TDD a Java Set - Attempt 4

Set.java

package set;

import java.util.Objects;

public class Set {
    private String[] elements = new String[0];
    private int next;

    public boolean isEmpty() {
        return next == 0;
    }

    public int size() {
        return next;
    }

    public boolean add(String value) {
        String[] newElements = extendArray(elements);
        newElements[this.next] = value;
        next++;
        elements = newElements;
        return true;
    }

    private String[] extendArray(String[] elements) {
        String [] newElements = new String[ next + 1];
        copyArray(elements, newElements);
        return newElements;
    }

    private void copyArray(String[] elements, String[] newElements) {
        for (int i = 0; i < elements.length; i++) {
            newElements[i] = elements[i];
        }
    }

    public boolean remove(String value) {
        for (int i = 0; i < next; i++) {
            if(Objects.equals(elements[i], value)){
                elements[i] = value;
                elements[next - 1] = null;
                next--;
            }
        }

        return true;
    }
}

SetTest.java

package set;

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

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


public class SetTest {

    private Set set;

    @BeforeEach
    void setUp() {
        set = new Set();
    }

    @Test
    void is_empty() {
        assertTrue(set.isEmpty());
    }

    @Test
    void empty_set_has_no_size() {
        assertEquals(0, set.size());
    }

    @Test
    void adds_one_element() {
        set.add("one");

        assertFalse(set.isEmpty());
        assertEquals(1, set.size());
    }

    /*
       this test sucks because it's not specific enough.  There's a possibility where
       if you did logic wrong, you could add nulls to the set and this still passes. We're
       not checking that those specific values are in the set, so you could end up with a false positive here.

       Next time around, lets try asserting on contains() here, but then that means I'd be implementing 2 functions at once (add and contains)
       which feels like way too big of a step for TDD.
    */
    @Test
    void adds_multiple_elements() {
        set.add("one");
        set.add("two");
        set.add("three");

        assertFalse(set.isEmpty());
        assertEquals(3, set.size());
    }

    @Test
    void remove() {
        set.add("one");
        set.add("two");
        set.add("three");
        set.remove("two");

        assertFalse(set.isEmpty());
        assertEquals(2, set.size());
    }
}