Testing method that returns relation model attribute

I have the following models:

class Course(Base):

    title = models.CharField('Título', max_length=200)
    subcategory = models.ForeignKey(SubCategory, on_delete=models.CASCADE)

    def get_category(self):
        return self.subcategory.category


class SubCategory(Base):
    title = models.CharField('Título', max_length=80)
    category = models.ForeignKey(Category, on_delete=models.CASCADE)


class Category(Base):
    title = models.CharField('Título', max_length=80)

How can I test the get_category method?

I'm trying to do that but the test don't pass on coverage report.