Tests for Phrase Structure
 the existence of the syntactic constituents in tree structures can be verified
with the help of special tests
o not every test works for every constituent
The substitution test
 the substitution test confirms that a phrase is a unit by replacing it by a
single word:
if a group of words can be replaced by a single word such as there, they,
so, do, etc., it is a syntactic constituent
[The children] stopped [at the corner]PP.
We stopped [there] too.
at the corner = there
[They] waited for us to catch up.
the children = they
The children [will stop at the corner]VP,
if they see us [do so].
will stop at the corner
= do so
The movement test
 if a group of words can be moved as a single unit to a different position
within the sentence, they constitute a phrase
The children stopped [at the corner]PP.
[At the corner]PP, they stopped.
The coordination test
 if a group of words can be joined to another group of words by a conjunction
such as and, or, or but, they constitute a phrase
The children [stopped at the corner]VP and [looked both ways]VP.