I. Basis of test
Only constituents can be moved.
Movement of some constituents is ungrammatical for independent reasons, so the test is most reliably used with grammatical sentences involving movement, rather than ungrammatical ones.
Constituents that cannot be moved:
(ii) A°, N°, P°, determiners:
* a friend good (whether N or A is moved)
* friend a (whether N or determiner is moved)
* just the top over (where P is moved)
III. Application to specific categories
Test sentence: John promised that he would finish his homework.
and [finish his homework] he will
* and [will finish his homework] he
(This example demonstrates that the modal is not part of VP; cf. the page on properties of INFL)
Test sentence: He likes [John's sister] very much.
[John's sister] he likes very much.
Test sentence: He went [down the river].
[Down the river] he went.
In the text above we refer to constituents of the type [determiner + noun] (e.g. the door) as NPs. In a more recent analysis, determiners are considered to be the head (D°) of a determiner phrase (DP), and the noun functions as its NP-complement.
For further information on DPs click here.