From 43fa349774beecced532b8151ad83fa8c2df8333 Mon Sep 17 00:00:00 2001
From: Gareth Jones <3151613+G-Rath@users.noreply.github.com>
Date: Tue, 25 Aug 2026 08:03:08 +1200
Subject: [PATCH 01/11] refactor: remove unused `read_csv` method

---
 src/output.py | 14 --------------
 1 file changed, 14 deletions(-)

diff --git a/src/output.py b/src/output.py
index aaae7ddb..b349b414 100644
--- a/src/output.py
+++ b/src/output.py
@@ -44,20 +44,6 @@ def get_file_lock(self, path: str) -> threading.Lock:
         CSVWriter.file_locks[path] = threading.Lock()
       return CSVWriter.file_locks[path]
 
-  def read_csv(self, path: str) -> list[dict[Any, Any]]:
-    """Read a CSV file as a list of dictionaries.
-
-    Args:
-        path (str): path to CSV file
-
-    Returns:
-        list[dict[Any, Any]]: list of dictionaries
-    """
-    with self.get_file_lock(path), open(path, encoding='utf-8-sig') as csvfile:
-      reader = csv.DictReader(csvfile)
-      rows = list(reader)
-    return rows
-
   def add_row(self, row: dict[Any, Any]) -> None:
     """Add a row to the CSV row buffer.
 

From aa031dcd6b905627070774c6cfbd0893b925447b Mon Sep 17 00:00:00 2001
From: Gareth Jones <3151613+G-Rath@users.noreply.github.com>
Date: Tue, 25 Aug 2026 08:03:21 +1200
Subject: [PATCH 02/11] refactor: make `get_file_lock` private

---
 src/output.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/output.py b/src/output.py
index b349b414..fee628d9 100644
--- a/src/output.py
+++ b/src/output.py
@@ -30,7 +30,7 @@ def __init__(self) -> None:
     """Init variables."""
     self.rows: list[dict[Any, Any]] = []
 
-  def get_file_lock(self, path: str) -> threading.Lock:
+  def _get_file_lock(self, path: str) -> threading.Lock:
     """Get a lock for a file.
 
     Args:
@@ -76,7 +76,7 @@ def write_csv_file(self, path: str, overwrite: bool = False) -> bool:
 
     keys = self.rows[0].keys()
 
-    with self.get_file_lock(path):
+    with self._get_file_lock(path):
       file_exists = False if overwrite else os.path.exists(path)
       file_mode = 'w' if overwrite else 'a'
       with open(path, file_mode, encoding='utf-8-sig') as csvfile:

From b3f638efe3bc3d1eb56910a315792a7fa4cc4f6d Mon Sep 17 00:00:00 2001
From: Gareth Jones <3151613+G-Rath@users.noreply.github.com>
Date: Tue, 25 Aug 2026 08:32:33 +1200
Subject: [PATCH 03/11] refactor: remove `add_row` in favor of `add_rows`

---
 src/crawler.py | 16 +++++++++-------
 src/output.py  | 10 +---------
 2 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/src/crawler.py b/src/crawler.py
index fff7389e..ff80dd6a 100644
--- a/src/crawler.py
+++ b/src/crawler.py
@@ -368,13 +368,15 @@ def are_url_headers_acceptable(self, base_url: str, parent_url: str, url_data: s
       )
       # Write bad response codes with CSVWriter
       csv_writer = src.output.CSVWriter()
-      csv_writer.add_row(
-        {
-          'base_url': base_url,
-          'parent_url': parent_url,
-          'url': url_data['final_url'],
-          'status_code': url_data['status_code'],
-        }
+      csv_writer.add_rows(
+        [
+          {
+            'base_url': base_url,
+            'parent_url': parent_url,
+            'url': url_data['final_url'],
+            'status_code': url_data['status_code'],
+          }
+        ]
       )
       if self.config.record_unexpected_response_codes:
         csv_writer.write_csv_file(f'./results/{self.config.audit_name}/unexpected_response_codes.csv')
diff --git a/src/output.py b/src/output.py
index fee628d9..bf5b40ca 100644
--- a/src/output.py
+++ b/src/output.py
@@ -44,14 +44,6 @@ def _get_file_lock(self, path: str) -> threading.Lock:
         CSVWriter.file_locks[path] = threading.Lock()
       return CSVWriter.file_locks[path]
 
-  def add_row(self, row: dict[Any, Any]) -> None:
-    """Add a row to the CSV row buffer.
-
-    Args:
-        row (dict[Any, Any]): A dictionary of row contents
-    """
-    self.rows.append(row)
-
   def add_rows(self, rows: list[dict[Any, Any]]) -> None:
     """Add a list of rows to the CSV row buffer.
 
