Ungrammatical sentences for optional complementizer

regression_tests
grammar_matrix

#1

What would be some tests for overgeneration for a grammar that uses an optional complementizer to mark a clausal complement?

Examples of grammatical sentences (assume SVO order, which in itself is not what we are testing here):

subject knows that subject2 took object
subject knows subject2 took object

What kind of ungrammatical combinations could I use here?


#2

How about:

subject knows that that subject2 took object
subject knows subject2 took object that


#3

And maybe:

that subject took object