使用 Mockito 模拟静态方法

static unit-testing mocking java mockito

2022-08-31 04:28:40

我写了一个工厂来生产对象：java.sql.Connection

public class MySQLDatabaseConnectionFactory implements DatabaseConnectionFactory {

    @Override public Connection getConnection() {
        try {
            return DriverManager.getConnection(...);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }
}

我想验证传递给的参数，但我不知道如何模拟静态方法。我正在使用JUnit 4和Mockito进行测试用例。有没有一种好方法来模拟/验证这个特定的用例？DriverManager.getConnection

答案 1

在 Mockito 之上使用 PowerMockito。

示例代码：

@RunWith(PowerMockRunner.class)
@PrepareForTest(DriverManager.class)
public class Mocker {

    @Test
    public void shouldVerifyParameters() throws Exception {

        //given
        PowerMockito.mockStatic(DriverManager.class);
        BDDMockito.given(DriverManager.getConnection(...)).willReturn(...);

        //when
        sut.execute(); // System Under Test (sut)

        //then
        PowerMockito.verifyStatic();
        DriverManager.getConnection(...);

    }

更多信息：

为什么 Mockito 不嘲笑静态方法？

答案 2

从 Mockito 3.4.0 开始，就可以在 Mockito 中模拟静态方法。有关更多详细信息，请参阅：

https://github.com/mockito/mockito/releases/tag/v3.4.0

https://github.com/mockito/mockito/issues/1013

https://javadoc.io/doc/org.mockito/mockito-core/latest/org/mockito/Mockito.html#static_mocks

assertEquals("foo", Foo.method());
try (MockedStatic mocked = mockStatic(Foo.class)) {
 mocked.when(Foo::method).thenReturn("bar");
 assertEquals("bar", Foo.method());
 mocked.verify(Foo::method);
}
assertEquals("foo", Foo.method());

在你的例子中，像这样的东西：

  @Test
  public void testStaticMockWithVerification() throws SQLException {
    try (MockedStatic<DriverManager> dummy = Mockito.mockStatic(DriverManager.class)) {
      DatabaseConnectionFactory factory = new MySQLDatabaseConnectionFactory();
      dummy.when(() -> DriverManager.getConnection("arg1", "arg2", "arg3"))
        .thenReturn(new Connection() {/*...*/});

      factory.getConnection();

      dummy.verify(() -> DriverManager.getConnection(eq("arg1"), eq("arg2"), eq("arg3")));
    }
  }

注意：模拟静态方法需要模拟内联依赖项，而不是模拟核心。

对于 JUnit5，还要添加以下内容：

<dependency>
  <groupId>org.mockito</groupId>
  <artifactId>mockito-junit-jupiter</artifactId>
  <version>${mockito.version}</version>
  <scope>test</scope>
</dependency>