public void GetAllPlanTypes_ShouldReturnAllValidValues_UnderAllConditions()
{
// Arrange & Act
PlanType[] output = CUT.GetAllPlanTypes().ToArray();
// Assert
output.ShouldNotBeNull();
output.ShouldNotBeEmpty();
output.ShouldContain(PlanType.Fixed);
output.ShouldContain(PlanType.Variable);
output.ShouldContain(PlanType.Indexed);
}