@@ -209,7 +201,7 @@ def print_progress_bar(
     'remaining': f'{time_est}',
   }
 
-  csv_writer.add_row(output_row)
+  csv_writer.add_rows([output_row])
 
   csv_writer.write_csv_file(f'./results/{config.audit_name}/progress.csv')
 

From 9fe52898dbf43780c74f42eac782b93e9991d425 Mon Sep 17 00:00:00 2001
From: Gareth Jones <3151613+G-Rath@users.noreply.github.com>
Date: Tue, 25 Aug 2026 08:34:22 +1200
Subject: [PATCH 04/11] test: add coverage

---
 tests/test_output.py | 96 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 tests/test_output.py

diff --git a/tests/test_output.py b/tests/test_output.py
new file mode 100644
index 00000000..8adbd4c5
--- /dev/null
+++ b/tests/test_output.py
@@ -0,0 +1,96 @@
+"""Tests the behaviour of the output classes and functions."""
+
+import os
+import textwrap
+
+import pytest
+
+from src.output import CSVWriter
+
+
+@pytest.mark.usefixtures('fs')
+class TestCSVWriter:
+  """Tests writing csv files using the CSVWriter class."""
+
+  def test_csv_is_not_written_when_no_rows(self) -> None:
+    """Skips writing a file when no rows have been added."""
+    writer = CSVWriter()
+
+    assert not writer.write_csv_file('file.csv')
+
+    assert os.path.exists('file.csv') is not True
+
+  def test_csv_is_written(self) -> None:
+    """Writes each row to a csv file, with a header."""
+    writer = CSVWriter()
+
+    writer.add_rows(
+      [
+        {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
+        {'name': 'Alice', 'age': 31, 'location': 'Wellington'},
+        {'name': 'Greg', 'age': 23, 'location': 'Auckland'},
+      ]
+    )
+
+    assert writer.write_csv_file('file.csv')
+    assert os.path.exists('file.csv') is True
+
+    expected = """
+      name,age,location
+      Bob,20,Wellington
+      Alice,31,Wellington
+      Greg,23,Auckland
+    """
+
+    with open('file.csv', encoding='utf-8-sig') as f:
+      assert f.read() == textwrap.dedent(expected).lstrip()
+
+  def test_csv_is_written_with_bom(self) -> None:
+    """Writes a bom before the header row."""
+    writer = CSVWriter()
+
+    writer.add_rows(
+      [
+        {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
+        {'name': 'Alice', 'age': 31, 'location': 'Wellington'},
+        {'name': 'Greg', 'age': 23, 'location': 'Auckland'},
+      ]
+    )
+
+    assert writer.write_csv_file('file.csv')
+    assert os.path.exists('file.csv') is True
+
+    expected = """
+      \ufeffname,age,location
+      Bob,20,Wellington
+      Alice,31,Wellington
+      Greg,23,Auckland
+    """
+
+    with open('file.csv', encoding='utf-8') as f:
+      assert f.read() == textwrap.dedent(expected).lstrip()
+
+  def test_column_ordering_is_consistent(self) -> None:
+    """Orders columns based on the first row."""
+    writer = CSVWriter()
+
+    writer.add_rows(
+      [
+        {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
+        {'age': 31, 'name': 'Alice', 'location': 'Wellington'},
+        {'location': 'Auckland', 'age': 23, 'name': 'Greg'},
+      ]
+    )
+
+    assert writer.write_csv_file('file.csv')
+    assert os.path.exists('file.csv') is True
+
+    expected = """
+      name,age,location
+      Bob,20,Wellington
+      Alice,31,Wellington
+      Greg,23,Auckland
+    """
+
+    with open('file.csv', encoding='utf-8-sig') as f:
+      assert f.read() == textwrap.dedent(expected).lstrip()

From 37ca3cc2cd8c13e8fbd9ffc1284eaa98ad9e6c11 Mon Sep 17 00:00:00 2001
From: Gareth Jones <3151613+G-Rath@users.noreply.github.com>
Date: Tue, 25 Aug 2026 08:45:37 +1200
Subject: [PATCH 05/11] refactor: don't bother returning

---
 src/output.py        |  9 ++-------
 tests/test_output.py | 10 ++++++----
 2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/src/output.py b/src/output.py
index bf5b40ca..aaa3bf78 100644
--- a/src/output.py
+++ b/src/output.py
@@ -53,18 +53,15 @@ def add_rows(self, rows: list[dict[Any, Any]]) -> None:
     for row in rows:
       self.rows.append(row)
 
-  def write_csv_file(self, path: str, overwrite: bool = False) -> bool:
+  def write_csv_file(self, path: str, overwrite: bool = False) -> None:
     """Write data to a CSV file.
 
