Added tests for adding and removing edges

spec/ir/directed_graph/directed_graph_spec.rb

@@ -5,8 +5,35 @@
 # This is spec for Directed Graph Library
 
 describe "Directed Graph Utility" do
+
+  before do
+    @graph = DirectedGraph.new
+    @graph.addEdge(1,2,'simple')
+    @graph.addEdge(2,3,'simple')
+    @graph.addEdge(3,4,'simple')
+    @graph.addEdge(4,1,'simple')
+  end
+
   it "should create object of DirectedGraph" do
-    graph = DirectedGraph.new
-    graph.class.should == Java::OrgJrubyIrUtil::DirectedGraph
+    @graph.class.should == Java::OrgJrubyIrUtil::DirectedGraph
+  end
+
+  it "should add an edge to newly created graph" do
+    @graph.edges.size.should == 4
+    @graph.addEdge(4,5,'simple')
+    @graph.edges.size.should == 5
   end
+
+  it "should remove an existing edge from a graph" do
+    @graph.edges.size.should == 4
+    @graph.removeEdge(1,2)
+    @graph.edges.size.should == 3
+  end
+
+  it "should not delete a non-existent edge from the graph" do
+    @graph.edges.size.should == 4
+    @graph.removeEdge(2,1)
+    @graph.edges.size.should == 4
+  end
+
 end