Clojure spec uses test.check internally to generate sample values. Here is how test.check can be overridden. Whenever trying to write unit tests with a "fake" function, with-redefs is your friend:
(ns tst.demo.core
(:use tupelo.core tupelo.test)
(:require
[clojure.test.check.generators :as gen]
))
(def id-gen gen/uuid)
(dotest
(newline)
(spyx-pretty (take 3 (gen/sample-seq id-gen)))
(newline)
(with-redefs [id-gen (gen/choose 1 5)]
(spyx-pretty (take 33 (gen/sample-seq id-gen))))
(newline)
)
with result:
-----------------------------------
Clojure 1.10.3 Java 15.0.2
-----------------------------------
Testing tst.demo.core
(take 3 (gen/sample-seq id-gen)) =>
[#uuid "cbfea340-1346-429f-ba68-181e657acba5"
#uuid "7c119cf7-0842-4dd0-a23d-f95b6a68f808"
#uuid "ca35cb86-1385-46ad-8fc2-e05cf7a1220a"]
(take 33 (gen/sample-seq id-gen)) =>
[5 4 3 3 2 2 3 1 2 1 4 1 2 2 4 3 5 2 3 5 3 2 3 2 3 5 5 5 5 1 3 2 2]
Example created
using my favorite template project.
Update
Unfortunately, the above technique does not work for Clojure Spec since (s/def ...) uses a global registery of Spec definitions, and is therefore immune to with-redefs. However, we can overcome this definition by simply redefining the desired spec in the unit test namespace like:
(ns tst.demo.core
(:use tupelo.core tupelo.test)
(:require
[clojure.spec.alpha :as s]
[clojure.spec.gen.alpha :as gen]
))
(s/def :app/id (s/int-in 9 99))
(s/def :app/name string?)
(s/def :app/cust (s/keys :req-un [:app/id :app/name]))
(dotest
(newline)
(spyx-pretty (gen/sample (s/gen :app/cust)))
(newline)
(s/def :app/id (s/int-in 2 5)) ; overwrite the definition of :app/id for testing
(spyx-pretty (gen/sample (s/gen :app/cust)))
(newline))
with result
-----------------------------------
Clojure 1.10.3 Java 15.0.2
-----------------------------------
Testing tst.demo.core
(gen/sample (s/gen :app/cust)) =>
[{:id 10, :name ""}
{:id 9, :name "n"}
{:id 10, :name "fh"}
{:id 9, :name "aI"}
{:id 11, :name "8v5F"}
{:id 10, :name ""}
{:id 10, :name "7"}
{:id 10, :name "3m6Wi"}
{:id 13, :name "OG2Qzfqe"}
{:id 10, :name ""}]
(gen/sample (s/gen :app/cust)) =>
[{:id 3, :name ""}
{:id 3, :name ""}
{:id 2, :name "5e"}
{:id 3, :name ""}
{:id 2, :name "y01C"}
{:id 3, :name "l2"}
{:id 3, :name "c"}
{:id 3, :name "pF"}
{:id 4, :name "0yrxyJ7l"}
{:id 4, :name "40"}]
So, it's a little ugly, but the redefinition of :app/id does the trick, and it only takes effect during unit test runs, leaving the main application unaffected.