     Args:
         path (str): path to write data
         overwrite (bool): overwrite existing file
-
-    Returns:
-        bool: True if write successful, else False
     """
     if not self.rows:
-      return False
+      return
 
     keys = self.rows[0].keys()
 
@@ -79,8 +76,6 @@ def write_csv_file(self, path: str, overwrite: bool = False) -> bool:
 
     self.rows = []
 
-    return True
-
 
 def output_init_message(config: Config) -> None:
   """Print the initial message to stdout and the log."""
diff --git a/tests/test_output.py b/tests/test_output.py
index 8adbd4c5..42834a43 100644
--- a/tests/test_output.py
+++ b/tests/test_output.py
@@ -16,7 +16,7 @@ def test_csv_is_not_written_when_no_rows(self) -> None:
     """Skips writing a file when no rows have been added."""
     writer = CSVWriter()
 
-    assert not writer.write_csv_file('file.csv')
+    writer.write_csv_file('file.csv')
 
     assert os.path.exists('file.csv') is not True
 
@@ -32,7 +32,7 @@ def test_csv_is_written(self) -> None:
       ]
     )
 
-    assert writer.write_csv_file('file.csv')
+    writer.write_csv_file('file.csv')
     assert os.path.exists('file.csv') is True
 
     expected = """
@@ -57,7 +57,8 @@ def test_csv_is_written_with_bom(self) -> None:
       ]
     )
 
-    assert writer.write_csv_file('file.csv')
+    writer.write_csv_file('file.csv')
+
     assert os.path.exists('file.csv') is True
 
     expected = """
@@ -82,7 +83,8 @@ def test_column_ordering_is_consistent(self) -> None:
       ]
     )
 
-    assert writer.write_csv_file('file.csv')
+    writer.write_csv_file('file.csv')
+
     assert os.path.exists('file.csv') is True
 
     expected = """

From 0146529daf2a8849a162e659153cbc4842f5b285 Mon Sep 17 00:00:00 2001
From: Gareth Jones <3151613+G-Rath@users.noreply.github.com>
Date: Tue, 25 Aug 2026 08:47:58 +1200
Subject: [PATCH 06/11] refactor: remove overwrite param

---
 src/output.py        | 10 ++++------
 tests/test_output.py | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/src/output.py b/src/output.py
index aaa3bf78..23fa8863 100644
--- a/src/output.py
+++ b/src/output.py
@@ -53,12 +53,11 @@ def add_rows(self, rows: list[dict[Any, Any]]) -> None:
     for row in rows:
       self.rows.append(row)
 
-  def write_csv_file(self, path: str, overwrite: bool = False) -> None:
+  def write_csv_file(self, path: str) -> None:
     """Write data to a CSV file.
 
     Args:
         path (str): path to write data
-        overwrite (bool): overwrite existing file
     """
     if not self.rows:
       return
@@ -66,11 +65,10 @@ def write_csv_file(self, path: str, overwrite: bool = False) -> None:
     keys = self.rows[0].keys()
 
     with self._get_file_lock(path):
-      file_exists = False if overwrite else os.path.exists(path)
-      file_mode = 'w' if overwrite else 'a'
-      with open(path, file_mode, encoding='utf-8-sig') as csvfile:
+      file_already_exists = os.path.exists(path)
+      with open(path, 'a', encoding='utf-8-sig') as csvfile:
         writer = csv.DictWriter(csvfile, fieldnames=keys)
-        if not file_exists:
+        if not file_already_exists:
           writer.writeheader()
         writer.writerows(self.rows)
 
diff --git a/tests/test_output.py b/tests/test_output.py
index 42834a43..6081a619 100644
--- a/tests/test_output.py
+++ b/tests/test_output.py
@@ -71,6 +71,39 @@ def test_csv_is_written_with_bom(self) -> None:
     with open('file.csv', encoding='utf-8') as f:
       assert f.read() == textwrap.dedent(expected).lstrip()
 
+  def test_multiple_writes_to_same_file(self) -> None:
+    """Writes new rows to a csv file, without duplicating the header."""
+    writer = CSVWriter()
+
+    writer.add_rows(
+      [
+        {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
+      ]
+    )
+
+    writer.write_csv_file('file.csv')
+
+    assert os.path.exists('file.csv') is True
+
+    writer.add_rows(
+      [
+        {'name': 'Alice', 'age': 31, 'location': 'Wellington'},
+        {'name': 'Greg', 'age': 23, 'location': 'Auckland'},
+      ]
+    )
+
+    writer.write_csv_file('file.csv')
+
+    expected = """
+      name,age,location
+      Bob,20,Wellington
+      Alice,31,Wellington
+      Greg,23,Auckland
+    """
+
+    with open('file.csv', encoding='utf-8-sig') as f:
+      assert f.read() == textwrap.dedent(expected).lstrip()
+
   def test_column_ordering_is_consistent(self) -> None:
     """Orders columns based on the first row."""
     writer = CSVWriter()

