How to fix java.lang.IllegalStateException: Failed to load ApplicationContext error?

Question

Java

Hello!
I started to study spring and there was a problem with running the test.
There were many questions on this topic on the Internet, but no matter what I change, nothing helps from the suggestions.

UserSeviceTest class:

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserSeviceTest {
    @Autowired
    private UserSevice userSevice;

    @MockBean
    private UserRepo userRepo;

    @MockBean
    private MailSender mailSender;

    @MockBean
    private PasswordEncoder passwordEncoder;

    @Test
    public void addUser() {
        User user = new User();

        user.setEmail("[email protected]");

        boolean isUserCreated = userSevice.addUser(user);

        Assert.assertTrue(isUserCreated);
        Assert.assertNotNull(user.getActivationCode());
        Assert.assertTrue(CoreMatchers.is(user.getRoles()).matches(Collections.singleton(Role.USER)));

        Mockito.verify(userRepo, Mockito.times(1)).save(user);
        Mockito.verify(mailSender, Mockito.times(1))
                .send(
                        ArgumentMatchers.eq(user.getEmail()),
                        ArgumentMatchers.anyString(),
                        ArgumentMatchers.anyString()
                );
    }

    @Test
    public void addUserFailTest() {
        User user = new User();

        user.setUsername("John");

        Mockito.doReturn(new User())
                .when(userRepo)
                .findByUsername("John");

        boolean isUserCreated = userSevice.addUser(user);

        Assert.assertFalse(isUserCreated);

        Mockito.verify(userRepo, Mockito.times(0)).save(ArgumentMatchers.any(User.class));
        Mockito.verify(mailSender, Mockito.times(0))
                .send(
                        ArgumentMatchers.anyString(),
                        ArgumentMatchers.anyString(),
                        ArgumentMatchers.anyString()
                );
    }

    @Test
    public void activateUser() {
        User user = new User();

        user.setActivationCode("bingo!");

        Mockito.doReturn(user)
                .when(userRepo)
                .findByActivationCode("activate");

        boolean isUserActivated = userSevice.activateUser("activate");

        Assert.assertTrue(isUserActivated);
        Assert.assertNull(user.getActivationCode());

        Mockito.verify(userRepo, Mockito.times(1)).save(user);
    }

    @Test
    public void activateUserFailTest() {
        boolean isUserActivated = userSevice.activateUser("activate me");

        Assert.assertFalse(isUserActivated);

        Mockito.verify(userRepo, Mockito.times(0)).save(ArgumentMatchers.any(User.class));
    }
}

IllegalStateException class:

/*
 * Copyright (c) 1996, 2019, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.lang;

/**
 * Signals that a method has been invoked at an illegal or
 * inappropriate time.  In other words, the Java environment or
 * Java application is not in an appropriate state for the requested
 * operation.
 *
 * @author  Jonni Kanerva
 * @since   1.1
 */
public class IllegalStateException extends RuntimeException {
    /**
     * Constructs an IllegalStateException with no detail message.
     * A detail message is a String that describes this particular exception.
     */
    public IllegalStateException() {
        super();
    }

    /**
     * Constructs an IllegalStateException with the specified detail
     * message.  A detail message is a String that describes this particular
     * exception.
     *
     * @param s the String that contains a detailed message
     */
    public IllegalStateException(String s) {
        super(s);
    }

    /**
     * Constructs a new exception with the specified detail message and
     * cause.
     *
     * <p>Note that the detail message associated with {@code cause} is
     * <i>not</i> automatically incorporated in this exception's detail
     * message.
     *
     * @param  message the detail message (which is saved for later retrieval
     *         by the {@link Throwable#getMessage()} method).
     * @param  cause the cause (which is saved for later retrieval by the
     *         {@link Throwable#getCause()} method).  (A {@code null} value
     *         is permitted, and indicates that the cause is nonexistent or
     *         unknown.)
     * @since 1.5
     */
    public IllegalStateException(String message, Throwable cause) {
        super(message, cause);
    }

    /**
     * Constructs a new exception with the specified cause and a detail
     * message of {@code (cause==null ? null : cause.toString())} (which
     * typically contains the class and detail message of {@code cause}).
     * This constructor is useful for exceptions that are little more than
     * wrappers for other throwables (for example, {@link
     * java.security.PrivilegedActionException}).
     *
     * @param  cause the cause (which is saved for later retrieval by the
     *         {@link Throwable#getCause()} method).  (A {@code null} value is
     *         permitted, and indicates that the cause is nonexistent or
     *         unknown.)
     * @since  1.5
     */
    public IllegalStateException(Throwable cause) {
        super(cause);
    }

    @java.io.Serial
    static final long serialVersionUID = -1848914673093119416L;
}

The error itself:

java.lang.IllegalStateException: Failed to load ApplicationContext

  at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:125)
  at org.springframework.test.context.support.DefaultTestContext.getApplicationContext(DefaultTestContext.java:107)
  at org.springframework.test.context.web.ServletTestExecutionListener.setUpRequestContextIfNecessary(ServletTestExecutionListener.java:190)
  at org.springframework.test.context.web.ServletTestExecutionListener.prepareTestInstance(ServletTestExecutionListener.java:132)
  at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:242)
  at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:227)
  at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:289)
  at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
  at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:291)
  at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:246)
  at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
  at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
  at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
  at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
  at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
  at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
  at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
  at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
  at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
  at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
  at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
  at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
  at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
  at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
  at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
Caused by: java.lang.IllegalStateException: Cannot load configuration class: com.example.sweater.Application

Answer 1

the listing of the IllegalStateException class is definitely superfluous
here, but the stacktrace needs to be looked at more carefully
, it seems that it lacks a configuration here. How does Spring know what UserRepo, UserService, etc. are?
for study: https://www.baeldung.com/spring-boot-testing