UUID.randomUUID()
有什么问题 - 它不能被嘲笑
有可能嘲笑吗?或者我的来源有错误?
看一下例子:
1)被测试的类
package com.grayen;
import java.util.UUID;
public class TestedClass {
public UUID getUuid() {
return UUID.randomUUID();
}
public UUID getUuidFromWrapper() {
return UuidWrapper.randomUUID();
}
}
一种方法使用UUID的包装器,我可以模拟该包装器!
2)真正UUID的包装(所有修饰符相同)
package com.grayen;
import java.util.UUID;
public final class UuidWrapper {
public static UUID randomUUID() {
return UUID.randomUUID();
}
}
3)测试(最后一个评论行引发异常)
package com.grayen;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;
import java.util.UUID;
import static org.junit.Assert.assertEquals;
@PrepareForTest({UUID.class, UuidWrapper.class})
@RunWith(PowerMockRunner.class)
public class TestedClassTest {
@Test
public void testMethod() {
UUID uuid = UUID.randomUUID();
PowerMockito.mockStatic(UUID.class);
PowerMockito.mockStatic(UuidWrapper.class);
PowerMockito.when(UUID.randomUUID()).thenReturn(uuid);
PowerMockito.when(UuidWrapper.randomUUID()).thenReturn(uuid);
TestedClass testedClass = new TestedClass();
assertEquals(uuid, testedClass.getUuidFromWrapper());
//assertEquals(uuid, testedClass.getUuid());
}
}
模拟静态方法总是一种脆弱的方法。如果可能,请使用非静态UUID源,然后可以轻松模拟。
例如:
/**
* A source of new {@link UUID} instances.
*/
public interface UuidSource {
/**
* Returns a new {@link UuidSource} that generates UUIDs using {@link UUID#randomUUID}.
*/
public static UuidSource random() {
return UUID::randomUUID;
}
/**
* Returns a new {@link UUID} instance.
*
* <p>The returned value is guaranteed to be unique.
*/
UUID newUuid();
}
然后你可以将它注入TestedClass
,或让TestedClass
有一个私人成员:
public class TestedClass {
private UuidSource uuidSource = UuidSource.random();
public UUID getUUID() {
return uuidSource.newUuid();
}
// etc.
}
然后要测试它,你可以有一个只测试的构造函数,允许注入一个模拟的UuidSource
,或者你可以直接替换uuidSource
字段的值(通过扩大其可见性或使用反射或其他东西)。
作为奖励:这将您的实际生产代码与UUID.randomUUID()
分离。如果以后您决定需要使用版本2 UUID(基于日期时间)或其他版本而不是随机UUID,您也可以轻松地在生产代码中更改它。当人们说使代码更易于测试时,这就是人们的意思,这通常会带来更好的整体设计。
所以我拿了你的代码并开始工作。您需要做的就是将TestedClass.class
添加到您的@PrepareForTest
。
package com.grayen;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;
import java.util.UUID;
import static org.junit.Assert.assertEquals;
@PrepareForTest({
UUID.class,
UuidWrapper.class,
TestedClass.class
})
@RunWith(PowerMockRunner.class)
public class TestedClassTest {
@Test
public void testMethod() {
UUID uuid = UUID.randomUUID();
PowerMockito.mockStatic(UUID.class);
PowerMockito.mockStatic(UuidWrapper.class);
PowerMockito.when(UUID.randomUUID()).thenReturn(uuid);
PowerMockito.when(UuidWrapper.randomUUID()).thenReturn(uuid);
TestedClass testedClass = new TestedClass();
assertEquals(uuid, testedClass.getUuidFromWrapper());
assertEquals(uuid, testedClass.getUuid());
}
}
编辑
我没有看到评论,但是k5_指出了这一点。