PaginationHelperTest.java

package com.company.PaginationHelper;

import java.util.List;
import org.junit.jupiter.api.*;
import static org.junit.jupiter.api.Assertions.assertEquals;

@TestMethodOrder(MethodOrderer.OrderAnnotation.class)
class PaginationHelperTest {

    private List<Character> collection = List.of('a', 'b', 'c', 'd', 'e', 'f');
    private PaginationHelper<Character> helper = new PaginationHelper<>(collection, 4);

    @Test @Order(1) @DisplayName("Test pageCount()")
    void testPageCount() {
        assertEquals(2, helper.pageCount(), "pageCount is returning incorrect value");
    }

    @Test @Order(2) @DisplayName("Test itemCount()")
    void testItemCount() {
        assertEquals(6, helper.itemCount(), "itemCount is returning incorrect value");
    }

    @Test @Order(3) @DisplayName("Test pageItemCount()")
    void testPageItemCount() {
        assertEquals( 4, helper.pageItemCount(0), "pageItemCount is returning incorrect value for page 0");
        assertEquals( 2, helper.pageItemCount(1), "pageItemCount is returning incorrect value for page 1");
        assertEquals(-1, helper.pageItemCount(2), "pageItemCount is returning incorrect value for page 2");
        assertEquals(-1, helper.pageItemCount(-1), "pageItemCount is returning incorrect value for page -1");
    }

    @Test @Order(4) @DisplayName("Test pageIndex()")
    void testPageIndex() {
        assertEquals( 1, helper.pageIndex(5), "pageIndex is returning incorrect value for index 5");
        assertEquals( 0, helper.pageIndex(2), "pageIndex is returning incorrect value for index 2");
        assertEquals(-1, helper.pageIndex(20), "pageIndex is returning incorrect value for index 20");
        assertEquals(-1, helper.pageIndex(-10), "pageIndex is returning incorrect value for index -10");
        assertEquals(0, helper.pageIndex(0), "pageIndex is returning incorrect value for index 0");
        assertEquals(-1, helper.pageIndex(6), "pageIndex is returning incorrect value for index 6");
    }

    @Test @Order(5) @DisplayName("Empty collection")
    void emptyCollection() {
        PaginationHelper<?> empty = new PaginationHelper<>(List.of(), 10);
        assertEquals( 0, empty.itemCount(), "itemCount is returning incorrect value");
        assertEquals( 0, empty.pageCount(), "pageCount is returning incorrect value");
        assertEquals(-1, empty.pageIndex(0), "pageIndex(0) called when there was an empty collection");
        assertEquals(-1, empty.pageIndex(1), "pageIndex(1) called when there was an empty collection");
        assertEquals(-1, empty.pageIndex(-1), "pageIndex(-1) called when there was an empty collection");
        assertEquals(-1, empty.pageItemCount(0), "pageItemCount is returning incorrect value for page 0");
        assertEquals(-1, empty.pageItemCount(1), "pageItemCount is returning incorrect value for page 1");
    }

    @Test @Order(6) @DisplayName("four item per 4")
    void four() {
        PaginationHelper<?> empty = new PaginationHelper<>(List.of(1,2,3,4), 4);
        assertEquals(-1, empty.pageItemCount(1), "pageItemCount is returning incorrect value for page 1");
    }
}