Hi Dawid,

-Dtestpackage doesn't work anymore - is there some reason you didn't provide an 
alias, like you did for -Dtestmethod and -Dtestcase?

Steve

-----Original Message-----
From: Dawid Weiss [mailto:[email protected]] 
Sent: Sunday, April 15, 2012 10:45 AM
To: [email protected]
Subject: [Important] New test framework, differences, features, etc.

Ah... such a relief to finally have it committed even if this means the work 
has just begun on straightening it all out. So.

1) WHAT'S BEEN DONE?

The primary objective was to pull out "randomized" runner from Lucene and make 
it available as a separate project for reuse in other projects. This kind of 
grew into two things:

a) RandomizedRunner - a runner that has built-in support for randomization and 
other interesting features,
b) junit4-ant - an ANT task for running JUnit4 tests in parallel JVMs, with an 
aggregation of events, balancing, logs, different (from standard ANT) reporting 
and forked JVM crash resilience.

Everything above is heavily covered with unit tests (the code is on github 
here: https://github.com/carrotsearch/randomizedtesting).

LUCENE-3808 removes LuceneTestCaseRunner, replacing it with RandomizedRunner. 
It also modifies build scripts to run junit4-ant instead of ANT's default 
<junit>.

2) HOW DOES IT AFFECT ME AS A LUCENE/ SOLR DEVELOPER?

- The most visible change is that 'random' field in LuceneTestCase is gone. 
This change was motivated by the fact that the field's value was read from 
places where it shouldn't be read, passed to places where it shouldn't be 
passed, etc. Instead, the Random instance for a given scope (see below) can be 
acquired from a static method in LuceneTestCase called random(). In the 
essence, you can just add brackets around your previous random field references 
and it _should_ work out of the box. There are differences though: Random 
object returned by random() is valid only for the scope it was created for.
So any of the following will end up in an exception: saving a Random instance 
in a static scope (@BeforeClass) to a field and reusing it in a test, passing a 
Random instance from one thread to another, saving a Random instance to a field 
in one test, using it in another, etc. In
short: the result of random() is per-thread and only valid for the scope (test 
method, hook) it was acquired for. You _can_ call random() from non-test 
threads -- they will be given their own thread-local Random instances.

- The 'random seed' is a single HEX-encoded long. The "three seeds"
from before are gone. Everything is a derivative of the initial master seed.

- I provided a 'help on syntax' for test properties. Type:

ant test-help

and the most common use case scenarios will be dumped to your console.

- A notable difference is that 'tests.iter' property has been renamed to 
'tests.iters' (you'll get a build failure and a message if you try to use the 
former one). I could add a fallback but I'd rather not introduce any more 
aliases.

- "tests.iters" is no longer a poor-man's loop. It really re-runs a duplicate 
of a given test (or tests), including any @Before/@After hooks and setups. In 
theory, this means it is now possible to reiterate ANY test, no matter how 
complex. If it doesn't depend on static state, it can be repeated. This also 
links to how seed is used.
It's probably best explained on an example:

ant -Dtests.seed=deadbeef -Dtests.iters=3 -Dtestcase=TestSubScorerFreqs 
test-core

the above will result in 3 executions of every test in TestSubScorerFreqs. What 
you'll get on the console is:

   [junit4] <JUnit4> says hello. Random seed: deadbeef
   [junit4] Expected execution time on JVM J0:     0.02s
   [junit4] Executing 1 suite with 1 JVM.
   [junit4] Running org.apache.lucene.search.TestSubScorerFreqs
   [junit4] Tests run:   9, Failures:   0, Errors:   0, Skipped:   0,
Time:  0.45s
   [junit4]
   [junit4] JVM J0:     0.36 ..     0.96 =     0.60s
   [junit4] Execution time total: 0.98 sec.
   [junit4] Tests summary: 1 suite, 9 tests

and if you peek at the log file with test results
(build/core/test/tests-report.txt) you'll see the details of each executed test:

