test/jdk/java/lang/StableValue/StableIntFunctionTest.java

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/* @test
 * @summary Basic tests for StableIntFunction methods
 * @enablePreview
 * @run junit StableIntFunctionTest
 */

import org.junit.jupiter.api.Test;

import java.util.concurrent.atomic.AtomicReference;
import java.util.function.IntFunction;

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

final class StableIntFunctionTest {

    private static final int SIZE = 2;
    private static final IntFunction<Integer> MAPPER = i -> i;

    @Test
    void factoryInvariants() {
        assertThrows(IllegalArgumentException.class, () -> StableValue.intFunction(-1, MAPPER));
        assertThrows(NullPointerException.class, () -> StableValue.intFunction(SIZE, null));
    }

    @Test
    void basic() {
        basic(MAPPER);
        basic(i -> null);
    }

    void basic(IntFunction<Integer> mapper) {
        StableTestUtil.CountingIntFunction<Integer> cif = new StableTestUtil.CountingIntFunction<>(mapper);
        var cached = StableValue.intFunction(SIZE, cif);
        assertEquals("[.unset, .unset]", cached.toString());
        assertEquals(mapper.apply(1), cached.apply(1));
        assertEquals(1, cif.cnt());
        assertEquals(mapper.apply(1), cached.apply(1));
        assertEquals(1, cif.cnt());
        assertEquals("[.unset, " + mapper.apply(1) + "]", cached.toString());
        assertThrows(IllegalArgumentException.class, () -> cached.apply(SIZE));
        assertThrows(IllegalArgumentException.class, () -> cached.apply(-1));
        assertThrows(IllegalArgumentException.class, () -> cached.apply(1_000_000));
    }

    @Test
    void exception() {
        StableTestUtil.CountingIntFunction<Integer> cif = new StableTestUtil.CountingIntFunction<>(_ -> {
            throw new UnsupportedOperationException();
        });
        var cached = StableValue.intFunction(SIZE, cif);
        assertThrows(UnsupportedOperationException.class, () -> cached.apply(1));
        assertEquals(1, cif.cnt());
        assertThrows(UnsupportedOperationException.class, () -> cached.apply(1));
        assertEquals(2, cif.cnt());
        assertEquals("[.unset, .unset]", cached.toString());
    }

    @Test
    void circular() {
        final AtomicReference<IntFunction<?>> ref = new AtomicReference<>();
        IntFunction<IntFunction<?>> cached = StableValue.intFunction(SIZE, _ -> ref.get());
        ref.set(cached);
        cached.apply(0);
        String toString = cached.toString();
        assertEquals("[(this StableIntFunction), .unset]", toString);
        assertDoesNotThrow(cached::hashCode);
        assertDoesNotThrow((() -> cached.equals(cached)));
    }

    @Test
    void equality() {
        IntFunction<Integer> f0 = StableValue.intFunction(8, MAPPER);
        IntFunction<Integer> f1 = StableValue.intFunction(8, MAPPER);
        // No function is equal to another function
        assertNotEquals(f0, f1);
    }

    @Test
    void hashCodeStable() {
        IntFunction<Integer> f0 = StableValue.intFunction(8, MAPPER);
        assertEquals(System.identityHashCode(f0), f0.hashCode());
        f0.apply(4);
        assertEquals(System.identityHashCode(f0), f0.hashCode());
    }

}