After applying your update, it was noticed that the source and target documents for the value of the text font size within the TextBox object have 14, while by calling the getFont().GetSize() method over the mentioned object, the value 10 is obtained.
shape = shapes.get(3);
assertEquals("TextBox", shape.getClass().getSimpleName());
assertEquals(4, shape.getId());
assertEquals("Sélectionnez \nl'unité", shape.getText());
assertEquals("Arial", shape.getFont().getName());
assertEquals(10, shape.getFont().getSize()); // it should be 14, not 10