From 187b930083919ed9594b7c1c4e8e8716f334b2a4 Mon Sep 17 00:00:00 2001
From: Gareth Jones <3151613+G-Rath@users.noreply.github.com>
Date: Tue, 25 Aug 2026 08:58:00 +1200
Subject: [PATCH 07/11] refactor: take rows as a variadic param

---
 src/audit_manager.py | 20 +++++++++-----------
 src/crawler.py       | 42 ++++++++++++++++++------------------------
 src/output.py        |  4 ++--
 tests/test_output.py | 34 ++++++++++++----------------------
 4 files changed, 41 insertions(+), 59 deletions(-)

diff --git a/src/audit_manager.py b/src/audit_manager.py
index b90dc993..fd5d8ba1 100644
--- a/src/audit_manager.py
+++ b/src/audit_manager.py
@@ -138,15 +138,13 @@ def test_for_anti_bot(self) -> str:
       # Write to anti-bot.csv
       csv_writer = CSVWriter()
       csv_writer.add_rows(
-        [
-          {
-            'organisation': org['organisation'],
-            'domain': netloc,
-            'url': url,
-            'anti_bot_check': status,
-            'viewport_size': self.browser.viewport_size,
-          }
-        ]
+        {
+          'organisation': org['organisation'],
+          'domain': netloc,
+          'url': url,
+          'anti_bot_check': status,
+          'viewport_size': self.browser.viewport_size,
+        }
       )
       csv_writer.write_csv_file(f'./results/{self.config.audit_name}/anti_bot.csv')
       self.discarded_urls[url] = status
@@ -287,7 +285,7 @@ def run_audits(self) -> bool:  # noqa: PLR0915
         test_instance = audit['audit_class'](config=self.config, browser=self.browser, **audit['kwargs'])
 
         try:
-          audit_result = test_instance.run()
+          audit_result: list[dict[str, Any]] | bool = test_instance.run()
         except selenium.common.exceptions.WebDriverException:
           logger.exception(
             'Due to WebDriverException, test %s skipped on viewport %s for website %s',
@@ -359,7 +357,7 @@ def run_audits(self) -> bool:  # noqa: PLR0915
 
         # Write results
         csv_writer = CSVWriter()
-        csv_writer.add_rows(audit_result)
+        csv_writer.add_rows(*audit_result)
         csv_writer.write_csv_file(f'./results/{self.config.audit_name}/{audit_name}.csv')
 
         # At least one audit successfully produced results
diff --git a/src/crawler.py b/src/crawler.py
index ff80dd6a..33160672 100644
--- a/src/crawler.py
+++ b/src/crawler.py
@@ -369,14 +369,12 @@ def are_url_headers_acceptable(self, base_url: str, parent_url: str, url_data: s
       # Write bad response codes with CSVWriter
       csv_writer = src.output.CSVWriter()
       csv_writer.add_rows(
-        [
-          {
-            'base_url': base_url,
-            'parent_url': parent_url,
-            'url': url_data['final_url'],
-            'status_code': url_data['status_code'],
-          }
-        ]
+        {
+          'base_url': base_url,
+          'parent_url': parent_url,
+          'url': url_data['final_url'],
+          'status_code': url_data['status_code'],
+        }
       )
       if self.config.record_unexpected_response_codes:
         csv_writer.write_csv_file(f'./results/{self.config.audit_name}/unexpected_response_codes.csv')
@@ -575,14 +573,12 @@ def crawl(self, site_data: SiteData, base_url: str) -> None:  # noqa: PLR0912, P
       # Write to audit_log.csv
       csv_writer = CSVWriter()
       csv_writer.add_rows(
-        [
-          {
-            'organisation': site_data['organisation'],
-            'base_url': site_data['url'],
-            'url': url,
-            'sector': site_data['sector'],
-          }
-        ]
+        {
+          'organisation': site_data['organisation'],
+          'base_url': site_data['url'],
+          'url': url,
+          'sector': site_data['sector'],
+        }
       )
       csv_writer.write_csv_file(f'./results/{self.config.audit_name}/audit_log.csv')
 
