public void ImproveNutrientInSoil() { ISoil soil = new Soil(); INutrient nitrogen = new Nutrient("Nitrogen"); soil.Absorb(nitrogen); Assert.True(soil.Nourishment(nitrogen) > 0); soil.Sterilize(); INutrient phosphorus = new Nutrient("Phosphorus"); soil.Absorb(phosphorus); Assert.True(soil.Nourishment(nitrogen) == 0); }