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Add tests for when-let #808

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Add tests for when-let #808

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91fbdf2
Add tests for when-let.
alysbrooks Nov 16, 2025
9f0091b
Add test for when-let returning too many forms.
alysbrooks Nov 19, 2025
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37 changes: 37 additions & 0 deletions test/clojure/core_test/when_let.cljc
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Original file line number Diff line number Diff line change
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(ns clojure.core-test.when-let
(:require [clojure.test :as t :refer [deftest testing is are]]
[clojure.core-test.portability #?(:cljs :refer-macros :default :refer) [when-var-exists]]))

(when-var-exists when-let
(deftest test-when-let
(testing "basic single-binding tests using vectors or nil"
(is (= [0 1 2 3 4] (when-let [x [0 1 2 3 4] ] x)))
(is (not (nil? (when-let [x [nil]] x))))
(is (= [] (when-let [x []] x)))
(is (nil? (when-let [x nil] x))))
(testing "basic single-binding tests using seqs"
(is (= '(0 1 2 3 4) (when-let [x (range 5)] x))))
(testing "seq is only called once"
(let [calls (atom 0)
seq-fn (fn s [] (lazy-seq
(swap! calls inc)
(cons 1 (s))))
s (take 5 (seq-fn))]
(is (= '(1 1 1 1 1) (when-let [x s] x)))
(is (= @calls 5))))
(testing "without a body, truth doesn't matter"
(is (nil? (when-let [x nil])))
(is (nil? (when-let [x [false]])))
(is (nil? (when-let [x [true]]))))
(testing "when has an implicit `do`"
(let [counter (atom 0)]
(is (= :bar (when-let [x (range 5)]
(swap! counter inc)
(swap! counter inc)
(swap! counter inc)
:bar)))
(is (= 3 @counter))))
(testing "when-let accepts exactly two"
(is (thrown? Exception
(macroexpand
'(when-let [x (range 5) y (range 5)])))))))
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