It can be done using MockedConstruction from Mockito:

@Test
public void barTest() {
    try (MockedConstruction<Bar> barConstructionMock = mockConstruction(Bar.class)) {
        new Foo().foo();

        List<Bar> constructedBars = barConstructionMock.constructed();
        assertEquals(1, constructedBars.size());
        Bar barMock = constructedBars.get(0);
        verify(barMock, times(1)).someMethod();
    }
}