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Re: [Qemu-block] [Qemu-devel] [PATCH v2] qemu-iotests: add a "how to" to

From: John Snow
Subject: Re: [Qemu-block] [Qemu-devel] [PATCH v2] qemu-iotests: add a "how to" to ./README
Date: Tue, 25 Jul 2017 12:25:55 -0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1

On 07/25/2017 11:36 AM, Stefan Hajnoczi wrote:
There is not much getting started documentation for qemu-iotests.  This
patch explains how to create a new test and covers the overall testing

Cc: Ishani Chugh <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
  * Added missing "touch <test-number>.out" step [Kevin]
  * Added reference to SubmitAPatch wiki page [Eric & Philippe]
  tests/qemu-iotests/README | 94 +++++++++++++++++++++++++++++++++++++++++++++++
  1 file changed, 94 insertions(+)

diff --git a/tests/qemu-iotests/README b/tests/qemu-iotests/README
index 6079b401ae..245f509b14 100644
--- a/tests/qemu-iotests/README
+++ b/tests/qemu-iotests/README
@@ -14,8 +14,102 @@ Just run ./check to run all tests for the raw image format, 
or ./check
  -qcow2 to test the qcow2 image format.  The output of ./check -h explains
  additional options to test further image formats or I/O methods.
+* Testing approach
+Each test is an executable file (usually a bash script) that is run by the
+./check test harness.  Standard out and standard error are captured to an
+output file.  If the output file differs from the "golden master" output file
+for the test then it fails.
+Tests are simply a sequence of commands that produce output and the test itself
+does not judge whether it passed or failed.  If you find yourself writing
+checks to determine success or failure then you should rethink the test and
+rely on output diffing instead.
+** Filtering volatile output
+When output contains absolute file paths, timestamps, process IDs, hostnames,
+or other volatile strings, the diff against golden master output will fail.
+Such output must be filtered to replace volatile strings with fixed
+For example, the path to the temporary working directory changes between test
+runs so it must be filtered:
+  sed -e "s#$TEST_DIR/#TEST_DIR/#g"
+Commonly needed filters are available in ./common.filter.
+** Python tests
+Most tests are implemented in bash but it is difficult to interact with the QMP
+monitor.  A Python module called 'iotests' is available for tests that require
+JSON and interacting with QEMU.
+* How to create a test
+1. Choose an unused test number
+Tests are identified by a unique number.  Look for the highest test case number
+by looking at the test files.  Then search the address@hidden mailing
+list to check if anyone has already sent patches using the next available
+number.  You may need to increment the number a few times to reach an unused
+2. Create the test file
+Copy an existing test (one that most closely resembles what you wish to test)
+to the new test number:
+  cp 001 <test-number>
+3. Assign groups to the test
+Add your test to the ./group file.  This file is the index of tests and assigns
+them to functional groups like "rw" for read-write tests.  Most tests belong to
+the "rw" and "auto" groups.  "auto" means the test runs when ./check is invoked
+without a -g argument.
+Consider adding your test to the "quick" group if it executes quickly (<1s).
+This group is run by "make check-block" and is often included as part of build
+tests in continuous integration systems.
+4. Write the test
+Edit the test script.  Look at existing tests for examples.
+5. Generate the golden master file
+Create an empty golden master file:
+  touch <test-number>.out
+Then run your test:
+  ./check <test-number>
+You may need additional command-line options to use an image format or
+protocol like -qcow2.
+The test will fail because there is no golden master yet.  Inspect the output
+that your test generated with "cat <test-number>.out.bad".
+Verify that the output is as expected and contains no volatile strings like
+timestamps.  You may need to add filters to your test to remove volatile
+Once you are happy with the test output it can be used as the golden master
+with "mv <test-number>.out.bad <test-number>.out".  Rerun the test to verify
+that it passes.
+Congratulations, you've created a new test!
+To contribute your test to qemu.git please follow the guidelines here:
  * Feedback and patches
Please send improvements to the test suite, general feedback or just
  reports of failing tests cases to address@hidden with a CC:
  to address@hidden


Unfortunately this does highlight how ridiculous our test number procurement process is, but at least it's documented.

Reviewed-by: John Snow <address@hidden>

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