Answer by taking a quote from the following article:

Henry Hill, Jr. was born on June 11, 1943 in Manhattan, New York, to Henry Hill, Sr., an Irish immigrant and electrician, and Carmela Costa Hill, a Sicilian. The working-class family consisted of Henry and his eight siblings who grew up in Brownsville, a poorer area of the East New York section of Brooklyn. From an early age, Hill admired the local mobsters who socialized across the street from his home, including Paul Vario, a capo in the Lucchese crime family. In 1955, when Hill was 11 years old, he wandered into the cabstand across the street looking for a part-time after-school job.

Hill testified against his former associates to avoid a possible execution by his crew or going to prison for his crimes. His testimony led to 50 convictions.  Jimmy Burke was given 20 years in prison for the 1978-79 Boston College point shaving scandal, involving fixing Boston College basketball games. Burke was also later sentenced to life in prison for the murder of scam artist Richard Eaton. Burke died of lung cancer while serving his life sentence, on April 13, 1996, at the age of 64.  Paul Vario received four years for helping Henry Hill obtain a no-show job to get him paroled from prison. Vario was also later sentenced to ten years in prison for the extortion of air freight companies at JFK Airport. He died of respiratory failure on November 22, 1988, at age 73 while incarcerated in the FCI Federal Prison in Fort Worth.  Hill, his wife Karen, and their two children (Gregg and Gina) entered the U.S. Marshals' Witness Protection Program in 1980, changed their names, and moved to undisclosed locations in Omaha, Nebraska; Independence, Kentucky; Redmond, Washington; and Seattle, Washington. In Seattle, Hill hosted backyard cookouts for his neighbors, and on one occasion, while under the influence of a combination of liquor and drugs, he revealed his true identity to his guests. To the ire of the federal marshals, they were forced to relocate him one final time to Sarasota, Florida. There, a few months had passed, and Hill repeated the same breach of security, causing the government to finally expel him from the Federal Witness Protection Program.

What did he testify about?
Jimmy Burke was given 20 years in prison for the 1978-79 Boston College point shaving scandal, involving fixing Boston College basketball games.