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JUnit testing
Learn JUnit testing in Kotlin through a focused explanation, a dedicated topic-specific example, an engineering boundary, and a mastery check.
JUnit testing is an atomic Kotlin topic inside JVM and Tooling. The example uses the named construct directly so you can see its syntax, data flow, and observable behavior.
Read the code by locating the exact feature named JUnit testing, then trace the value before and after that feature runs. This lesson is intentionally isolated from neighboring topics: changing identifiers alone would not reproduce the same behavior because the construct itself is different.
Topic-specific example
fun add(a:Int,b:Int)=a+b
fun main(){ check(add(2,3)==5); println("passed") }For JUnit testing, test the boundary that makes the feature meaningful: invalid input, an empty value, a missing branch, lifecycle/cleanup, or a type/runtime constraint. Do not infer correctness only from the happy path.