James Clark has a collection of test cases for testing XML parsers at http://www.jclark.com/xml/ which includes a conformance test.
Mary Brady, OASIS XML Conformance TC Chair, writes: A much larger and more comprehensive suite is the NIST/OASIS Conformance Test Suite, available from http://www.oasis-open.org/committees/xmltest/testsuite.htm, which contains contributions from James Clark, OASIS and NIST, Sun, and Fuji Xerox.
Carmelo Montanez writes: NIST has developed a number of XSLT/XPath tests, which will be part of the official OASIS XSLT/XPath suite (not yet released). These tests are available from our web site at http://xw2k.sdct.itl.nist.gov/xml/index.html (click on `XSL Testing' ). The expected output may be slightly different from one implementation to another. The OASIS XSLT technical committee has a solution for that problem, however our tests
do not yet implement such solution. Please forward any comments to firstname.lastname@example.org.
Jon Noring writes: For those who are interested, I took the current and complete Unicode 3.0 `cast' of characters and their hex codes, and created a simple XML document of it to test XML browsers for Unicode conformity. It is not finished yet--I need to add comments and to fix the display of rtl characters (ie Hebrew, Arabic). It is found at: http://www.windspun.com/unicode-test/unicode.xml. It is
quite large, almost 900K in size, so be prepared. IE5 renders many of the characters in this XML document--and for the ones it does render it appears to do so correctly. I look forward to when Opera will do likewise. I haven't tested the current version of Mozilla/Netscape for Unicode conformity.