Without knowing what they're running in the drill string I...

Without knowing what they're running in the drill string I imagine they'll have some sort of Measurement whilst drilling tools (MWD) and FEWD (formation evaluation whilst drilling ie gamma and resistivity at a minimum) to pick up on the lithology and indicate hydrocarbon presence (resistivity tool). This is performed as the tools run past the zone of interest and are integral to the BHA (bottom hole assembly) Then if it looks prospective they'll run an RFT (repeat formation test with the likes of a Schlumberger) to ascertain the fluids (Gas Oil or Water) that are present and analyze them.

Should the first well come up trumps then they'd look at drilling some development wells to test the extent of the geological structure.

No point drilling a hole if you can't collect any data. Also along the way they'll no doubt be collecting formation samples via "mudlogging" and be measuring any gas that comes up in the "mud" system (drilling fluids).

If there's any presence of hydrocarbons they will definitely test the well, by what means they do this though will be part of the pre designed drilling program.