How to write a Test for methods working with HashMaps

Question

I'm trying to write a test methode like:

import junitparams.JUnitParamsRunner;
import junitparams.Parameters;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;

import java.util.Arrays;

import static org.junit.Assert.assertEquals;

@RunWith(JUnitParamsRunner.class)
public class TestBinaryIntArraySearchImpl {

    private IntArraySearcher binaryIntArraySearch;

    @Before
    public void before(){

        binaryIntArraySearch = new BinaryIntArraySearchImpl();
    }

    @After
    public void after(){
        binaryIntArraySearch = null;
    }
    @Test
    @Parameters({
            "1                  ,   1                   ,true",
            "3-4                ,   8                   ,false",
            "1-3                ,   7                   ,false",
            "1-2-3-4-5-6-7-8    ,   9                   ,false",
            "3-6-7-7-8-9        ,   7                   ,true",
            "7-7-7-7-7          ,   7                   ,true"
    })
    public void testSearch(String unSorted, int numbersToSearch, boolean found) {
        int[] unSortedArray =
                Arrays.stream(unSorted.split("-"))
                        .map(Integer::valueOf)
                        .mapToInt(Integer::intValue)
                        .toArray();
        assertEquals(
                found,
                binaryIntArraySearch.search(unSortedArray, numbersToSearch)
        );
    }
    @Test
    public void testSearch_emptyList() {
        int[] emptyList = {};
        assertEquals(
                false,
                binaryIntArraySearch.search(emptyList, 3)
        );
    }

for a methode working with a hashmap. But because my knowledge about writing tests isn't that good and my research didn't realy pay of I thought i make a question and maybe one of u guys can help me with my problem.

For example here're two of the methods i want to test:

Map<String, Integer> marketplaceMaterialStock = new HashMap<>();

 public boolean checkMaterialStock(String materialOne, int amountOne, String materialTwo, int amountTwo){
        if(this.marketplaceMaterialStock.get(materialOne)>=amountOne && this.marketplaceMaterialStock.get(materialTwo) >= amountTwo){
            return true;
        }
        return false;
    }

    public boolean buyMaterial(String materialOne, int amountOne , String materialTwo , int amountTwo){
        int newStockOne;
        int newStockTwo;
        if(this.marketplaceMaterialStock.get(materialOne)>=amountOne && this.marketplaceMaterialStock.get(materialTwo) >= amountTwo){
            newStockOne = this.marketplaceMaterialStock.get(materialOne) - amountOne;
            newStockTwo = this.marketplaceMaterialStock.get(materialTwo) - amountTwo;
            this.marketplaceMaterialStock.replace(materialOne, this.marketplaceMaterialStock.get(materialOne) , newStockOne);
            this.marketplaceMaterialStock.replace(materialTwo, this.marketplaceMaterialStock.get(materialTwo) , newStockTwo);

            return true;
        }
        return false;
    }

maybe somebody can help me out or can give me an address where something like this is explained.