所谓 given 即构造参数和条件（如mock 依赖的bean ），所谓 when 执行目标方法； 所谓 then 即在给定的参数和条件下，执行目标方法后，我们的预期是什么。
下面是示例代码：
@Test
public void shouldDeliverCargoToDestination() {
// given
Driver driver = new Driver("Teddy");
Cargo cargo = new Cargo();
Position destinationPosition = new Position("52.229676", "21.012228");
Truck truck = new Truck();
truck.setDriver(driver);
truck.load(cargo);
truck.setDestination(destinationPosition);
// when
truck.driveToDestination();
// then
assertEquals(destinationPosition, truck.getCurrentPosition());
}
import java.util.Iterator;
import java.util.List;
public class SomeUtils {
/**
* 使用英文逗号拼接字符串
*/
public static String joinWithDot(List<String> params){
StringBuilder stringBuilder = new StringBuilder();
Iterator<String> iterator = params.iterator();
while (iterator.hasNext()) {
stringBuilder.append(iterator.next()).append(".");
}
return stringBuilder.toString();
}
}
实际编码对字符串进行拼接时建议使用 StringJoiner 类
我们使用
介绍的 Squaretest 插件自动生成单测：
import org.junit.Test;
import java.util.Arrays;
import static org.junit.Assert.assertEquals;
public class SomeUtilsTest {
@Test
public void testJoinWithDot() {
assertEquals("result", SomeUtils.joinWithDot(Arrays.asList("value")));
}
}
我们在此基础上进行修改：
public class SomeUtilsTest {
@Test
public void testJoinWithDot() {
assertEquals(null, SomeUtils.joinWithDot(null));
assertEquals("a.b", SomeUtils.joinWithDot(Arrays.asList("a","b")));
assertEquals("a.null.c", SomeUtils.joinWithDot(Arrays.asList("a",null,"c")));
}
}
虽然，这里看似只有断言，比如：
assertEquals(null, SomeUtils.joinWithDot(null));
这里其实是一种简写，实际上依然符合 Given when then 的模式：
@Test
public void testJoinWithDot() {
// given
List<String> params = null;
// when
String result = SomeUtils.joinWithDot(null);
// then
assertEquals(null, result);
}
运行单元测试，发现出现空指针：
单元测试经典三问：是什么，为什么，怎么做？一、背景二、经典三问三、总结
说明我们代码不够健壮，需要修改：
/**
* 使用英文逗号拼接字符串
*/
public static String joinWithDot(List<String> params){
if(CollectionUtils.isEmpty(params)){
return null;
}
StringBuilder stringBuilder = new StringBuilder();
Iterator<String> iterator = params.iterator();
while (iterator.hasNext()) {
stringBuilder.append(iterator.next()).append(".");
}
return stringBuilder.toString();
}
@Service
public class UserManager {
@Setter
private UserDAO userDAO;
public UserDAO getUserDAO() {
return userDAO;
}
public void setUserDAO(UserDAO userDAO) {
this.userDAO = userDAO;
}
public List<UserDO> someThing(Param param) {
List<UserDO> result = new ArrayList<>();
if(param == null) {
return result;
}
List<String> userIds = param.getUserIds();
if(CollectionUtils.isEmpty(userIds)) {
return result;
}
List<UserDO> users = userDAO.findByIds(userIds);
if(CollectionUtils.isEmpty(users)) {
return result;
}
return users.stream().filter(UserDO::getCanShow).collect(Collectors.toList());
}
}
注：通常依赖的 Bean 的方法时，
继续使用插件一键生成单元测试代码：
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.junit.MockitoJUnitRunner;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import static org.junit.Assert.assertEquals;
import static org.mockito.Mockito.when;
@RunWith(MockitoJUnitRunner.class)
public class UserManagerTest {
@Mock
private UserDAO mockUserDAO;
@InjectMocks
private UserManager userManagerUnderTest;
@Test
public void testSomeThing() {
// Setup
final Param param = new Param();
param.setUserIds(Arrays.asList("value"));
param.setOthers("others");
// Configure UserDAO.findByIds(...).
final UserDO userDO = new UserDO();
userDO.setCanShow(false);
userDO.setName("name");
final List<UserDO> userDOS = Arrays.asList(userDO);
when(mockUserDAO.findByIds(Arrays.asList("value"))).thenReturn(userDOS);
// Run the test
final List<UserDO> result = userManagerUnderTest.someThing(param);
// Verify the results
}
@Test
public void testSomeThing_UserDAOReturnsNoItems() {
// Setup
final Param param = new Param();
param.setUserIds(Arrays.asList("value"));
param.setOthers("others");
when(mockUserDAO.findByIds(Arrays.asList("value"))).thenReturn(Collections.emptyList());
// Run the test
final List<UserDO> result = userManagerUnderTest.someThing(param);
// Verify the results
assertEquals(Collections.emptyList(), result);
}
}
我们根据业务逻辑，对生成的单测代码进行简单修改即可：
@Test
public void testSomeThing() {
// given
final Param param = new Param();
List<String> userIds = Arrays.asList("value");
param.setUserIds(userIds);
param.setOthers("others");
final UserDO userCanNotShow = new UserDO();
userCanNotShow.setCanShow(false);
userCanNotShow.setName("name");
final UserDO userCanShow = new UserDO();
userCanShow.setCanShow(true);
userCanShow.setName("name");
final List<UserDO> userDOS = Arrays.asList(userCanNotShow, userCanShow);
when(mockUserDAO.findByIds(userIds)).thenReturn(userDOS);
// when
final List<UserDO> result = userManagerUnderTest.someThing(param);
// then
assertEquals(1, result.size());
assertSame(userCanShow, result.get(0));
}
