TestNG + Mockito + PowerMock

pom.xml

        <dependency>
            <groupId>org.testng</groupId>
            <artifactId>testng</artifactId>
            <version>7.1.0</version>
        </dependency>
        <dependency>
            <groupId>org.mockito</groupId>
            <artifactId>mockito-core</artifactId>
            <version>3.3.3</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.powermock</groupId>
            <artifactId>powermock-api-mockito2</artifactId>
            <version>2.0.7</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.powermock</groupId>
            <artifactId>powermock-module-testng</artifactId>
            <version>2.0.7</version>
            <scope>test</scope>
        </dependency>

SomeTest.java

import org.powermock.core.classloader.annotations.PrepareForTest
import org.powermock.modules.testng.PowerMockObjectFactory
import org.testng.IObjectFactory
import org.testng.annotations.ObjectFactory
import org.testng.annotations.Test
import static org.mockito.Mockito.*
import static org.powermock.api.mockito.PowerMockito.mockStatic

@PrepareForTest(AStaticClass.class)
public class SomeTest {
  
    @ObjectFactory
    IObjectFactory getObjectFactory() {
        return new PowerMockObjectFactory()
    }
  
  @Test
  public void myTestMethod {

        mockStatic(AStaticClass)
        when(AStaticClass.myMethod()).thenReturn(stuff)

        // then use
        assertThat(AStaticClass.myMethod(), is(stuff))
}