Contracts in Clojure: Settling Types vs Tests @jessitron What do - - PowerPoint PPT Presentation

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Contracts in Clojure: Settling Types vs Tests @jessitron What do - - PowerPoint PPT Presentation

Sep 06, 2023 426 likes •1.33k views

Contracts in Clojure: Settling Types vs Tests @jessitron What do we know? How do we know it? Informal Reasoning Formal Experimental Proofs Evidence // Scala def formatReport(data: ReportData): ExcelSheet types (defn format-report

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Contracts in Clojure:

Settling Types vs Tests

@jessitron

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What do we know? How do we know it?

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Informal Reasoning Formal Proofs Experimental Evidence

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def formatReport(data: ReportData): ExcelSheet // Scala

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types

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(defn format-report [report-data] …) format-report

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(function-name arg1 arg2)

function application

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(function-name arg1 arg2) (defn function-name [param1 param2] (println "Hello QCon") (do-something-with (and param1 param2)))

function definition last expression is the result

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(defn function-name [param1 param2] (println "Hello QCon") (do-something-with (and param1 param2)))

square braces make a vector

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(defn format-report [report-data] …) format-report

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(defn ad-performance-report [params] (-> (fetch-events params) (analyze-ad-performance params) format-report)) format-report

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(defn ad-performance-report [params] (-> (fetch-events params) (analyze-ad-performance params) format-report)) fetch-events

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…) (defn fetch-events [params] fetch-events

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{:when 12:34:56 7/8/90 :what "show" :who "abc123"}

curly braces make a map keyword

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{:when org.joda.time.DateTime :what java.lang.String :who java.lang.String} (def Event )

give a thing a name

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(def Event ) {:when DateTime :what s/Str :who s/Str} (:require [schema.core :as s])

dependency

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(def Event ) {:when DateTime :what Incident :who Customer} Event (def Incident s/Str) (def Customer s/Str)

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[Event] (def Event ) {:when DateTime :what Incident :who Customer}

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…) (defn fetch-events [params] [Event]

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[Event] (:require [schema.core :as s]) …) (s/defn fetch-events [params] :- [Event]

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(deftest fetch-events-test … (= (expected (fetch-events input))))

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(deftest fetch-events-test … (= (expected (fetch-events input)))) (use-fixtures schema.test/validate-schemas)

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(defn ad-performance-report [params] (-> (fetch-events params) (analyze-ad-performance params) format-report)) (d ) [Event] analyze-ad-performance

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(defn analyze-ad-performance [events params] (-> events (group-up params) summarize add-total-row (add-headers params))) analyze-ad-performance

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[Event] (defn analyze-ad-performance [events params] (-> events (group-up params) summarize add-total-row (add-headers params)))

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[[Event]] [Event] (defn analyze-ad-performance [events params] (-> events (group-up params) summarize add-total-row (add-headers params)))

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[[Event]] [Event] (defn analyze-ad-performance [events params] (-> events (group-up params) summarize add-total-row (add-headers params)))

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[[Event] ]

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[[Event] Summation]

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[( one [Event] ) ( one Summation )]

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[(s/one [Event] "event list") (s/one Summation "group sum")]

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{:groups [[(s/one [Event] "event list") (s/one Summation "group sum")]]}

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{:groups [[(s/one [Event] "event list") (s/one Summation "group sum")]] :total Totals}

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{:header Headers :groups [[(s/one [Event] "event list") (s/one Summation "group sum")]] :total Totals})

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(def ReportData {:header Headers :groups [[(s/one [Event] "event list") (s/one Summation "group sum")]] :total Totals})

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(s/defn analyze-ad-performance :- ReportData [events :- [Event] params :- Params] (-> events (group-up params) summarize add-total-row (add-headers params)))

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(s/defn analyze-ad-performance :- ReportData …)

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(s/defn analyze-ad-performance :- (at-least ReportData) …)

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(s/defn analyze-ad-performance :- (at-least ReportData) …) (defn at-least [map-schema] (merge map-schema {s/Any s/Any}))

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What do we know?

