Donald Trump claims he'll testify in hush money trial. We've heard that before.

• Donald Trump said Friday he plans to testify in his hush-money trial, set to start Monday.
• Trump previously backed out of testifying in his civil fraud trial. 
• The former president could open himself up to risky cross-examination if he testifies.

Former President Donald Trump on Friday said he will "absolutely" testify in his upcoming Manhattan hush-money trial, which is set to begin jury selection on Monday morning.

But Trump hasn't always kept his testimony promises.