Clojurians Log v2

You can move the handler creation to its own function, and then use a fixture (see (https://clojuredocs.org/clojure.test/use-fixtures) to call that function before running the namespace tests

but how can I pass data from a fixture to the test?

Ok, so there are two possible approaches. If you want to use the same handler in different deftest functions, you want to keep the handler in a top-level var. E.g., you could create an atom to hold all the handlers (and other system elements) that you want to use in several deftests. You add/remove them in your fixture, and access (use) them in our tests through the atom. This is a skeleton of this idea (might have slight errors, I didn't test it in the REPL):

(def system (atom {}))

(defn init-handler []
  (ig/init-key :delme.handler/example {}))

(defn halt-handler [system]
  (ig/halt-key! system))

(defn init-halt-handler [f]
  (reset! system (init-handler))
  (f)
  (halt-handler @system))

(use-fixtures :once init-halt-handler)

(deftest smoke-test
  (let [handler (:delme.handler/example @system)
   ....))

(deftest another-smoke-test
  (let [handler (:delme.handler/example @system)
   ....))

(deftest even-another-smoke-test
  (let [handler (:delme.handler/example @system)
   ....))

clj

(deftest smoke-test
  (let [handler (ig/init-key :delme.handler/example {})]
    (testing "example page exists"
      (let [response (handler (mock/request :get "/example"))]
        (is (= 200 (:status response)) "response ok")))
    (testing "example2 page exists"
      (let [response (handler (mock/request :get "/example2"))]
        (is (= 200 (:status response)) "response ok")))

    ;; More `testing` blocks here...

    (testing "example3 page does not exist"
      (let [response (handler (mock/request :get "/example3"))]
        (is (= 404 (:status response)) "page not found")))))