I mean this is the book definition of him going on a rant.

Or by definition: To express at length a complaint or negative opinion

In a step his office says is unprecedented, Sen. Cory Booker (D., N.J.) will testify against fellow Sen. Jeff Sessions Wednesday when the Alabama Republican, nominated to become U.S. Attorney General, comes before the Senate Judiciary Committee.

"I do not take lightly the decision to testify against a Senate colleague. But the immense powers of the Attorney General combined with the deeply troubling views of this nominee is a call to conscience," Booker said in a statement issued by his office Monday night. "Sen. Sessions' decades-long record is concerning in a number of ways, from his opposition to bipartisan criminal justice reform to his views on bipartisan drug policy reform, from his efforts earlier in his career to deny citizens voting rights to his criticism of the Voting Rights Act, from his failure to defend the civil rights of women, minorities, and LGBT Americans to his opposition to common sense, bipartisan immigration reform. The Attorney General is responsible for ensuring the fair administration of justice, and based on his record, I lack confidence that Senator Sessions can honor this duty."

Booker's office, citing the Senate historian, said there is no record of a senator testifying against a fellow senator at a confirmation hearing.