@@ -652,14 +648,12 @@ def record_pages_scanned(self, site_data: SiteData, pages_scanned: int) -> None:
     with self.config.lock:
       csv_writer = src.output.CSVWriter()
       csv_writer.add_rows(
-        [
-          {
-            'organisation': site_data['organisation'],
-            'base_url': site_data['url'],
-            'number_of_pages': pages_scanned,
-            'sector': site_data['sector'],
-          }
-        ]
+        {
+          'organisation': site_data['organisation'],
+          'base_url': site_data['url'],
+          'number_of_pages': pages_scanned,
+          'sector': site_data['sector'],
+        }
       )
       csv_writer.write_csv_file(f'./results/{self.config.audit_name}/pages_scanned.csv')
 
diff --git a/src/output.py b/src/output.py
index 23fa8863..1b1ab728 100644
--- a/src/output.py
+++ b/src/output.py
@@ -44,7 +44,7 @@ def _get_file_lock(self, path: str) -> threading.Lock:
         CSVWriter.file_locks[path] = threading.Lock()
       return CSVWriter.file_locks[path]
 
-  def add_rows(self, rows: list[dict[Any, Any]]) -> None:
+  def add_rows(self, *rows: dict[Any, Any]) -> None:
     """Add a list of rows to the CSV row buffer.
 
     Args:
@@ -194,7 +194,7 @@ def print_progress_bar(
     'remaining': f'{time_est}',
   }
 
-  csv_writer.add_rows([output_row])
+  csv_writer.add_rows(output_row)
 
   csv_writer.write_csv_file(f'./results/{config.audit_name}/progress.csv')
 
diff --git a/tests/test_output.py b/tests/test_output.py
index 6081a619..de2f9e56 100644
--- a/tests/test_output.py
+++ b/tests/test_output.py
@@ -25,11 +25,9 @@ def test_csv_is_written(self) -> None:
     writer = CSVWriter()
 
     writer.add_rows(
-      [
-        {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
-        {'name': 'Alice', 'age': 31, 'location': 'Wellington'},
-        {'name': 'Greg', 'age': 23, 'location': 'Auckland'},
-      ]
+      {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
+      {'name': 'Alice', 'age': 31, 'location': 'Wellington'},
+      {'name': 'Greg', 'age': 23, 'location': 'Auckland'},
     )
 
     writer.write_csv_file('file.csv')
@@ -50,11 +48,9 @@ def test_csv_is_written_with_bom(self) -> None:
     writer = CSVWriter()
 
     writer.add_rows(
-      [
-        {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
-        {'name': 'Alice', 'age': 31, 'location': 'Wellington'},
-        {'name': 'Greg', 'age': 23, 'location': 'Auckland'},
-      ]
+      {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
+      {'name': 'Alice', 'age': 31, 'location': 'Wellington'},
+      {'name': 'Greg', 'age': 23, 'location': 'Auckland'},
     )
 
     writer.write_csv_file('file.csv')
@@ -76,9 +72,7 @@ def test_multiple_writes_to_same_file(self) -> None:
     writer = CSVWriter()
 
     writer.add_rows(
-      [
-        {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
-      ]
+      {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
     )
 
     writer.write_csv_file('file.csv')
@@ -86,10 +80,8 @@ def test_multiple_writes_to_same_file(self) -> None:
     assert os.path.exists('file.csv') is True
 
     writer.add_rows(
-      [
-        {'name': 'Alice', 'age': 31, 'location': 'Wellington'},
-        {'name': 'Greg', 'age': 23, 'location': 'Auckland'},
-      ]
+      {'name': 'Alice', 'age': 31, 'location': 'Wellington'},
+      {'name': 'Greg', 'age': 23, 'location': 'Auckland'},
     )
 
     writer.write_csv_file('file.csv')
@@ -109,11 +101,9 @@ def test_column_ordering_is_consistent(self) -> None:
     writer = CSVWriter()
 
     writer.add_rows(
-      [
-        {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
-        {'age': 31, 'name': 'Alice', 'location': 'Wellington'},
-        {'location': 'Auckland', 'age': 23, 'name': 'Greg'},
-      ]
+      {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
+      {'age': 31, 'name': 'Alice', 'location': 'Wellington'},
+      {'location': 'Auckland', 'age': 23, 'name': 'Greg'},
     )
 
     writer.write_csv_file('file.csv')

From 462a1118c39842f5fe597f1907d558e3c1bd3540 Mon Sep 17 00:00:00 2001
From: Gareth Jones <3151613+G-Rath@users.noreply.github.com>
Date: Tue, 25 Aug 2026 10:06:16 +1200
Subject: [PATCH 08/11] refactor: merge `add_rows` and `write_csv_file`

