diff --git a/dochooks/insert_whitespace_between_cn_and_en_char/check.py b/dochooks/insert_whitespace_between_cn_and_en_char/check.py
index b2bf5c7..149bfc7 100644
--- a/dochooks/insert_whitespace_between_cn_and_en_char/check.py
+++ b/dochooks/insert_whitespace_between_cn_and_en_char/check.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import argparse
+from collections.abc import Iterable
 from typing import Sequence
 
 from dochooks import __version__
@@ -16,18 +17,27 @@ def check(string: str) -> bool:
     return True
 
 
-def _check_file(file_path: str) -> ReturnCode:
-    return_code = PASS
+def check_lines(lines: Iterable[str]) -> tuple[bool, list[tuple[int, str]]]:
+    diagnostics: list[tuple[int, str]] = []
+    need_format = False
     pragma_manager = PragmaManager()
+    for lineno, line in enumerate(lines, 1):
+        with pragma_manager.scan(line) as skip_line:
+            if skip_line:
+                continue
+            if not check(line):
+                need_format = True
+                diagnostics.append((lineno, line))
+    return need_format, diagnostics
+
+
+def _check_file(file_path: str) -> ReturnCode:
     with open(file_path, encoding="utf8", newline="\n") as f:
-        for lineno, line in enumerate(f, 1):
-            with pragma_manager.scan(line) as skip_line:
-                if skip_line:
-                    continue
-                if not check(line):
-                    print(f"No spaces between EN and CN chars detected at: {file_path}:{lineno}:\t{line}")
-                    return_code = FAIL
-    return return_code
+        need_format, diagnostics = check_lines(f)
+    if need_format:
+        for lineno, line in diagnostics:
+            print(f"No spaces between EN and CN chars detected at: {file_path}:{lineno}:\t{line}")
+    return FAIL if need_format else PASS
 
 
 def main(argv: Sequence[str] | None = None) -> ReturnCode:
diff --git a/dochooks/insert_whitespace_between_cn_and_en_char/format.py b/dochooks/insert_whitespace_between_cn_and_en_char/format.py
index 007888d..12f1c27 100644
--- a/dochooks/insert_whitespace_between_cn_and_en_char/format.py
+++ b/dochooks/insert_whitespace_between_cn_and_en_char/format.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import argparse
+from collections.abc import Iterable
 from typing import Sequence
 
 from dochooks import __version__
@@ -17,25 +18,34 @@ def format(text: str) -> str:
     return text
 
 
-def _format_file(file_path: str) -> ReturnCode:
-    return_code = PASS
+def format_lines(lines: Iterable[str]) -> tuple[bool, str, list[tuple[int, str]]]:
+    formatted_text: str = ""
+    diagnostics: list[tuple[int, str]] = []
+    need_format = False
     pragma_manager = PragmaManager()
-    formatted_text = ""
-    with open(file_path, encoding="utf8", newline="\n") as f:
-        for lineno, line in enumerate(f, 1):
-            with pragma_manager.scan(line) as skip_line:
-                if skip_line:
-                    formatted_text += line
-                    continue
-                if not check(line):
-                    line = format(line)
-                    return_code = FAIL
-                    print(f"Add spaces between EN and CN chars in: {file_path}:{lineno}:\t{line}")
+    for lineno, line in enumerate(lines, 1):
+        with pragma_manager.scan(line) as skip_line:
+            if skip_line:
                 formatted_text += line
-    if return_code != PASS:
+                continue
+            if not check(line):
+                line = format(line)
+                need_format = True
+                diagnostics.append((lineno, line))
+            formatted_text += line
+    return need_format, formatted_text, diagnostics
+
+
+def _format_file(file_path: str) -> ReturnCode:
+    with open(file_path, encoding="utf8", newline="\n") as f:
+        need_format, formatted_text, diagnostics = format_lines(f)
+
+    if formatted_text:
         with open(file_path, "w", encoding="utf8", newline="\n") as f:
             f.write(formatted_text)
-    return return_code
+        for lineno, line in diagnostics:
+            print(f"Add spaces between EN and CN chars in: {file_path}:{lineno}:\t{line}")
+    return FAIL if need_format else PASS
 
 
 def main(argv: Sequence[str] | None = None) -> ReturnCode:
diff --git a/tests/test_insert_whitespace_between_cn_and_en_char/test_pragma.py b/tests/test_insert_whitespace_between_cn_and_en_char/test_pragma.py
new file mode 100644
index 0000000..f4662fe
--- /dev/null
+++ b/tests/test_insert_whitespace_between_cn_and_en_char/test_pragma.py
@@ -0,0 +1,51 @@
+from __future__ import annotations
+
+import pytest
+
+from dochooks.insert_whitespace_between_cn_and_en_char.check import check_lines
+from dochooks.insert_whitespace_between_cn_and_en_char.format import format_lines
+
+NEED_FORMAT: bool = True
+NEEDNT_FORMAT: bool = False
+cases = [
+    (NEEDNT_FORMAT, "中文and英文 # dochooks: skip-line", "中文and英文 # dochooks: skip-line"),
+    (
+        NEED_FORMAT,
+        """
+    中文English # 需要格式化
+    中文English # dochooks: skip-line
+    中文English # 需要格式化
+    中文English # dochooks: skip-line
+    中文English # 需要格式化
+    # dochooks: skip-next-line
+    中文English
+    中文English # 需要格式化
+    # dochooks: skip-next-line
+    中文English
+    中文English # 需要格式化
+    """,
+        """
+    中文 English # 需要格式化
+    中文English # dochooks: skip-line
+    中文 English # 需要格式化
+    中文English # dochooks: skip-line
+    中文 English # 需要格式化
+    # dochooks: skip-next-line
+    中文English
+    中文 English # 需要格式化
+    # dochooks: skip-next-line
+    中文English
+    中文 English # 需要格式化
+    """,
+    ),
+]
+
+
+@pytest.mark.parametrize("need_format, unformatted, formatted", cases)
+def test_check_and_format_lines(need_format: bool, unformatted: str, formatted: str):
+    need_format_from_check, _ = check_lines(unformatted.splitlines(keepends=True))
+    need_format_from_format, formatted_text, _ = format_lines(unformatted.splitlines(keepends=True))
+    assert need_format_from_check == need_format
+    assert need_format_from_format == need_format
+
+    assert formatted_text == formatted