### Question:
HTMLFlow extends Canvas { @Override @VaadinIntegration public void paintContent(PaintTarget target) throws PaintException { super.paintContent(target); if (contentsResource != null) { target.addAttribute("*contentsResource", contentsResource); } } HTMLFlow();  HTMLFlow(String contents); void setAllowCaching(Boolean allowCaching); Boolean getAllowCaching(); void setCaptureSCComponents(Boolean captureSCComponents); Boolean getCaptureSCComponents(); void setContents(String contents); String getContents(); void setContentsURL(String contentsURL); String getContentsURL(); @VaadinIntegration void setContentsResource(Resource contentsResource); @VaadinIntegration Resource getContentsResource(); void setDynamicContents(Boolean dynamicContents); Boolean getDynamicContents(); void setEvalScriptBlocks(Boolean evalScriptBlocks); Boolean getEvalScriptBlocks(); void setHttpMethod(SendMethod httpMethod); SendMethod getHttpMethod(); void setLoadingMessage(String loadingMessage); String getLoadingMessage(); void setContentsType(ContentsType contentsType); ContentsType getContentsType(); void setContentsURLParams(@SuppressWarnings("rawtypes") Map contentsURLParams); @Override @VaadinIntegration void paintContent(PaintTarget target);  }### Answer:
@Test public void test_ignoresContentsResourceAttributeWhenUnset() throws PaintException { final JsonPaintTarget target = mock(JsonPaintTarget.class); htmlFlow.paintContent(target); verify(target, never()).addAttribute(eq("*contentsResource"), any(Resource.class)); }