---
 src/audit_manager.py | 10 ++++-----
 src/crawler.py       | 33 ++++++++++++++--------------
 src/output.py        | 52 +++++++++++++++-----------------------------
 tests/test_output.py | 28 ++++++++++--------------
 4 files changed, 51 insertions(+), 72 deletions(-)

diff --git a/src/audit_manager.py b/src/audit_manager.py
index fd5d8ba1..2210416b 100644
--- a/src/audit_manager.py
+++ b/src/audit_manager.py
@@ -137,16 +137,17 @@ def test_for_anti_bot(self) -> str:
 
       # Write to anti-bot.csv
       csv_writer = CSVWriter()
-      csv_writer.add_rows(
+      csv_writer.append_rows(
+        f'./results/{self.config.audit_name}/anti_bot.csv',
         {
           'organisation': org['organisation'],
           'domain': netloc,
           'url': url,
           'anti_bot_check': status,
           'viewport_size': self.browser.viewport_size,
-        }
+        },
       )
-      csv_writer.write_csv_file(f'./results/{self.config.audit_name}/anti_bot.csv')
+
       self.discarded_urls[url] = status
 
     return status
@@ -357,8 +358,7 @@ def run_audits(self) -> bool:  # noqa: PLR0915
 
         # Write results
         csv_writer = CSVWriter()
-        csv_writer.add_rows(*audit_result)
-        csv_writer.write_csv_file(f'./results/{self.config.audit_name}/{audit_name}.csv')
+        csv_writer.append_rows(f'./results/{self.config.audit_name}/{audit_name}.csv', *audit_result)
 
         # At least one audit successfully produced results
         any_audit_succeeded = True
diff --git a/src/crawler.py b/src/crawler.py
index 33160672..6a00c286 100644
--- a/src/crawler.py
+++ b/src/crawler.py
@@ -366,18 +366,17 @@ def are_url_headers_acceptable(self, base_url: str, parent_url: str, url_data: s
         url_data['final_url'],
         url_data['status_code'],
       )
-      # Write bad response codes with CSVWriter
-      csv_writer = src.output.CSVWriter()
-      csv_writer.add_rows(
-        {
-          'base_url': base_url,
-          'parent_url': parent_url,
-          'url': url_data['final_url'],
-          'status_code': url_data['status_code'],
-        }
-      )
       if self.config.record_unexpected_response_codes:
-        csv_writer.write_csv_file(f'./results/{self.config.audit_name}/unexpected_response_codes.csv')
+        csv_writer = src.output.CSVWriter()
+        csv_writer.append_rows(
+          f'./results/{self.config.audit_name}/unexpected_response_codes.csv',
+          {
+            'base_url': base_url,
+            'parent_url': parent_url,
+            'url': url_data['final_url'],
+            'status_code': url_data['status_code'],
+          },
+        )
 
       return False
     return src.filters.url_filter_by_header_content_type(url_data['final_url'], url_data['headers'])
@@ -572,15 +571,15 @@ def crawl(self, site_data: SiteData, base_url: str) -> None:  # noqa: PLR0912, P
 
       # Write to audit_log.csv
       csv_writer = CSVWriter()
-      csv_writer.add_rows(
+      csv_writer.append_rows(
+        f'./results/{self.config.audit_name}/audit_log.csv',
         {
           'organisation': site_data['organisation'],
           'base_url': site_data['url'],
           'url': url,
           'sector': site_data['sector'],
-        }
+        },
       )
-      csv_writer.write_csv_file(f'./results/{self.config.audit_name}/audit_log.csv')
 
       self.register_audit_plugins(audit_manager, url, site_data)
       test_success = audit_manager.run_audits()
@@ -647,15 +646,15 @@ def record_pages_scanned(self, site_data: SiteData, pages_scanned: int) -> None:
     """Record the number of pages that were scanned for the site."""
     with self.config.lock:
       csv_writer = src.output.CSVWriter()
-      csv_writer.add_rows(
+      csv_writer.append_rows(
+        f'./results/{self.config.audit_name}/pages_scanned.csv',
         {
           'organisation': site_data['organisation'],
           'base_url': site_data['url'],
           'number_of_pages': pages_scanned,
           'sector': site_data['sector'],
-        }
+        },
       )
-      csv_writer.write_csv_file(f'./results/{self.config.audit_name}/pages_scanned.csv')
 
 
 class RandomQueue[T]:
diff --git a/src/output.py b/src/output.py
index 1b1ab728..664f4d9f 100644
--- a/src/output.py
+++ b/src/output.py
@@ -26,10 +26,6 @@ class CSVWriter:
   # A lock to prevent multiple threads writing to file_locks dict
   lock_for_file_locks = threading.Lock()
 
-  def __init__(self) -> None:
-    """Init variables."""
-    self.rows: list[dict[Any, Any]] = []
-
   def _get_file_lock(self, path: str) -> threading.Lock:
     """Get a lock for a file.
 
