///usr/bin/env jbang "$0" "$@" ; exit $?

//JAVA 25+

//DEPS org.junit.jupiter:junit-jupiter-api:6.0.3

//DEPS org.jspecify:jspecify:1.0.0

import org.junit.jupiter.api.Test;

import org.jspecify.annotations.NullMarked;

import org.jspecify.annotations.Nullable;

import static org.junit.jupiter.api.Assertions.*;

/// Proof: junit6-with-jspecify

/// Source: content/tooling/junit6-with-jspecify.yaml

record User(String name) {}

interface UserService {

@Nullable User findById(String id);

}

UserService service = id -> id.equals("u1") ? new User("Alice") : null;

@NullMarked // all refs non-null unless @Nullable

class UserServiceTest {

// JUnit 6 API is @NullMarked:

// assertNull(@Nullable Object actual)

// assertEquals(@Nullable Object, @Nullable Object)

// fail(@Nullable String message)

@Test

void findUser_found() {

// IDE warns: findById returns @Nullable User

@Nullable User result = service.findById("u1");

assertNotNull(result); // narrows type to non-null

assertEquals("Alice", result.name()); // safe

}

@Test

void findUser_notFound() {

@Nullable User result = service.findById("missing");

assertNull(result); // IDE confirms null expectation

}

}

void main() {}