How to approach copying a schema for testing?
The 12c Multitenant option is a nice tool for this.

Create a "master" pluggable database that is your starting point, and you can create other pluggable databases by cloning this PDB.

When you clone a PDB, you have the option to clone the PDB as a "snapshot copy". This does not actually copy the files, but uses storage snapshots, and that is what makes this feature great. For example, cloning a 111 GB database took 20 seconds in this example: Snapshot clone of a PDB using ACFS

When I experimented with it, smaller databases took even less time to be cloned. When you do not need the database anymore, you can just simply drop it.

Also you are not limited to 1 schema, because you can create many clones and use them at the same time concurrently, up to 252 PDBs.

Note that, the Multitenant option is an extra cost option for Enterprise Edtition databases. So you need the proper license to use it.

SNAPSHOT COPY