diff --git a/tests/unit/test_files_checks.py b/tests/unit/test_files_checks.py
index 37c698d2..68af1f6c 100644
--- a/tests/unit/test_files_checks.py
+++ b/tests/unit/test_files_checks.py
@@ -303,3 +303,92 @@ def test_check_jsonl_empty_messages(tmp_path: Path):
     assert (
         "Expected a non-empty list of messages. Found empty list" in report["message"]
     )
+
+
+def test_check_jsonl_valid_weights_all_messages(tmp_path: Path):
+    file = tmp_path / "valid_weights_all.jsonl"
+    content = [
+        {
+            "messages": [
+                {"role": "user", "content": "Hello", "weight": 1},
+                {"role": "assistant", "content": "Hi there!", "weight": 0},
+                {"role": "user", "content": "How are you?", "weight": 1},
+                {"role": "assistant", "content": "I'm doing well!", "weight": 1},
+            ]
+        },
+        {
+            "messages": [
+                {"role": "system", "content": "You are helpful", "weight": 0},
+                {"role": "user", "content": "What's the weather?", "weight": 1},
+                {"role": "assistant", "content": "It's sunny today!", "weight": 1},
+            ]
+        },
+    ]
+    with file.open("w") as f:
+        f.write("\n".join(json.dumps(item) for item in content))
+
+    report = check_file(file)
+    assert report["is_check_passed"]
+    assert report["num_samples"] == len(content)
+
+
+def test_check_jsonl_valid_weights_mixed_with_none(tmp_path: Path):
+    file = tmp_path / "valid_weights_mixed.jsonl"
+    content = [
+        {
+            "messages": [
+                {"role": "user", "content": "Hello", "weight": 1},
+                {"role": "assistant", "content": "Hi there!", "weight": 0},
+                {"role": "user", "content": "How are you?"},
+                {"role": "assistant", "content": "I'm doing well!"},
+            ]
+        },
+        {
+            "messages": [
+                {"role": "user", "content": "What's the weather?"},
+                {"role": "assistant", "content": "It's sunny today!"},
+            ]
+        },
+    ]
+    with file.open("w") as f:
+        f.write("\n".join(json.dumps(item) for item in content))
+
+    report = check_file(file)
+    assert report["is_check_passed"]
+    assert report["num_samples"] == len(content)
+
+
+def test_check_jsonl_invalid_weight_float(tmp_path: Path):
+    file = tmp_path / "invalid_weight_float.jsonl"
+    content = [
+        {
+            "messages": [
+                {"role": "user", "content": "Hello", "weight": 1.0},
+                {"role": "assistant", "content": "Hi there!", "weight": 0},
+            ]
+        }
+    ]
+    with file.open("w") as f:
+        f.write("\n".join(json.dumps(item) for item in content))
+
+    report = check_file(file)
+    assert not report["is_check_passed"]
+    assert "Weight must be an integer" in report["message"]
+
+
+def test_check_jsonl_invalid_weight(tmp_path: Path):
+    file = tmp_path / "invalid_weight.jsonl"
+    content = [
+        {
+            "messages": [
+                {"role": "user", "content": "Hello", "weight": 2},
+                {"role": "assistant", "content": "Hi there!", "weight": 0},
+            ]
+        }
+    ]
+    with file.open("w") as f:
+        f.write("\n".join(json.dumps(item) for item in content))
+
+    report = check_file(file)
+    assert not report["is_check_passed"]
+    assert "Weight must be either 0 or 1" in report["message"]