IterateTest.java

package com.annimon.stream.intstreamtests;

import com.annimon.stream.IntStream;
import com.annimon.stream.function.IntPredicate;
import com.annimon.stream.function.IntUnaryOperator;
import org.junit.Test;
import static com.annimon.stream.test.hamcrest.IntStreamMatcher.assertElements;
import static org.hamcrest.Matchers.arrayContaining;
import static org.junit.Assert.assertTrue;

public final class IterateTest {

    @Test
    public void testStreamIterate() {
        IntUnaryOperator operator = new IntUnaryOperator() {
            @Override
            public int applyAsInt(int operand) {
                return operand + 1;
            }
        };

        assertTrue(IntStream.iterate(1, operator).limit(3).sum() == 6);
        assertTrue(IntStream.iterate(1, operator).iterator().hasNext());
    }

    @Test(expected = NullPointerException.class)
    public void testStreamIterateNull() {
        IntStream.iterate(0, null);
    }

    @Test
    public void testStreamIterateWithPredicate() {
        IntPredicate condition = new IntPredicate() {
            @Override
            public boolean test(int value) {
                return value < 20;
            }
        };
        IntUnaryOperator increment = new IntUnaryOperator() {
            @Override
            public int applyAsInt(int t) {
                return t + 5;
            }
        };
        IntStream.iterate(0, condition, increment)
                .custom(assertElements(arrayContaining(
                        0, 5, 10, 15
                )));
    }
}