public static void Y2015_Day19_GetPossibleMolecules()
{
// Arrange
string molecule = "HOH";
List <string> replacements = new() { "H => HO", "H => OH", "O => HH" };
// Act
var actual = Day19.GetPossibleMolecules(molecule, replacements, CancellationToken.None);
// Assert
actual.ShouldNotBeNull();
actual.ShouldBe(new[] { "HHHH", "HOHO", "HOOH", "OHOH" });
}