Exercise: Being Skooled By J.B. In DRY

gistfile2.java

package rules;

public class RulesForNextGeneration {
  private Cell cell;

  public RulesForNextGeneration itTurnsOutThat(Cell cell) {
    this.cell = cell;
    return this;
  }

  public boolean comesAlive() {
    if (cell.isAlive() && cell.numberOfLiveNeighbors == 2) return true;
    return (cell.numberOfLiveNeighbors == 3);
  }
}

gistfile3.java

package rules;

public class Cell {
  protected int numberOfLiveNeighbors;
  private CellState state;

  public Cell() {
    this.state = CellState.DEAD;
  }

  public Cell withLiveNeighbors(int numberOfLiveNeighbors) {
    this.numberOfLiveNeighbors = numberOfLiveNeighbors;
    return this;
  }

  public Cell thatIsAlive() {
    this.state = CellState.ALIVE;
    return this;
  }

  public boolean isAlive() {
    return (state == CellState.ALIVE);
  }

}

gistfile4.java

package rules;

public enum CellState {
  DEAD, ALIVE
}

RulesForNextGenerationTest

package rules;

import static org.junit.Assert.*;

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

public class RulesForNextGenerationTest {
  private RulesForNextGeneration inNextGeneration;

  @Before
  public void setup() {
    inNextGeneration = new RulesForNextGeneration();
  }

  @Test
  public void deadCellWith_0_LiveNeighbors_StaysDead() throws Exception {
    assertIsDeadNextTime(new Cell().withLiveNeighbors(0));
  }

  @Test
  public void deadCellWith_1_LiveNeighbors_StaysDead() throws Exception {
    assertIsDeadNextTime(new Cell().withLiveNeighbors(1));
  }

  @Test
  public void deadCellWith_2_LiveNeighbors_StaysDead() throws Exception {
    assertIsDeadNextTime(new Cell().withLiveNeighbors(2));
  }

  @Test
  public void deadCellWith_3_LiveNeighbors_ComesAlive() throws Exception {
    assertIsAliveNextTime(new Cell().withLiveNeighbors(3));
  }

  @Test
  public void deadCellWith_4_LiveNeighbors_staysdead() throws Exception {
    assertIsDeadNextTime(new Cell().withLiveNeighbors(4));
  }

  @Test
  public void liveCellWith_0_LiveNeighbors_Dies() throws Exception {
    assertIsDeadNextTime(new Cell().thatIsAlive().withLiveNeighbors(0));
  }

  @Test
  public void liveCellWith_1_LiveNeighbors_Dies() throws Exception {
    assertIsDeadNextTime(new Cell().thatIsAlive().withLiveNeighbors(1));
  }

  @Test
  public void liveCellWith_2_LiveNeighbors_StaysAlive() throws Exception {
    assertIsAliveNextTime(new Cell().thatIsAlive().withLiveNeighbors(2));
  }

  @Test
  public void liveCellWith_3_LiveNeighbors_StaysAlive() throws Exception {
    assertIsAliveNextTime(new Cell().thatIsAlive().withLiveNeighbors(3));
  }

  @Test
  public void liveCellWith_4_LiveNeighbors_Dies() throws Exception {
    assertIsDeadNextTime(new Cell().thatIsAlive().withLiveNeighbors(4));
  }

  private void assertIsAliveNextTime(Cell cell) {
    assertTrue(inNextGeneration.itTurnsOutThat(cell).comesAlive());
  }

  private void assertIsDeadNextTime(Cell cell) {
    assertFalse(inNextGeneration.itTurnsOutThat(cell).comesAlive());
  }

  // Test list

  // TODO a dead cell with 0 live neighbors stays dead.
  // TODO a dead cell with 1 live neighbors stays dead.
  // TODO a dead cell with 2 live neighbors stays dead.
  // TODO a dead cell with 3 live neighbors comes alive.
  // TODO a dead cell with 4 live neighbors stays dead.

  // TODO a live cell with 0 live neighbors dies.
  // TODO a live cell with 1 live neighbor dies.
  // TODO a live cell with 2 live neighbors stays alive.
  // TODO a live cell with 3 live neighbors stays alive.
  // TODO a live cell with 4 live neighbors dies.

}