form.is_valid（）在Django单元测试中失败

我正在为Django表单运行单元测试，

form.is\u valid（）

不断返回

False

，我找不到错误

下面是forms.py的代码：

class CustomClearableFileInput(forms.ClearableFileInput):
    template_name = 'forums/templates/clearable_file_input.html'

class NewQuestionForm(forms.ModelForm):

    category = forms.ModelChoiceField(widget = forms.Select(attrs = {}),
                        queryset = FossCategory.objects.order_by('name'),
                        empty_label = "Select a Foss category",
                        required = True,
                        error_messages = {'required':'Select a category'})

    title = forms.CharField(widget = forms.TextInput(),
                        required = True,
                        error_messages = {'required':'Title field required'},
                        strip=True)

    body = forms.CharField(widget = forms.Textarea(),
                        required = True,
                        error_messages = {'required':'Question field required'},
                        strip=True)

    is_spam = forms.BooleanField(required = False)

    spam_honeypot_field = HoneypotField()

    image = forms.ImageField(widget = CustomClearableFileInput(), help_text = "Upload image", required = False)

    def clean_title(self):
        title = str(self.cleaned_data['title'])

        if title.isspace():
            raise forms.ValidationError("Title cannot be only spaces")
        if len(title) < 12:
            raise forms.ValidationError("Title should be longer than 12 characters")
        if Question.objects.filter(title = title).exists():
            raise forms.ValidationError("This title already exist.")

        return title

    def clean_body(self):

        body = str(self.cleaned_data['body'])
        if body.isspace():
            raise forms.ValidationError("Body cannot be only spaces")
        if len(body) < 12:
            raise forms.ValidationError("Body should be minimum 12 characters long")
        body = body.replace('&nbsp;', ' ')
        body = body.replace('<br>', '\n')

        return body

    class Meta(object):

        model = Question
        fields = ['category', 'title', 'body', 'is_spam', 'image']

这是我通过

打印（form.errors）

得到的：

类别
选择有效选项。该选项不是可用选项之一。

由于它是一个模型选择字段，请尝试使用类别的主键，而不是实例本身

form = NewQuestionForm(data = {'category': category.pk, 'title': title, 'body': 'Test question body'})

---

检查

form.errors

以查看其无效原因。我已用收到的错误更新了我的问题。我意识到了我的错误，并准备添加答案，但是的，这就是问题所在。非常感谢！：）

<ul class="errorlist"><li>category<ul class="errorlist"><li>Select a valid choice. That choice is not one of the available choices.</li></ul></li>

form = NewQuestionForm(data = {'category': category.pk, 'title': title, 'body': 'Test question body'})