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What do we know?

data shape

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What do we know?

data shape value boundaries

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:title

  • string
  • not empty
  • capitalized

Headers

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(def Headers {:title (s/constrained s/Str (s/pred (complement empty?) "nonempty") (s/pred capitalized? "Title Caps")) …})

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What do we know?

data shape data value boundaries relationships within values

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What do we know?

data shape data value boundaries relationships within values

What could we know?

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What do we know?

data shape relationships within values

What could we know?

produced types data value boundaries

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(s/defn fetch-events :- [Event] [params] …) Seq[Event]

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(s/defn fetch-events :- [Event] [params] …)

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(st/defn fetch-events :+ (st/LazySeq Event) [params] …)

what if?

check this later

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(st/defn fetch-events :+ (st/LazySeq Event) [params] …) (:require [schematron.core :as st])

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(s/defn a-higher-order-function [predicate :- (s/=> Bool Event) …] …)

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(st/defn a-higher-order-function [predicate :+ (st/=> Bool Event) …] …)

what if?

check this later

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(s/defn a-higher-order-function :- Event [predicate :- (st/=> Bool Event) …] …)

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(st/defn [A] a-higher-order-function :- A [predicate :+ (st/=> Bool A) …] …)

what if?

(a-higher-order-function Event is-happy …)

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What do we know?

data shape data value boundaries relationships within values

What could we know?

produced types relationships between types relationships between values

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What do we know? What could we know?

produced types relationships between types relationships between values data shape relationships within values data value boundaries

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(defn group-up [events params] {:post [(as-lazy-as events %)] …))

postcondition

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produced types relationships between types relationships between values data shape relationships within values data value boundaries

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How do we know it?

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(deftest analyze-ad-performance-test (testing "grouping of rows" (let [… result (analyze-ad-performance events {}) (is (= expected (:groups result))))))

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(use-fixtures schema.test/validate-schemas) (deftest analyze-ad-performance-test (testing "grouping of rows" (let [… result (analyze-ad-performance events {}) (is (= expected (:groups result))))))

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(let [… result (analyze-ad-performance events {}) (is (= expected (:groups result))))))

Input does not match schema Params Missing required key :title Missing required key :start Missing required key :end

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(let [… result (analyze-ad-performance events (sc/complete {} Params) (is (= expected (:groups result))))))

"Fill in everything else with something random until it meets this schema"

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{:title "YhKEzII", :start "-217863493-11-21T00:54:39.872Z"], :end "-256417656-09-30T01:08:11.904Z"]} any string any date before now any date before the start

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(deftest analyze-ad-performance-test (testing "grouping of rows" (let [… result (analyze-ad-performance [events] (sample-one param-gen)) (is (= expected (:groups result)))))) (use-fixtures schema.test/validate-schemas)

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1 test is an anecdote generative tests are evidence

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?

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?

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?

Experimental Evidence

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(defspec analyze-ad-performance-spec 100 (for-all [events events-gen params param-gen] (analyze-ad-performance events params)))) (use-fixtures schema.test/validate-schemas)

(s/defn analyze-ad-performance :- ReportData …)

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What do we know? How do we know it? Schemas Generative Tests

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B A

Contract

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B A

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A A

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A B

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A B

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implementation schemas generators tests

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implementation schemas tests testkit client libs gen

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B A

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Science!

test.check prismatic/schema Clojure

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Science!

generative tests types and contracts … your language …

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Science!

testkits client libraries … your services …

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Informal Reasoning Formal Proofs Experimental Evidence

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@jessitron

blog.jessitron.com

https://github.com/jessitron/contracts-as-types-examples

examples resources

https://github.com/Prismatic/schema http://hintjens.com/blog:85 The End of Software Versions http://david-mcneil.com/post/114783282473/extending- prismatic-schema-to-higher-order https://github.com/jessitron/schematron http://dl.acm.org/citation.cfm?id=2661156 Static typing and productivity: Stefik & Hanenberg 2014