public ReportResult RunTests()
        {
            ReportResult result = new ReportResult();
            if (graph.VerticesCount == 0)
            {
                this.OnLog("No assembly to execute");
                result.UpdateCounts();
                return result;
            }

            this.OnLog("Sorting assemblies by dependencies");
            // create topological sort
            ArrayList sortedVertices = new ArrayList();
            TopologicalSortAlgorithm topo = new TopologicalSortAlgorithm(graph);
            topo.Compute(sortedVertices);
            if (sortedVertices.Count == 0)
                throw new InvalidOperationException("Cannot be zero");

            // set vertices colors
            this.OnLog("etting up fixture colors");
            VertexColorDictionary colors = new VertexColorDictionary();
            foreach (TestDomainVertex v in graph.Vertices)
                colors.Add(v, GraphColor.White);

            // execute each domain
            foreach (TestDomainVertex v in sortedVertices)
            {
                // if vertex color is not white, skip it
                GraphColor color = colors[v];
                if (color != GraphColor.White)
                {
                    this.OnLog("Skipping assembly {0} because dependent assembly failed", v.Domain.TestEngine.Explorer.AssemblyName);
                    // mark children
                    foreach (TestDomainVertex child in graph.AdjacentVertices(v))
                        colors[child] = GraphColor.Black;
                    continue;
                }

                this.OnLog("Loading {0}", v.Domain.TestEngine.Explorer.AssemblyName);

                ReportCounter counter = v.Domain.TestEngine.GetTestCount();
                this.OnLog("Found  {0} tests", counter.RunCount);
                this.OnLog("Running fixtures.");
                v.Domain.TestEngine.RunPipes();
                counter = v.Domain.TestEngine.GetTestCount();
                this.OnLog("Tests finished: {0} tests, {1} success, {2} failures, {3} ignored"
                    , counter.RunCount
                    , counter.SuccessCount
                    , counter.FailureCount
                    , counter.IgnoreCount
                    );

                result.Merge(v.Domain.TestEngine.Report.Result);

                if (counter.FailureCount != 0)
                {
                    // mark children as failed
                    colors[v] = GraphColor.Black;
                    foreach (TestDomainVertex child in graph.AdjacentVertices(v))
                        colors[child] = GraphColor.Black;
                }
                else
                {
                    // mark vertex as succesfull
                    colors[v] = GraphColor.Gray;
                }
            }

            result.UpdateCounts();
            MbUnit.Framework.Assert.IsNotNull(result);
            MbUnit.Framework.Assert.IsNotNull(result.Counter);

            this.OnLog("All Tests finished: {0} tests, {1} success, {2} failures, {3} ignored in {4} seconds"
                , result.Counter.RunCount
                , result.Counter.SuccessCount
                , result.Counter.FailureCount
                , result.Counter.IgnoreCount
                , result.Counter.Duration
                );

            return result;
        }