unit-testing - Clojure.spec:基于生成器中其他字段的字段存在

Question

假设我们有 API 可以将不同类型的文件属性保存到 DB* 中:文本、图像、音频和视频文件。它应该能够根据其类型获取以下字段:
所有文件的基本属性:

{"file-type": "text",
"location": "/Documents",
"creation-time": "2020-03-02",
"name": "sometext.txt"}

仅针对某些类型的附加 Prop :

text: only base props
video file: base props + {"duration(s)":123, "resolution":"4k"}
audio file: base props + {"duration(s)":123}
image: base props + {"resolution":"2048x1536"}

正如我们所看到的，某些字段应该为零取决于“文件类型”。
假设我们需要验证这种输入，它可以是所描述的任何类型。
所以规范是:

(s/def ::file-type (s/with-gen (s/and string? not-empty) #(s/gen #{"text" "image" "video" "audio"})))
(s/def ::location (s/with-gen (s/and string? not-empty) #(s/gen #{"/Documents"})))
(s/def ::creation-time (s/with-gen (s/and string? not-empty) #(s/gen #{"2020-03-02"}))) ;for simplicity
(s/def ::name (s/with-gen (s/and string? not-empty) #(s/gen #{"sometext.txt" "image.jpg" "video.mp4" "audio.mp3"}))) ;for simplicity
(s/def ::duration (s/and int? not-empty))                   ;for simplicity
(s/def ::resolution (s/with-gen (s/and string? not-empty) #(s/gen #{"4k" "2048x1536"}))) ;for simplicity
(s/def ::files-input (s/keys :req-un [::file-type ::location ::creation-time ::extension] :opt-un [::duration ::resolution]))

假设有一个程序化验证器可以检查为每种文件类型传递的正确字段集(例如，“video”有“duration”字段，但“text”没有)。
问题是:如何 生成 完整的现成 具有这些依赖项的输入 用于单元测试(包括依赖字段)？

*(让我们抛开这个问题是否是 API 的正确设计，因为这个例子不是来自现实生活，仅用于演示目的)

Answer 1

基于 multi-spec doc ，我们必须为每种情况添加具有自己的字段集的单独方法:

(s/def ::file-type (s/with-gen (s/and string? not-empty) #(s/gen #{"text" "image" "video" "audio"})))
(s/def ::location (s/with-gen (s/and string? not-empty) #(s/gen #{"/Documents"})))
(s/def ::creation-time (s/with-gen (s/and string? not-empty) #(s/gen #{"2020-03-02"}))) ;for simplicity
(s/def ::name (s/with-gen (s/and string? not-empty) #(s/gen #{"sometext.txt" "image.jpg" "video.mp4" "audio.mp3"}))) ;for simplicity
(s/def ::duration pos-int?)                                 ;for simplicity
(s/def ::resolution (s/with-gen (s/and string? not-empty) #(s/gen #{"4k" "2048x1536"}))) ;for simplicity
(s/def ::base-props (s/keys :req-un [::file-type ::location ::creation-time ::name]))
(s/def ::file-type-key (s/with-gen keyword? #(s/gen #{:text :image :video :audio})))

(defmulti file :file-type-key)
(defmethod file :text [_]
    (s/merge (s/keys :req-un [::file-type-key]) ::base-props))
(defmethod file :image [_]
    (s/merge (s/keys :req-un [::file-type-key ::resolution]) ::base-props))
(defmethod file :video [_]
    (s/merge (s/keys :req-un [::file-type-key ::duration ::resolution]) ::base-props))
(defmethod file :audio [_]
    (s/merge (s/keys :req-un [::file-type-key ::duration]) ::base-props))
(defmethod file :default [_]
    (s/merge (s/keys :req-un [::file-type-key]) ::base-props))

(s/def ::file-input (s/and (s/multi-spec file :file-type-key)
                           (fn [{:keys [file-type file-type-key]}]
                               (= file-type-key (keyword file-type)))))

将为单元测试提供生成的输入(可通过 stest/check 检查):

(gen/sample (s/gen ::file-input) 2)
=>
({:file-type-key :text, :file-type "text", :location "/Documents", :creation-time "2020-03-02", :name "sometext.txt"}
 {:file-type-key :image,
  :resolution "4k",
  :file-type "image",
  :location "/Documents",
  :creation-time "2020-03-02",
  :name "sometext.txt"})

我们不得不再添加一个字段 ::file-type-key作为选择器(必须是关键字)，但不影响测试，可以是 dissoc轻松编辑。