How to use AtLeastXNumberOfInvocationsCheckerTest class of org.mockito.internal.verification.checkers package

Since you are loading configuration class MyApplication.class datasource bean will be created, Try moving datasource in another bean which is not used in a test, make sure all classes loaded for tests are not dependant on datasource.
Or
In your tests create a config class marked with @TestConfiguration and include it in SpringBootTest(classes=TestConfig.class) mocking data source there like

@Bean
public DataSource dataSource() {
    return Mockito.mock(DataSource.class);
}

But this may fail since method call to this mocked datasouce for connection will return null, In that case, you'll have to create an in-memory datasource and then mock jdbcTemplate and rest of dependencies.

You can use PowerMockito

See the example:

Second second = Mockito.mock(Second.class);
whenNew(Second.class).withNoArguments().thenReturn(second);

But re-factoring is better decision.

You are correct that is not a design issue on your part. Without PowerMock, your options become a bit murkier, though.

I would suggest creating a non-static wrapper for the FrameworkUtil class that you can inject and mock.

Update: (David Wallace)

So you add a new class to your application, something like this

public class UtilWrapper {
    public Bundle getBundle(Class<?> theClass) {
        return FrameworkUtil.getBundle(theClass);
    }
}

This class is so simple that you don't need to unit test it. As a general principle, you should only EVER write unit tests for methods that have some kind of logic to them - branching, looping or exception handling. One-liners should NOT be unit tested.

Now, within your application code, add a field of type UtilWrapper, and a setter for it, to every class that currently calls FrameworkUtil.getBundle. Add this line to the construtor of each such class

utilWrapper = new UtilWrapper();

And replace every call to FrameworkUtil.getBundle with utilWrapper.getBundle.

Now in your test, you make a mock UtilWrapper and stub it to return whatever Bundle you like.

when(mockUtilWrapper.getBundle(ConfigService.class)).thenReturn(someBundleYouMade);

and for the class that you're testing, call setUtilWrapper(mockUtilWrapper) or whatever. You don't need this last step if you're using @InjectMocks.

Now your test should all hang together, but using your mocked UtilWrapper instead of the one that relies on FrameworkUtil.

You need to do this.

when(userRepository.save(Mockito.any(User.class)))
                .thenAnswer(i -> i.getArguments()[0]);

And now you can obtain user which you pass as argument.

Here's what I've been doing to cope with the situation.

I use global imports on a new test class.

import static org.junit.Assert.*;
import static org.mockito.Mockito.*;
import static org.mockito.Matchers.*;

When you are finished writing your test and need to commit, you just CTRL+SHIFT+O to organize the packages. For example, you may just be left with:

import static org.mockito.Mockito.doThrow;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;
import static org.mockito.Matchers.anyString;

This allows you to code away without getting 'stuck' trying to find the correct package to import.

You can change the System.in stream using System.setIn() method.

Try this,

@Test
public void shouldTakeUserInput() {
    InputOutput inputOutput= new InputOutput();

    String input = "add 5";
    InputStream in = new ByteArrayInputStream(input.getBytes());
    System.setIn(in);

    assertEquals("add 5", inputOutput.getInput());
}

You have just modified the System.in field. System.in is basically an InputStream which reads from the console (hence your input in the console). But you just modified it and let the system to read from the provided inputstream instead. So it wont read from console anymore but from the inputstream provided.

Using void reset(T... mocks) will reset all stubbings on the mocks. If you just need to reset the invocation counts for subsequent verifications, use void clearInvocations(T... mocks).

You could use atLeast(0) in combination with ArgumentCaptor:

ArgumentCaptor<String> propertyKeyCaptor = ArgumentCaptor.forClass(String.class);
Mockito.verify(foo, atLeast(0)).getProperty(propertyKeyCaptor.capture(), anyString());

ArgumentCaptor<String> propertyKeyCaptor2 = ArgumentCaptor.forClass(String.class);
Mockito.verify(foo, atLeast(0)).getProperty(propertyKeyCaptor2.capture());

List<String> propertyKeyValues = propertyKeyCaptor.getAllValues();
List<String> propertyKeyValues2 = propertyKeyCaptor2.getAllValues();

assertTrue(!propertyKeyValues.isEmpty() || !propertyKeyValues2.isEmpty()); //JUnit assert -- modify for whatever testing framework you're using

Spring's MockHttpServletRequest and MockHttpServletResponse are useful for that purpose. E.g.

    MockHttpServletRequest request = new MockHttpServletRequest();
    MockHttpServletResponse response = new MockHttpServletResponse();
    request.addHeader(HttpHeaders.HOST, "myhost.com");
    request.setLocalPort(PORT_VALID); // e.g. 8081
    request.setRemoteAddr(REQUEST_IP); // e.g. 127.0.0.1

then I can call myclass.method(request, response, ...) and check whether some attribute has been correctly set into the request, e.g.

    MyBean attr = (MyBean) request.getAttribute(ATTRIBUTE_NAME));
    // do my Assert.* stuff with 'attr'

MockHttpServletRequest and MockHttpServletResponse work fine where mock(HttpServletRequest.class) fails, for instance where you need to get back the real content of a request attribute which has been previously set within your business logic.