private Material createValidMaterial() {
MaterialCategory materialCategory = MaterialCategory.create(UUID.randomUUID().toString());
materialCategoryDAO.save(materialCategory);
UnitType unitType = UnitType.create("m");
unitTypeDAO.save(unitType);
Material material = Material.create(UUID.randomUUID().toString());
material.setDescription("material");
material.setCategory(materialCategory);
material.setUnitType(unitType);
materialDAO.save(material);
return material;
}