Tensor, meta: dict
+) -> None:
+    torch.save({"value": value, "meta": meta}, directory / filename)
+
+
+class TestReadTokenizerPath:
+    def test_finds_tokenizer_path(self, tmp_path: Path) -> None:
+        _save_pt(
+            tmp_path,
+            "name=x___step=0___rank=0___dump_index=0.pt",
+            value=torch.tensor([1.0]),
+            meta={"tokenizer_path": "/models/llama-3"},
+        )
+        result = read_tokenizer_path(tmp_path)
+        assert result == "/models/llama-3"
+
+    def test_returns_none_when_no_tokenizer_path(self, tmp_path: Path) -> None:
+        _save_pt(
+            tmp_path,
+            "name=x___step=0___rank=0___dump_index=0.pt",
+            value=torch.tensor([1.0]),
+            meta={},
+        )
+        result = read_tokenizer_path(tmp_path)
+        assert result is None
+
+    def test_returns_none_for_empty_directory(self, tmp_path: Path) -> None:
+        result = read_tokenizer_path(tmp_path)
+        assert result is None
+
+    def test_skips_files_without_tokenizer_path(self, tmp_path: Path) -> None:
+        _save_pt(
+            tmp_path,
+            "name=a___step=0___rank=0___dump_index=0.pt",
+            value=torch.tensor([1.0]),
+            meta={},
+        )
+        _save_pt(
+            tmp_path,
+            "name=b___step=0___rank=0___dump_index=1.pt",
+            value=torch.tensor([2.0]),
+            meta={"tokenizer_path": "/models/deepseek"},
+        )
+        result = read_tokenizer_path(tmp_path)
+        assert result == "/models/deepseek"
+
+
+if __name__ == "__main__":
+    sys.exit(pytest.main([__file__]))