@@ -44,25 +40,17 @@ def _get_file_lock(self, path: str) -> threading.Lock:
         CSVWriter.file_locks[path] = threading.Lock()
       return CSVWriter.file_locks[path]
 
-  def add_rows(self, *rows: dict[Any, Any]) -> None:
-    """Add a list of rows to the CSV row buffer.
+  def append_rows(self, path: str, *rows: dict[Any, Any]) -> None:
+    """Add a list of rows to a CSV file.
 
     Args:
+        path (str): path to file
         rows (list[dict[Any, Any]]): list of rows of data
     """
-    for row in rows:
-      self.rows.append(row)
-
-  def write_csv_file(self, path: str) -> None:
-    """Write data to a CSV file.
-
-    Args:
-        path (str): path to write data
-    """
-    if not self.rows:
+    if not rows:
       return
 
-    keys = self.rows[0].keys()
+    keys = rows[0].keys()
 
     with self._get_file_lock(path):
       file_already_exists = os.path.exists(path)
@@ -70,9 +58,7 @@ def write_csv_file(self, path: str) -> None:
         writer = csv.DictWriter(csvfile, fieldnames=keys)
         if not file_already_exists:
           writer.writeheader()
-        writer.writerows(self.rows)
-
-    self.rows = []
+        writer.writerows(rows)
 
 
 def output_init_message(config: Config) -> None:
@@ -183,20 +169,18 @@ def print_progress_bar(
 
   # Write progress data to CSV file
   csv_writer = CSVWriter()
-
-  output_row = {
-    'time': time.time(),
-    'iteration': iteration,
-    'total': total,
-    'speed': f'{speed:.2f}',
-    'percent': percent,
-    'elapsed': f'{elapsed}',
-    'remaining': f'{time_est}',
-  }
-
-  csv_writer.add_rows(output_row)
-
-  csv_writer.write_csv_file(f'./results/{config.audit_name}/progress.csv')
+  csv_writer.append_rows(
+    f'./results/{config.audit_name}/progress.csv',
+    {
+      'time': time.time(),
+      'iteration': iteration,
+      'total': total,
+      'speed': f'{speed:.2f}',
+      'percent': percent,
+      'elapsed': f'{elapsed}',
+      'remaining': f'{time_est}',
+    },
+  )
 
   # Print New Line on Complete
   if iteration == total:
diff --git a/tests/test_output.py b/tests/test_output.py
index de2f9e56..34fb850b 100644
--- a/tests/test_output.py
+++ b/tests/test_output.py
@@ -16,7 +16,7 @@ def test_csv_is_not_written_when_no_rows(self) -> None:
     """Skips writing a file when no rows have been added."""
     writer = CSVWriter()
 
-    writer.write_csv_file('file.csv')
+    writer.append_rows('file.csv')
 
     assert os.path.exists('file.csv') is not True
 
@@ -24,13 +24,13 @@ def test_csv_is_written(self) -> None:
     """Writes each row to a csv file, with a header."""
     writer = CSVWriter()
 
-    writer.add_rows(
+    writer.append_rows(
+      'file.csv',
       {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
       {'name': 'Alice', 'age': 31, 'location': 'Wellington'},
       {'name': 'Greg', 'age': 23, 'location': 'Auckland'},
     )
 
-    writer.write_csv_file('file.csv')
     assert os.path.exists('file.csv') is True
 
     expected = """
@@ -47,14 +47,13 @@ def test_csv_is_written_with_bom(self) -> None:
     """Writes a bom before the header row."""
     writer = CSVWriter()
 
-    writer.add_rows(
+    writer.append_rows(
+      'file.csv',
       {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
       {'name': 'Alice', 'age': 31, 'location': 'Wellington'},
       {'name': 'Greg', 'age': 23, 'location': 'Auckland'},
     )
 
-    writer.write_csv_file('file.csv')
-
     assert os.path.exists('file.csv') is True
 
     expected = """
@@ -67,25 +66,23 @@ def test_csv_is_written_with_bom(self) -> None:
     with open('file.csv', encoding='utf-8') as f:
       assert f.read() == textwrap.dedent(expected).lstrip()
 
-  def test_multiple_writes_to_same_file(self) -> None:
+  def test_appends_to_existing_file(self) -> None:
     """Writes new rows to a csv file, without duplicating the header."""
     writer = CSVWriter()
 
-    writer.add_rows(
+    writer.append_rows(
+      'file.csv',
       {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
     )
 
-    writer.write_csv_file('file.csv')
-
     assert os.path.exists('file.csv') is True
 
