diff --git a/api/tests/unit_tests/libs/test_file_utils.py b/api/tests/unit_tests/libs/test_file_utils.py
new file mode 100644
index 0000000000..8d9b4e803a
--- /dev/null
+++ b/api/tests/unit_tests/libs/test_file_utils.py
@@ -0,0 +1,55 @@
+from pathlib import Path
+
+import pytest
+
+from libs.file_utils import search_file_upwards
+
+
+def test_search_file_upwards_found_in_parent(tmp_path: Path):
+    base = tmp_path / "a" / "b" / "c"
+    base.mkdir(parents=True)
+
+    target = tmp_path / "a" / "target.txt"
+    target.write_text("ok", encoding="utf-8")
+
+    found = search_file_upwards(base, "target.txt", max_search_parent_depth=5)
+    assert found == target
+
+
+def test_search_file_upwards_found_in_current(tmp_path: Path):
+    base = tmp_path / "x"
+    base.mkdir()
+    target = base / "here.txt"
+    target.write_text("x", encoding="utf-8")
+
+    found = search_file_upwards(base, "here.txt", max_search_parent_depth=1)
+    assert found == target
+
+
+def test_search_file_upwards_not_found_raises(tmp_path: Path):
+    base = tmp_path / "m" / "n"
+    base.mkdir(parents=True)
+    with pytest.raises(ValueError) as exc:
+        search_file_upwards(base, "missing.txt", max_search_parent_depth=3)
+    # error message should contain file name and base path
+    msg = str(exc.value)
+    assert "missing.txt" in msg
+    assert str(base) in msg
+
+
+def test_search_file_upwards_root_breaks_and_raises():
+    # Using filesystem root triggers the 'break' branch (parent == current)
+    with pytest.raises(ValueError):
+        search_file_upwards(Path("/"), "__definitely_not_exists__.txt", max_search_parent_depth=1)
+
+
+def test_search_file_upwards_depth_limit_raises(tmp_path: Path):
+    base = tmp_path / "a" / "b" / "c"
+    base.mkdir(parents=True)
+    target = tmp_path / "a" / "target.txt"
+    target.write_text("ok", encoding="utf-8")
+    # The file is 2 levels up from `c` (in `a`), but search depth is only 2.
+    # The search path is `c` (depth 1) -> `b` (depth 2). The file is in `a` (would need depth 3).
+    # So, this should not find the file and should raise an error.
+    with pytest.raises(ValueError):
+        search_file_upwards(base, "target.txt", max_search_parent_depth=2)
diff --git a/api/tests/unit_tests/libs/test_json_in_md_parser.py b/api/tests/unit_tests/libs/test_json_in_md_parser.py
new file mode 100644
index 0000000000..53fd0bea16
--- /dev/null
+++ b/api/tests/unit_tests/libs/test_json_in_md_parser.py
@@ -0,0 +1,88 @@
+import pytest
+
+from core.llm_generator.output_parser.errors import OutputParserError
+from libs.json_in_md_parser import (
+    parse_and_check_json_markdown,
+    parse_json_markdown,
+)
+
+
+def test_parse_json_markdown_triple_backticks_json():
+    src = """
+    ```json
+    {"a": 1, "b": "x"}
+    ```
+    """
+    assert parse_json_markdown(src) == {"a": 1, "b": "x"}
+
+
+def test_parse_json_markdown_triple_backticks_generic():
+    src = """
+    ```
+    {"k": [1, 2, 3]}
+    ```
+    """
+    assert parse_json_markdown(src) == {"k": [1, 2, 3]}
+
+
+def test_parse_json_markdown_single_backticks():
+    src = '`{"x": true}`'
+    assert parse_json_markdown(src) == {"x": True}
+
+
+def test_parse_json_markdown_braces_only():
+    src = '  {\n  \t"ok": "yes"\n}  '
+    assert parse_json_markdown(src) == {"ok": "yes"}
+
+
+def test_parse_json_markdown_not_found():
+    with pytest.raises(ValueError):
+        parse_json_markdown("no json here")
+
+
+def test_parse_and_check_json_markdown_missing_key():
+    src = """
+    ```
+    {"present": 1}
+    ```
+    """
+    with pytest.raises(OutputParserError) as exc:
+        parse_and_check_json_markdown(src, ["present", "missing"])
+    assert "expected key `missing`" in str(exc.value)
+
+
+def test_parse_and_check_json_markdown_invalid_json():
+    src = """
+    ```json
+    {invalid json}
+    ```
+    """
+    with pytest.raises(OutputParserError) as exc:
+        parse_and_check_json_markdown(src, [])
+    assert "got invalid json object" in str(exc.value)
+
+
+def test_parse_and_check_json_markdown_success():
+    src = """
+    ```json
+    {"present": 1, "other": 2}
+    ```
+    """
+    obj = parse_and_check_json_markdown(src, ["present"])
+    assert obj == {"present": 1, "other": 2}
+
+
+def test_parse_and_check_json_markdown_multiple_blocks_fails():
+    src = """
+    ```json
+    {"a": 1}
+    ```
+    Some text
+    ```json
+    {"b": 2}
+    ```
+    """
+    # The current implementation is greedy and will match from the first
+    # opening fence to the last closing fence, causing JSON decode failure.
+    with pytest.raises(OutputParserError):
+        parse_and_check_json_markdown(src, [])
diff --git a/api/tests/unit_tests/libs/test_orjson.py b/api/tests/unit_tests/libs/test_orjson.py
new file mode 100644
index 0000000000..6df1d077df
--- /dev/null
+++ b/api/tests/unit_tests/libs/test_orjson.py
@@ -0,0 +1,25 @@
+import orjson
+import pytest
+
+from libs.orjson import orjson_dumps
+
+
+def test_orjson_dumps_round_trip_basic():
+    obj = {"a": 1, "b": [1, 2, 3], "c": {"d": True}}
+    s = orjson_dumps(obj)
+    assert orjson.loads(s) == obj
+
+
+def test_orjson_dumps_with_unicode_and_indent():
+    obj = {"msg": "你好，Dify"}
+    s = orjson_dumps(obj, option=orjson.OPT_INDENT_2)
+    # contains indentation newline/spaces
+    assert "\n" in s
+    assert orjson.loads(s) == obj
+
+
+def test_orjson_dumps_non_utf8_encoding_fails():
+    obj = {"msg": "你好"}
+    # orjson.dumps() always produces UTF-8 bytes; decoding with non-UTF8 fails.
+    with pytest.raises(UnicodeDecodeError):
+        orjson_dumps(obj, encoding="ascii")