Executing 1 suite with 1 JVM.
Running org.apache.lucene.search.TestSubScorerFreqs
OK      0.04s | TestSubScorerFreqs.testTermQuery {#0
seed=[DEADBEEF:BAE943E3CC27A0F]}
OK      0.01s | TestSubScorerFreqs.testTermQuery {#1
seed=[DEADBEEF:BFF828C20800B123]}
OK      0.01s | TestSubScorerFreqs.testTermQuery {#2
seed=[DEADBEEF:3111BE1E59C4F9E8]}
OK      0.02s | TestSubScorerFreqs.testBooleanQuery {#0
seed=[DEADBEEF:3DDFB93BCC712A41]}
OK      0.01s | TestSubScorerFreqs.testBooleanQuery {#1
seed=[DEADBEEF:898905C7F8B3E16D]}
OK      0.01s | TestSubScorerFreqs.testBooleanQuery {#2
seed=[DEADBEEF:760931BA977A9A6]}
OK      0.01s | TestSubScorerFreqs.testPhraseQuery {#0
seed=[DEADBEEF:A7ADE8DE1DB7CA0B]}
OK      0.01s | TestSubScorerFreqs.testPhraseQuery {#1
seed=[DEADBEEF:13FB542229750127]}
OK      0.01s | TestSubScorerFreqs.testPhraseQuery {#2
seed=[DEADBEEF:9D12C2FE78B149EC]}
Tests run:   9, Failures:   0, Errors:   0, Skipped:   0, Time:  0.45s

Note that tests.iters=3 resulted in every test case executed three times, but 
they all count individually (so the reported total is 9 tests). What's also 
clearly seen is that the master seed is constant for all tests but each 
repetition gets a (predictable) derivative of the random seed. This way you can 
reiterate N times over a test, each time with a different seed. Now, compare 
this to:

ant -Dtests.seed=deadbeef:cafebabe -Dtests.iters=3 
-Dtestcase=TestSubScorerFreqs test-core

The log file now will be:

Executing 1 suite with 1 JVM.
Running org.apache.lucene.search.TestSubScorerFreqs
OK      0.04s | TestSubScorerFreqs.testTermQuery {#0 seed=[DEADBEEF:CAFEBABE]}
OK      0.01s | TestSubScorerFreqs.testTermQuery {#1 seed=[DEADBEEF:CAFEBABE]}
OK      0.01s | TestSubScorerFreqs.testTermQuery {#2 seed=[DEADBEEF:CAFEBABE]}
OK      0.02s | TestSubScorerFreqs.testBooleanQuery {#0
seed=[DEADBEEF:CAFEBABE]}
OK      0.01s | TestSubScorerFreqs.testBooleanQuery {#1
seed=[DEADBEEF:CAFEBABE]}
OK      0.01s | TestSubScorerFreqs.testBooleanQuery {#2
seed=[DEADBEEF:CAFEBABE]}
OK      0.01s | TestSubScorerFreqs.testPhraseQuery {#0 seed=[DEADBEEF:CAFEBABE]}
OK      0.01s | TestSubScorerFreqs.testPhraseQuery {#1 seed=[DEADBEEF:CAFEBABE]}
OK      0.01s | TestSubScorerFreqs.testPhraseQuery {#2 seed=[DEADBEEF:CAFEBABE]}
Tests run:   9, Failures:   0, Errors:   0, Skipped:   0, Time:  0.46s

We now fixed both the master and per-method seeds. Every repetition will have 
the same randomness. Test failures will report test error seeds as 
"master:test" so you will be able to use both scenarios, depending on the use 
case.

- "tests.iter.min" has been temporarily removed. I will think of a way to 
reintegrate it.

- The console output (sysout/systerrs) is only emitted to ANT's output if a 
test/suite fails. If a test/suite passes, its output is redirected in full to 
"tests-report.txt" file for inspection if needed.

3) WHAT ARE THE OTHER GOODIES?

