POSITIVE — the plot contains exactly what was given to it
  ok    point count in == point count plotted        5
  ok    x range preserved                            (0.0, 4.0)
  ok    y range preserved                            (5.0, 40.0)
  ok    final point not dropped/sorted               (4.0, 5.0)

POSITIVE — anti-truncation policy holds
  ok    y-axis includes zero by default              True

NEGATIVE — truncation is possible but must be ASKED for
  ok    explicit truncate_y raises the floor         True

NEGATIVE — refuses a false expectation
  ok    a false point count (99) is refused          False

POSITIVE — an output file is actually produced
  ok    png written and non-empty                    True

  transfer standard: matplotlib 3.10.8
  PROVEN — 8 checks, 0 failed