import org.junit.*;
import static org.junit.Assert.*;
import java.util.Arrays;
import org.junit.Rule;

public class ClientTest {

  @Rule
  public DatabaseRule database = new DatabaseRule();

  @Test
  public void all_emptyAtFirst() {
    assertEquals(Client.all().size(), 0);
  }

  @Test
  public void equals_returnsTrueIfNamesAretheSame() {
    Client firstClient = new Client("Gavrilo Princip", 1);
    Client secondClient = new Client("Gavrilo Princip", 1);
    assertTrue(firstClient.equals(secondClient));
  }

  @Test
  public void save_savesIntoDatabase_true() {
    Client myClient = new Client("Gavrilo Princip", 1);
    myClient.save();
    assertTrue(Client.all().get(0).equals(myClient));
  }

  @Test
  public void find_findClientInDatabase_true() {
    Client myClient = new Client("Gavrilo Princip", 1);
    myClient.save();
    Client savedClient = Client.find(myClient.getId());
    assertTrue(myClient.equals(savedClient));
  }

  @Test
  public void update_updatesClientNameInDatabase_newName() {
    Client myClient = new Client("Gavrilo Princip", 1);
    myClient.save();
    myClient.update("The City of Sarajevo", 1);
    assertEquals(myClient.getName(), "The City of Sarajevo", "The City of Sarajevo");
  }

  @Test
  public void delete_deletesClientEntry_true() {
    Client myClient = new Client("Gavrilo Princip", 1);
    myClient.save();
    myClient.delete();
    assertEquals(Client.all().size(), 0);
  }

}

import org.junit.*;
import static org.junit.Assert.*;
import java.util.Arrays;
import org.junit.Rule;

public class ClientTest {

  @Rule
  public DatabaseRule database = new DatabaseRule();

  @Test
  public void all_emptyAtFirst() {
    assertEquals(Client.all().size(), 0);
  }

  @Test
  public void equals_returnsTrueIfNamesAretheSame() {
    Client firstClient = new Client("Gavrilo Princip", 1);
    Client secondClient = new Client("Gavrilo Princip", 1);
    assertTrue(firstClient.equals(secondClient));
  }

  @Test
  public void save_savesIntoDatabase_true() {
    Client myClient = new Client("Gavrilo Princip", 1);
    myClient.save();
    assertTrue(Client.all().get(0).equals(myClient));
  }

  @Test
  public void find_findClientInDatabase_true() {
    Client myClient = new Client("Gavrilo Princip", 1);
    myClient.save();
    Client savedClient = Client.find(myClient.getId());
    assertTrue(myClient.equals(savedClient));
  }

  @Test
  public void update_updatesClientNameInDatabase_newName() {
    Client myClient = new Client("Gavrilo Princip", 1);
    myClient.save();
    myClient.update("The City of Sarajevo", 1);
    assertEquals(myClient.getName(), "The City of Sarajevo", "The City of Sarajevo");
  }

  @Test
  public void delete_deletesClientEntry_true() {
    Client myClient = new Client("Gavrilo Princip", 1);
    myClient.save();
    myClient.delete();
    assertEquals(Client.all().size(), 0);
  }

  @Test
  public void save_savesStylistIdIntoDB_true() {
    Stylist myStylist = new Stylist("Franz Ferdinand");
    myStylist.save();
    Client myClient = new Client("Gavrilo Princip", myStylist.getId());
    myClient.save();
    Client savedClient = Client.find(myClient.getId());
    assertEquals(savedClient.getStylistId(), myStylist.getId());
  }

}

Add test to ensure Stylist number is saved properly in Client database entry.