BoardTest.java

import org.junit.Before;
import org.junit.Test;

import java.util.Arrays;
import java.util.ArrayList;

import static junit.framework.Assert.assertTrue;
import static org.hamcrest.CoreMatchers.not;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertThat;

public class BoardTest {
    private Board board;

    @Before
    public void setUp() {
      board = new Board();
    }

    @Test
    public void testInitializesCells() {
      assertEquals("2", board.getCells()[1]);
    }

    @Test
    public void testIsAvailableReturnsTrueWhenAvailable() {
        for(int i = 0; i <= 7; i++) {
            board.getCells()[i] = "X";
        }
        assertTrue(board.hasAvailableCell());
    }

    @Test
    public void testGetRandomCellDoesNotReturnUnavailableCell() {
        String cellID = board.getRandomCell();
        board.getCells()[0] = "X";
        assertThat(cellID, not("1"));
    }

    @Test
    public void testGetRandomCellReturnsTheOnlyOpenCell() {
        board.getCells()[0] = "X";
        board.getCells()[1] = "O";
        board.getCells()[2] = "X";
        board.getCells()[3] = "X";
        board.getCells()[4] = "O";
        board.getCells()[5] = "X";
        board.getCells()[6] = "O";
        board.getCells()[7] = "O";
        String cellID = board.getRandomCell();
        assertEquals("9", cellID);
    }
  ...
}