Github user steveloughran commented on a diff in the pull request:
https://github.com/apache/spark/pull/13217#discussion_r64032005
--- Diff: R/WINDOWS.md ---
@@ -11,3 +11,19 @@ include Rtools and R in `PATH`.
directory in Maven in `PATH`.
4. Set `MAVEN_OPTS` as described in [Building
Spark](http://spark.apache.org/docs/latest/building-spark.html).
5. Open a command shell (`cmd`) in the Spark directory and run `mvn
-DskipTests -Psparkr package`
+
+## Unit tests
+
+To run existing unit tests in SparkR on Windows, the following setps are
required (the steps below suppose you are in Spark root directory)
+
+1. Set `HADOOP_HOME`.
+2. Download `winutils.exe` and locate this in `$HADOOP_HOME/bin`.
+
+ It seems not requiring installing Hadoop but only this `winutils.exe`.
It seems not included in Hadoop official binary releases so it should be built
from source but it seems it is able to be downloaded from community (e.g.
[steveloughran/winutils](https://github.com/steveloughran/winutils)).
--- End diff --
I wouldn't recommend putting it under the root of the project, as that only
complicates the source tree and path cleanup; an adjacent directory works. And
I think you may find that `HADOOP.DLL` is needed in places, as there are some
JNI calls related to local file access and permissions/ACLs
I'd suggest the following text:
----
To run the SparkR unit tests on Windows, the following steps are required
âassuming you are in the Spark root directory and do not have Apache Hadoop
installed already:
1. `cd ..`
1. `mkdir hadoop`
1. Download the relevant Hadoop bin package from
[steveloughran/winutils](https://github.com/steveloughran/winutils). While
these are not official ASF artifacts, they are built from the ASF release git
hashes by a Hadoop PMC member on a dedicated Windows VM.
1. Install the files into `hadoop\bin`; make sure that `winutils.exe` and
`hadoop.dll` are present.
1. Set the environment variable `HADOOP_HOME` to the full path to the newly
created `hadoop` directory.
----
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