// Lacking a worked example from the text, test using meeus/moonposition.
func TestPerigeeParallax(t *testing.T) {
got := apsis.PerigeeParallax(1997.93)
_, _, d := moonposition.Position(apsis.Perigee(1997.93))
want := moonposition.Parallax(d)
Δ := math.Abs((got - want).Sec())
// for this case anyway it's within a tenth of an arc second
if Δ > .1 {
t.Fatal("got", got, "want (about)", want)
}
}
// Test cases from p. 361.
func TestPerigee(t *testing.T) {
for _, c := range []struct {
y, m int
d, dy float64
}{
{1997, 12, 9 + 16.9/24, 1997.93},
{1998, 1, 3 + 8.5/24, 1998.01},
{1990, 12, 2 + 10.8/24, 1990.92},
{1990, 12, 30 + 23.8/24, 1991},
} {
ref := julian.CalendarGregorianToJD(c.y, c.m, c.d)
j := apsis.Perigee(c.dy)
if math.Abs(j-ref) > .1 {
t.Fatal("got", j, "expected", ref)
}
}
}