There are many... For one thing, the console output will be much less chatty. 
Typically, one will see something like this:

   [junit4] <JUnit4> says hello. Random seed: 71F222160952E78A
   [junit4] Expected execution time on JVM J0:    93.93s
   [junit4] Expected execution time on JVM J1:    93.93s
   [junit4] Expected execution time on JVM J2:    93.93s
   [junit4] Expected execution time on JVM J3:    93.93s
   [junit4] Executing 296 suites with 4 JVMs.
   [junit4] Running org.apache.lucene.index.TestTermVectorsWriter
   [junit4] Tests run:  13, Failures:   0, Errors:   0, Skipped:   0,
Time:  1.31s
   [junit4]
   [junit4] Running org.apache.lucene.index.TestStressIndexing2
   [junit4] Tests run:   3, Failures:   0, Errors:   0, Skipped:   0,
Time:  1.89s
...

The number of JVMs used depends on your number of cores (and is not equal to 
their number to leave some room for infrastructure). ant test-help contains 
instructions how to override the number of JVMs to make the executions 
sequential, for example.

Another thing is that tests (their suite, output, etc.) that _failed_ are 
appended to tests-failures.txt. I remember that somebody once complained that 
it's impossible to find a test failure in ANT's log.
Now it should be easier. I made a test fail; the output is like this
(console):

   [junit4] Running org.apache.lucene.search.TestSubScorerFreqs
   [junit4] FAILURE 0.06s | TestSubScorerFreqs.testBooleanQuery
   [junit4]    > Throwable #1: java.lang.AssertionError
   [junit4]    >        at
__randomizedtesting.SeedInfo.seed([B2258B2DE68D190A:8FFA3216F4518DA4]:0)
   [junit4]    >        at org.junit.Assert.fail(Assert.java:92)
   [junit4]    >        at org.junit.Assert.fail(Assert.java:100)
   [junit4]    >        at
org.apache.lucene.search.TestSubScorerFreqs.testBooleanQuery(TestSubScorerFreqs.java:156)
....[snip]
   [junit4]    >
   [junit4]   2> NOTE: reproduce with: ant test
-Dtests.class=*.TestSubScorerFreqs
-Dtests.filter.method=testBooleanQuery -Dtests.seed=B2258B2DE68D190A 
-Dargs="-Dfile.encoding=Cp1252"
   [junit4]   2> NOTE: reproduce with: ant test
-Dtests.filter=*.TestSubScorerFreqs
-Dtests.filter.method=testBooleanQuery -Dtests.seed=B2258B2DE68D190A 
-Dargs="-Dfile.encoding=Cp1252"
   [junit4]   2>
   [junit4]    > (@AfterClass output)
   [junit4]   2> NOTE: test params are: codec=Lucene40:
{f=PostingsFormat(name=MockSep)}, sim=DefaultSimilarity, locale=da, 
timezone=Asia/Bishkek
   [junit4]   2> NOTE: all tests run in this JVM:
   [junit4]   2> [TestSubScorerFreqs, TestSubScorerFreqs]
   [junit4]   2> NOTE: Windows 7 6.1 amd64/Oracle Corporation 1.7.0_03
(64-bit)/cpus=8,threads=1,free=97723464,total=128647168
   [junit4]   2>
   [junit4] Tests run:   3, Failures:   1, Errors:   0, Skipped:   0,
Time:  0.45s <<< FAILURES!

Note "<<< FAILURES!" -- this is something to grep for. The " >" marker is a 
stack trace from the throwable, "2>" is standard error, "1>" is standard 
output. The same error is also appended to tests-failures.txt. The stack trace 
contains a synthetic entry with the master seed and the test's seed.

For those who prefer more visual (color) reports -- look for 
"tests-report-{module-name}" folder under the build folder. This contains 
index.html with a test report that should be easier to navigate around. An 
example of what such a report looks like is here:

http://builds.carrot2.org/browse/C2HEAD-SOURCES/latest/artifact/JOB1/JUnit-Test-Report/index.html

Yet another thing is that test suites are load-balanced across forked JVMs 
(with job stealing in place). For the initial balancing there are precomputed 
statistics (which should be updated from time to time!).
Any performance improvement this yields is currently eaten away by the cost of 
random() calls from tight loops in certain tests (it's better to just cache the 
result in a local variable). I'll try to pinpoint these later on. The timings 
shouldn't be much different to what it was before so it's not a performance 
drop.

I don't know what else... I'm sure there are things that I haven't covered. Ask 
if something is not clear or something is not working.

Dawid

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