Java/src/test/java/com/thealgorithms/maths/CollatzConjectureTest.java

package com.thealgorithms.maths;

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

import java.util.List;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;

class CollatzConjectureTest {

    static CollatzConjecture cConjecture;

    @BeforeAll
    static void setUp() {
        cConjecture = new CollatzConjecture();
    }

    @Test
    void nextNumberFromEvenNumber() {
        assertEquals(25, cConjecture.nextNumber(50));
    }

    @Test
    void nextNumberFromOddNumber() {
        assertEquals(154, cConjecture.nextNumber(51));
    }

    @Test
    void collatzConjecture() {
        final List<Integer> expected = List.of(
            35,
            106,
            53,
            160,
            80,
            40,
            20,
            10,
            5,
            16,
            8,
            4,
            2,
            1
        );
        assertIterableEquals(expected, cConjecture.collatzConjecture(35));
    }

    @Test
    void sequenceOfNotNaturalFirstNumber() {
        assertThrows(
            IllegalArgumentException.class,
            () -> cConjecture.collatzConjecture(0)
        );
        assertThrows(
            IllegalArgumentException.class,
            () -> cConjecture.collatzConjecture(-1)
        );
    }
}