Add spec for Graph#to_dot implementation

lib/mosaik/graph/edge.rb

@@ -12,10 +12,6 @@ def initialize(attributes = {})
         @attributes = attributes
       end
 
-      def to_dot
-        attributes.map { |k, v| "#{k}=#{v}" }.join(", ")
-      end
-
       def inspect
         "#<#{self.class.name} attributes=#{attributes.map { |k, v| "#{k}: #{v}" }.join(',')}>"
       end

lib/mosaik/graph/graph.rb

@@ -71,7 +71,16 @@ def tsort_each_child(vertex, &)
       def to_dot
         <<~DOT
           digraph {
-            #{vertices.values.map(&:to_dot).join("\n  ")}
+            #{
+              vertices
+                .values
+                .flat_map do |vertex|
+                vertex
+                  .edges
+                  .filter_map { |k, e| "\"#{vertex.id}\" -#{directed? ? '>' : '-'} \"#{k}\" [#{e.attributes.map { |ek, ev| "#{ek}=#{ev}" }.join(',')}]" }
+              end
+                .join("\n  ")
+            }
           }
         DOT
       end

lib/mosaik/graph/vertex.rb

@@ -22,14 +22,6 @@ def remove_edge(id)
         edges.delete(id)
       end
 
-      def to_dot
-        edges.map do |to, edges|
-          edges.map do |edge|
-            "\"#{id}\" -> \"#{to}\" [#{edge.to_dot}]"
-          end
-        end.flatten.join("\n  ")
-      end
-
       def inspect
         "#<#{self.class.name} id=#{id} attributes=#{attributes.map { |k, v| "#{k}: #{v}" }.join(',')} edges=#{edges.count}>"
       end

spec/mosaik/graph/graph_spec.rb

@@ -201,6 +201,27 @@
     end
   end
 
+  describe "#to_dot" do
+    context "when the graph is directed" do
+      subject(:graph) { build(:graph, directed: true) }
+
+      it "returns the graph in DOT format" do
+        graph.add_vertex("vertex1")
+        graph.add_vertex("vertex2")
+        graph.add_vertex("vertex3")
+        graph.add_edge("vertex1", "vertex2")
+        graph.add_edge("vertex2", "vertex3", foo: "bar", baz: "bat")
+
+        expect(graph.to_dot).to eq <<~DOT
+          digraph {
+            "vertex1" -> "vertex2" []
+            "vertex2" -> "vertex3" [foo=bar,baz=bat]
+          }
+        DOT
+      end
+    end
+  end
+
   describe "#tsort" do
     it "topologically sorts the vertices" do
       graph.add_vertex("vertex1")