Major Description
The lucene-test-framework test dependency must appear before lucene-core in the test classpath, to allow test-only read/write PreFlexRWCodec to fulfill Lucene3x codec requests instead of lucene-core's read-only Lucene3xCodec.
SOLR-2849 refactored Solr dependencies and pulled the lucene-test-framework test dependency into the solr-parent POM, and all Solr child POMs inherit that dependency. When a Solr child module e.g. solr-core runs tests under Maven, it orders the solr-parent dependencies after its own dependencies (see MNG-3494), and so lucene-test-framework will always appear after lucene-core if it is declared in the solr-parent POM. (I searched the interweb for a mechanism to influence this ordering, and came up empty-handed...)
Under LUCENE-3490 I committed a fix to the lucene/ and modules/ POMs, but not to any of Solr's POMs - I'm not sure why I excluded Solr at that point 
.
This misconfiguration triggered a test failure today in the Lucene-Solr-Maven-trunk Jenkins build for org.apache.solr.core.TestArbitraryIndexDir.testLoadNewIndexDir:
CheckIndex failed
Segments file=segments_1 numSegments=1 version=4.0 format=FORMAT_4_0 [Lucene 4.0]
1 of 1: name=_0 docCount=1
codec=Lucene3x
compound=false
FAILED
WARNING: fixIndex() would remove reference to this segment; full exception:
org.apache.lucene.index.IndexFormatTooNewException: Format version is not supported (resource: MockIndexInputWrapper(SimpleFSIndexInput(path="/usr/home/hudson/hudson-slave/workspace/Lucene-Solr-Maven-trunk/checkout/solr/build/solr-maven/test/org.apache.solr.core.TestArbitraryIndexDir-1326913332577/solr/data/index_temp/_0.fnm"))): -2147483648 (needs to be between -2 and -3)
at org.apache.lucene.codecs.lucene3x.Lucene3xFieldInfosReader.read(Lucene3xFieldInfosReader.java:71)
...
NOTE: reproduce with: ant test -Dtestcase=TestArbitraryIndexDir -Dtestmethod=testLoadNewIndexDir -Dtests.seed=2035db5097855cfe:-1d64b1ca3d5e4ac9:4163b1b8d4ca3ca0 -Dargs="-Dfile.encoding=ISO8859-1"
I was able to reproduce locally using the following cmdline from solr/core/:
mvn test -Dtest=TestArbitraryIndexDir -Dtests.seed=2035db5097855cfe:-1d64b1ca3d5e4ac9:4163b1b8d4ca3ca0 -Dfile.encoding=ISO8859-1
The fix is to move the lucene-test-framework dependency declaration out of the solr-parent POM and back into each of the Solr child POMs under which tests are run.