From 0c42ffe551eeef3710c59b4db960b1be18a71538 Mon Sep 17 00:00:00 2001
From: Meher <mehergupta06@gmail.com>
Date: Thu, 8 Jan 2026 18:16:29 +0530
Subject: [PATCH 1/3] MINOR: [docs][C++] Clarify ARROW_TEST_DATA requirement
 for tests

---
 docs/source/developers/cpp/building.rst | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/docs/source/developers/cpp/building.rst b/docs/source/developers/cpp/building.rst
index 33530779f58..767e9f107d1 100644
--- a/docs/source/developers/cpp/building.rst
+++ b/docs/source/developers/cpp/building.rst
@@ -322,6 +322,26 @@ environment variable (which requires the ``locales`` package or equivalent):
 
    $ export LC_ALL="en_US.UTF-8"
 
+
+.. note::
+   If you are building with tests (``-DARROW_BUILD_TESTS=ON``), you must ensure
+   the test data submodules are initialized and the environment variables
+   ``ARROW_TEST_DATA`` and ``PARQUET_TEST_DATA`` are set. Without these, several
+   tests (especially IPC and Parquet tests) will fail with an ``IOError``.
+
+   To initialize submodules, run:
+
+   .. code-block:: shell
+
+      $ git submodule update --init --recursive
+
+   Then set the variables to the absolute paths of your testing data folders:
+
+   .. code-block:: shell
+
+      $ export ARROW_TEST_DATA="<absolute_path_to_arrow>/testing/data"
+      $ export PARQUET_TEST_DATA="<absolute_path_to_arrow>/cpp/submodules/parquet-testing/data"
+      
 Faster builds with Ninja
 ~~~~~~~~~~~~~~~~~~~~~~~~
 

From 9e3f21ac29d261629d2803eef58cb9c4db9d0092 Mon Sep 17 00:00:00 2001
From: Meher <mehergupta06@gmail.com>
Date: Thu, 8 Jan 2026 22:37:24 +0530
Subject: [PATCH 2/3] docs: move test data note for better visibility

---
 docs/source/developers/cpp/building.rst | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/docs/source/developers/cpp/building.rst b/docs/source/developers/cpp/building.rst
index 767e9f107d1..fa954277851 100644
--- a/docs/source/developers/cpp/building.rst
+++ b/docs/source/developers/cpp/building.rst
@@ -314,15 +314,6 @@ The unit tests are not built by default. After building, one can also invoke
 the unit tests using the ``ctest`` tool provided by CMake (note that ``test``
 depends on ``python`` being available).
 
-On some Linux distributions, running the test suite might require setting an
-explicit locale. If you see any locale-related errors, try setting the
-environment variable (which requires the ``locales`` package or equivalent):
-
-.. code-block::
-
-   $ export LC_ALL="en_US.UTF-8"
-
-
 .. note::
    If you are building with tests (``-DARROW_BUILD_TESTS=ON``), you must ensure
    the test data submodules are initialized and the environment variables
@@ -341,7 +332,15 @@ environment variable (which requires the ``locales`` package or equivalent):
 
       $ export ARROW_TEST_DATA="<absolute_path_to_arrow>/testing/data"
       $ export PARQUET_TEST_DATA="<absolute_path_to_arrow>/cpp/submodules/parquet-testing/data"
-      
+  
+On some Linux distributions, running the test suite might require setting an
+explicit locale. If you see any locale-related errors, try setting the
+environment variable (which requires the ``locales`` package or equivalent):
+
+.. code-block::
+
+   $ export LC_ALL="en_US.UTF-8"
+    
 Faster builds with Ninja
 ~~~~~~~~~~~~~~~~~~~~~~~~
 

From 7d448346a4981b8aac0aaace92cc94b9660eed20 Mon Sep 17 00:00:00 2001
From: Meher <mehergupta06@gmail.com>
Date: Fri, 9 Jan 2026 14:55:09 +0530
Subject: [PATCH 3/3] docs: remove trailing whitespace in building.rst

---
 docs/source/developers/cpp/building.rst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/docs/source/developers/cpp/building.rst b/docs/source/developers/cpp/building.rst
index fa954277851..fb681522878 100644
--- a/docs/source/developers/cpp/building.rst
+++ b/docs/source/developers/cpp/building.rst
@@ -332,7 +332,7 @@ depends on ``python`` being available).
 
       $ export ARROW_TEST_DATA="<absolute_path_to_arrow>/testing/data"
       $ export PARQUET_TEST_DATA="<absolute_path_to_arrow>/cpp/submodules/parquet-testing/data"
-  
+
 On some Linux distributions, running the test suite might require setting an
 explicit locale. If you see any locale-related errors, try setting the
 environment variable (which requires the ``locales`` package or equivalent):
@@ -340,7 +340,7 @@ environment variable (which requires the ``locales`` package or equivalent):
 .. code-block::
 
    $ export LC_ALL="en_US.UTF-8"
-    
+
 Faster builds with Ninja
 ~~~~~~~~~~~~~~~~~~~~~~~~