• 4 PowerMock
  • 4.1 Maven dependencies
  • 4.2 寫 Java code

1<properties>
2	<powermock.version>2.0.9</powermock.version>
3</properties>
4
5<dependencyManagement>
6	<dependencies>
7		<dependency>
8			<groupId>org.springframework.boot</groupId>
9			<artifactId>spring-boot-dependencies</artifactId>
10			<version>2.7.1</version>
11			<type>pom</type>
12			<scope>import</scope>
13		</dependency>
14	</dependencies>
15</dependencyManagement>
16
17<dependencies>
18	<dependency>
19		<groupId>org.springframework.boot</groupId>
20		<artifactId>spring-boot-starter-web</artifactId>
21	</dependency>
22
23	<dependency>
24		<groupId>org.apache.commons</groupId>
25		<artifactId>commons-lang3</artifactId>
26	</dependency>
27
28	<dependency>
29		<groupId>org.springframework.boot</groupId>
30		<artifactId>spring-boot-starter-test</artifactId>
31		<scope>test</scope>
32	</dependency>
33
34	<dependency>
35		<groupId>org.junit.vintage</groupId>
36		<artifactId>junit-vintage-engine</artifactId>
37		<scope>test</scope>
38	</dependency>
39
40	<dependency>
41		<groupId>org.powermock</groupId>
42		<artifactId>powermock-module-junit4</artifactId>
43		<version>${powermock.version}</version>
44		<scope>test</scope>
45	</dependency>
46
47	<dependency>
48		<groupId>org.powermock</groupId>
49		<artifactId>powermock-api-mockito2</artifactId>
50		<version>${powermock.version}</version>
51		<scope>test</scope>
52	</dependency>
53
54	<dependency>
55		<groupId>org.powermock</groupId>
56		<artifactId>powermock-module-junit4-rule-agent</artifactId>
57		<version>${powermock.version}</version>
58		<scope>test</scope>
59	</dependency>
60
61	<dependency>
62		<groupId>org.mockito</groupId>
63		<artifactId>mockito-core</artifactId>
64		<version>3.12.4</version> <!--$NO-MVN-MAN-VER$-->
65		<scope>test</scope>
66	</dependency>
67</dependencies>
68
69<build>
70	<plugins>
71		<plugin>
72			<groupId>org.springframework.boot</groupId>
73			<artifactId>spring-boot-maven-plugin</artifactId>
74			<executions>
75				<execution>
76					<goals>
77						<goal>repackage</goal>
78					</goals>
79				</execution>
80			</executions>
81		</plugin>
82
83		<plugin>
84			<groupId>org.apache.maven.plugins</groupId>
85			<artifactId>maven-surefire-plugin</artifactId>
86			<version>3.0.0-M7</version>
87			<configuration>
88				<argLine>-Djdk.attach.allowAttachSelf=true</argLine>
89			</configuration>
90		</plugin>
91	</plugins>
92</build>

• JDK-8180425 : Release Note: Attach API cannot be used to attach to the current VM by default

@Component
public class MyComponent {

}

1@PrepareForTest({ StringUtils.class, RandomStringUtils.class })
2@PowerMockIgnore({ "com.sun.org.apache.xerces.*", "javax.xml.*", "org.xml.*", "javax.management.*" })
3@SpringBootTest
4@RunWith(SpringRunner.class)
5public class MockStaticSpringTest {
6
7    @Autowired
8    MyComponent myComponent;
9
10    @Rule
11    public PowerMockRule powerMockRule = new PowerMockRule();
12
13    @Before
14    public void setUp() {
15        PowerMockito.spy(StringUtils.class);
16        PowerMockito.mockStatic(RandomStringUtils.class);
17    }
18
19    // Spring Boot test，可以測試 Spring context 能唔能夠成功 load 到
20    @Test
21    public void contextLoads() {
22        assertNotNull(myComponent);
23    }
24
25    @Test
26    public void test_mockStatic_StringUtils() {
27        assertTrue(StringUtils.isBlank("   "));
28        PowerMockito.when(StringUtils.isBlank(any())).thenReturn(false);
29        assertFalse(StringUtils.isBlank("   "));
30    }
31
32    @Test
33    public void test_mockStatic_RandomStringUtils() {
34        assertNull(RandomStringUtils.randomAlphabetic(10));
35        PowerMockito.when(RandomStringUtils.randomAlphabetic(anyInt())).thenReturn("Hello World!");
36        assertEquals("Hello World!", RandomStringUtils.randomAlphabetic(10));
37    }
38}

• 我地用既係 SpringRunner 而唔係 PowerMockRunner。
  • 正因為咁，所以我地要加 @Rule public PowerMockRule powerMockRule = new PowerMockRule();
    • 呢個 property 一定要係 public。
    • 呢個 property 要先 initialize，例如 new PowerMockRule()。
• @PowerMockIgnore 有可能需要用到。
• 我地要 mock static 既 class 係 Apache Commons Lang3 既 StringUtils 以及 RandomStringUtils。
• PowerMock 使用上其實同 Mockito 係非常相似。
  • PowerMockito.mockStatic(class) 默認會令 mock object 既所有 methods 都冇任何 implementation，即係如果有 return type，佢就會返回 null 或者 false 之類既默認 value，除非我地用 when-then 既寫法賦予被測試既 method 一啲新既 behavior。
  • PowerMockito.spy(class) 係當我地需要 mock object 默認用返本身既 implementation，除非我地用 when-then 既寫法賦予被測試既 method 一啲新既 behavior。