### Question:
GraphViz implements Renderer { @Override public void writeDirected (DirectedGraph graph, PrintWriter writer) { mWriter = writer; writeDotFile (graph); } GraphViz();  GraphViz(String path);  GraphViz(String path, String defaultType); void setDebugMode(boolean value); boolean inDebugMode(); @Override void setDefaultFileType(String fileType); @Override String getDefaultFileType(); @Override void write(String filename, DirectedGraph graph); @Override void write(String filename, String fileType, DirectedGraph graph); @Override void writeDirected(DirectedGraph graph, PrintWriter writer); @Override void writeDirected(DirectedGraph graph, String filename); @Override void writeDirected(DirectedGraph graph, String filename, String fileType);  }### Answer:
@Test public void testWriteSimpleGraphWithOnlyDefaultValues () { DirectedGraph graph = generateSimpleGraphWithOnlyDefaultValues (); StringWriter writer = new StringWriter (); new GraphViz ("").writeDirected (graph, new PrintWriter (writer)); assertEquals (DOT_FILE_FOR_SIMPLE_GRAPH_WITH_ONLY_DEFAULT_VALUES, writer.toString ()); }
@Test public void testWriteSimpleGraphWithNoDefaultValues () { DirectedGraph graph = generateSimpleGraphWithNoDefaultValues (); StringWriter writer = new StringWriter (); new GraphViz ("").writeDirected (graph, new PrintWriter (writer)); assertEquals (DOT_FILE_FOR_SIMPLE_GRAPH_WITH_NO_DEFAULT_VALUES, writer.toString ()); }