One of the available thing to you - is to check Lucene index files manually.
I suspect that the most important ones are the Term Dictionary files (*.tim)
I’ve indexed document with no stored values and terms - [email protected]
in field email (TextField with Standard analyzer) and John
in field name (StringField)
After this one, I opened tim file with hex editor and was able to see something like this:

You could clearly see the values of test, test, com
which were tokenized by Standard one, also you could see John still stays the same, since I used StringField. In my other examples, I was able to see the work of lowercasing as well.
Just a reminder, if you would like to repeat it - by default for small indices Lucene will put everything into compound file, which I don’t prefer for this specific debug. You could disable this by setUseCompoundFile(false)