
    it "sets the weight correctly" $ do
      let rope = Node 11 (Leaf "hello ") (Leaf "world")
      (length' $ insert rope 5 " wicked") `shouldBe` length "hello wicked world"
      (length' $ insert rope 9 "d go") `shouldBe` length "hello word gold"
      (length' $ insert rope 6 "great ") `shouldBe` length "hello great world"

    it "stress tests" $ do
      let r1 = Leaf "hello"
      let r2 = insert r1 5 " world"
      let r3 = insert r2 5 " wicked"
      let r4 = insert r3 0 "well, "
      let r5 = insert r4 24 "."

      toString r5 `shouldBe` "well, hello wicked world."