public class ShapeTest {

    public class MockShape extends Shape {
        @Override
            protected Mesh getMesh(final boolean isStatic, final int verticesNum, final int maxIndices, final VertexAttribute... vAttribs){
                    return Mockito.mock(Mesh.class);
        }
    }

    public void testConstructorMock() {
        Shape s = new MockShape(....)
    }
}