integrations-tests: Amends README with instructive information

integration-tests/README.md

@@ -1,20 +1,24 @@
 # Integration tests against corpora
 
 This folder serves as playground for tests of basic functionality against many
-XML documents, mostly TEI-encodings. They are supposed to be executed with
+XML documents, mostly TEI encodings. They are supposed to be executed with
 major code change proposals and before releases.
 
 ## Test corpus
 
 Place document collections into the `corpora` folder. The `fetch-corpora.py`
-script helps to get going with the minimal requirement (~3GB) of tests.
+script helps to get going with the minimal requirement (~6GB) of data.
+Set any non-empty string as environment variable `SKIP_EXISTING` to skip
+downloading a corpus whose target folder already exists.
 
 Due to the `lb` tag [issue](https://github.com/deutschestextarchiv/dtabf/issues/33)
 with the DTABf the DTA corpus isn't considered. It could be an experiment to
 use *delb* for transformations with regards to the conclusions of that issue.
 
 The `normalize-corpora.py` script addresses issues that were found in the text
-encodings and must be run before the tests.
+encodings and must be run after fetching test data.
+One of the corpus folder names can be passed as argument to the script in order
+to process only this one's contents.
 
 ## Tests
 
@@ -25,3 +29,8 @@ reserves a `report.txt` for messages redirected from *stdout*.
 
 When problems occur, carefully investigate that it's not due to the source, and
 if not extract simple enough cases for the unit tests.
+
+## TODO
+
+After adding the third kind of test, wrap all scripts here into a
+[textual](https://textual.textualize.io) app.