Run Tests

• Collapse your :dev and :nREPL aliases into one.

  There would be many similarities between :dev, :nREPL, and a hypothetical :test alias. Because we aren't relying on :main-opts there isn't much downside to just using one :dev alias.

  {:paths ["src"]
   :deps {org.clojure/clojure {:mvn/version "1.12.3"}
          ring/ring {:mvn/version "1.15.3"}
          metosin/reitit-ring {:mvn/version "0.9.2"}
          org.clojure/tools.logging {:mvn/version "1.3.0"}
          org.slf4j/slf4j-simple {:mvn/version "2.0.17"}
          hiccup/hiccup {:mvn/version "2.0.0"}}
   :aliases {:dev {:extra-paths ["dev"]
                   :extra-deps {nrepl/nrepl {:mvn/version "1.5.1"}}}
             :format {:deps {dev.weavejester/cljfmt {:mvn/version "0.15.3"}}}
             :lint   {:deps {clj-kondo/clj-kondo {:mvn/version "2025.10.23"}}}}}

  This does mean you will need to update how just nrepl functions slightly.

  help:
      just --list
  
  run:
      clojure -M -m example.main
  
  nrepl:
      clojure -M:dev -m nrepl.cmdline
  
  ...

• Add kaocha and a new test folder to your :dev alias

  Kaocha is a test runner. It runs your tests. The test folder is to have a place to write those tests.

  {:paths ["src"]
   :deps {org.clojure/clojure {:mvn/version "1.12.3"}
          ring/ring {:mvn/version "1.15.3"}
          metosin/reitit-ring {:mvn/version "0.9.2"}
          org.clojure/tools.logging {:mvn/version "1.3.0"}
          org.slf4j/slf4j-simple {:mvn/version "2.0.17"}
          hiccup/hiccup {:mvn/version "2.0.0"}}
   :aliases {:dev {:extra-paths ["dev" "test"]
                   :extra-deps {nrepl/nrepl {:mvn/version "1.5.1"}
                                lambdaisland/kaocha {:mvn/version "1.91.1392"}}}
             :format {:deps {dev.weavejester/cljfmt {:mvn/version "0.15.3"}}}
             :lint   {:deps {clj-kondo/clj-kondo {:mvn/version "2025.10.23"}}}}}

• Put the following in test/example/math_test.clj

  (ns example.math-test
    (:require [clojure.test :as t]))
  
  (t/deftest one-plus-one
    (t/is (= (+ 1 1) 3) "One plus one equals 3!"))

• Add a test recipe to your Justfile

  help:
      just --list
  
  run:
      clojure -M -m example.main
  
  nrepl:
      clojure -M:dev -m nrepl.cmdline
  
  format_check:
      clojure -M:format -m cljfmt.main check src dev
  
  format:
      clojure -M:format -m cljfmt.main fix src dev
  
  lint:
      clojure -M:lint -m clj-kondo.main --lint .
  
  test:
      clojure -M:dev -m kaocha.runner

• Run just test

  Because 1 + 1 does not equal 3, you should see a test failure reported.

• Fix your tests and run just test again

  (ns example.math-test
    (:require [clojure.test :as t]))
  
  (t/deftest one-plus-one
    (t/is (= (+ 1 1) 2) "One plus one equals 2!"))

• Add test to the list of directories to automatically format.

  help:
      just --list
  
  run:
      clojure -M -m example.main
  
  nrepl:
      clojure -M:dev -m nrepl.cmdline
  
  format_check:
      clojure -M:format -m cljfmt.main check src dev test
  
  format:
      clojure -M:format -m cljfmt.main fix src dev test
  
  lint:
      clojure -M:lint -m clj-kondo.main --lint .
  
  test:
      clojure -M:dev -m kaocha.runner