-    writer.add_rows(
+    writer.append_rows(
+      'file.csv',
       {'name': 'Alice', 'age': 31, 'location': 'Wellington'},
       {'name': 'Greg', 'age': 23, 'location': 'Auckland'},
     )
 
-    writer.write_csv_file('file.csv')
-
     expected = """
       name,age,location
       Bob,20,Wellington
@@ -100,14 +97,13 @@ def test_column_ordering_is_consistent(self) -> None:
     """Orders columns based on the first row."""
     writer = CSVWriter()
 
-    writer.add_rows(
+    writer.append_rows(
+      'file.csv',
       {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
       {'age': 31, 'name': 'Alice', 'location': 'Wellington'},
       {'location': 'Auckland', 'age': 23, 'name': 'Greg'},
     )
 
-    writer.write_csv_file('file.csv')
-
     assert os.path.exists('file.csv') is True
 
     expected = """

From 19629b3e0b9fa2fa6e08ece4be1e8ed990318f97 Mon Sep 17 00:00:00 2001
From: Gareth Jones <3151613+G-Rath@users.noreply.github.com>
Date: Tue, 25 Aug 2026 10:12:09 +1200
Subject: [PATCH 09/11] chore: remove unneeded disable

---
 src/output.py | 2 --
 1 file changed, 2 deletions(-)

diff --git a/src/output.py b/src/output.py
index 664f4d9f..c67d9c89 100644
--- a/src/output.py
+++ b/src/output.py
@@ -11,8 +11,6 @@
 
 from config import Config
 
-# pylint: disable=too-many-locals
-
 logger = logging.getLogger('cwac')
 
 

From 07f9adf35bcca1ce78f9f851944a2f836b7c4754 Mon Sep 17 00:00:00 2001
From: Gareth Jones <3151613+G-Rath@users.noreply.github.com>
Date: Tue, 25 Aug 2026 10:16:58 +1200
Subject: [PATCH 10/11] chore: update doc comment

---
 src/output.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/output.py b/src/output.py
index c67d9c89..cf2ffb07 100644
--- a/src/output.py
+++ b/src/output.py
@@ -39,11 +39,11 @@ def _get_file_lock(self, path: str) -> threading.Lock:
       return CSVWriter.file_locks[path]
 
   def append_rows(self, path: str, *rows: dict[Any, Any]) -> None:
-    """Add a list of rows to a CSV file.
+    """Append one or more rows to a CSV file.
 
     Args:
         path (str): path to file
-        rows (list[dict[Any, Any]]): list of rows of data
+        *rows (dict[str, Any]): one or more rows of data
     """
     if not rows:
       return

From 4c8453aa5b92b5d8a0dffc4ef68d1d7ba434d2af Mon Sep 17 00:00:00 2001
From: Gareth Jones <3151613+G-Rath@users.noreply.github.com>
Date: Tue, 25 Aug 2026 10:23:05 +1200
Subject: [PATCH 11/11] test: add more coverage

---
 tests/test_output.py | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/tests/test_output.py b/tests/test_output.py
index 34fb850b..11adabb8 100644
--- a/tests/test_output.py
+++ b/tests/test_output.py
@@ -93,6 +93,44 @@ def test_appends_to_existing_file(self) -> None:
     with open('file.csv', encoding='utf-8-sig') as f:
       assert f.read() == textwrap.dedent(expected).lstrip()
 
+  def test_ignores_missing_columns(self) -> None:
+    """Ignores columns missing in subsequent rows."""
+    writer = CSVWriter()
+
+    writer.append_rows(
+      'file.csv',
+      {'name': 'Bob', 'age': 20, 'location': 'Wellington'},
+      {'name': 'Alice', 'age': 31},
+      {'age': 23, 'location': 'Auckland'},
+    )
+
+    assert os.path.exists('file.csv') is True
+
+    expected = """
+      name,age,location
+      Bob,20,Wellington
+      Alice,31,
+      ,23,Auckland
+    """
+
+    with open('file.csv', encoding='utf-8-sig') as f:
+      assert f.read() == textwrap.dedent(expected).lstrip()
+
+  def test_raises_extra_columns(self) -> None:
+    """Errors when rows have extra columns."""
+    writer = CSVWriter()
+
+    with pytest.raises(ValueError):
+      writer.append_rows(
+        'file.csv',
+        {'name': 'Bob', 'age': 20},
+        {'name': 'Alice', 'age': 31, 'location': 'Wellington'},
+        {'name': 'Greg', 'age': 23, 'location': 'Auckland'},
+      )
+
+    # the file will still end up being created due to the open mode
+    assert os.path.exists('file.csv')
+
   def test_column_ordering_is_consistent(self) -> None:
     """Orders columns based on the first row."""
     writer = CSVWriter()