Fixed the output part of ContactManagerImpl! Writer was appending, not overwriting, so ended up with a lot of arraylists in contacts.txt. Opening a new writer every time I want to write is a bit of a long way round but it at least works.
Added tearDown() method to test class, with a call to flush() to close internal reader. Writing test for import of existing data
Wrote test to check that ContactManager can read from an existing contacts.txt and populate itself. Not yet working
Uncommented the section in the constructor of CM that reads from file.
Think I've fixed the file input but now all my other tests are failing.
Tests no longer failing - added call to delete contacts.txt in the test class tearDown() method. Moved a couple of lines of code around in ContactManagerImpl to avoid NullPointerException if inputStream is never assigned.