As mentioned upthread, in the book "The Boardwalk Jungle" by Ovid DeMaris, the author speculates that the flattering 1984 WSJ article about Salvie Testa, which called him the "heir to the top job in the Philadelphia Mafia", said that "Testa was on the brink of controlling the city's Mafia" and "has consolidated his power, bringing many friends into the Mob" would not have pleased the preening and paranoid Scarfo.

In the book "The Plumber" by Joseph Salerno and Stephen Rivele, the WSJ article is also mentioned as a source of friction, along with the claim that shortly after the broken engagement, the Family bigshots met at a restaurant and got into a heated argument which ended with Scarfo throwing Testa out.

And then finally in the book "Blood and Honor" by George Anastasia, Caramandi confirms the essentially personal nature of the Testa murder, claiming that he knew as soon as he heard of Testa's spurning of Merlino's daughter that Testa was a dead man. According to Caramandi an immediate campaign of lies and shunning began to be directed at Testa. The author also believed that Scarfo didn't take much convincing by Merlino to agree to Testa's elimination as he may feared to have Testa and Merlino too close.

"When the snows fall and the white winds blow, the lone wolf dies but the pack survives."
Winter is Coming

Now this is the Law of the Jungle—as old and as true as the sky; And the wolf that shall keep it may prosper, but the wolf that shall break it must die.
As the creeper that girdles the tree-trunk, the Law runneth forward and back; For the strength of the Pack is the Wolf, and the strength of the Wolf is the Pack.