diff --git a/ApplicationCode/UnitTests/opm-flowdiagnostics-Test.cpp b/ApplicationCode/UnitTests/opm-flowdiagnostics-Test.cpp
index 7da675a1d5..1c8364f392 100644
--- a/ApplicationCode/UnitTests/opm-flowdiagnostics-Test.cpp
+++ b/ApplicationCode/UnitTests/opm-flowdiagnostics-Test.cpp
@@ -3,13 +3,127 @@
 #include <opm/flowdiagnostics/CellSet.hpp>
 #include <opm/utility/graph/AssembledConnections.hpp>
 #include <opm/utility/ECLGraph.hpp>
+#include "opm/utility/ECLWellSolution.hpp"
+#include "opm/flowdiagnostics/ConnectivityGraph.hpp"
+#include "opm/flowdiagnostics/ConnectionValues.hpp"
+#include "opm/flowdiagnostics/CellSetValues.hpp"
+#include "opm/flowdiagnostics/Toolbox.hpp"
+const std::string casePath = "\\\\csfiles\\Store\\ProjectData\\StatoilReservoir\\ReferenceCases\\simple_FlowDiag_Model\\";
+
+Opm::FlowDiagnostics::ConnectionValues
+extractFluxField(const Opm::ECLGraph& G, const int step)
+{
+    using ConnVals = Opm::FlowDiagnostics::ConnectionValues;
+
+    using NConn = ConnVals::NumConnections;
+    using NPhas = ConnVals::NumPhases;
+
+    const auto nconn = NConn{ G.numConnections() };
+    const auto nphas = NPhas{ 3 };
+
+    auto flux = ConnVals(nconn, nphas);
+
+    auto phas = ConnVals::PhaseID{ 0 };
+
+    for(const auto& p :{ Opm::BlackoilPhases::Aqua   ,
+         Opm::BlackoilPhases::Liquid ,
+         Opm::BlackoilPhases::Vapour })
+    {
+        const auto pflux = G.flux(p, step);
+
+        if(! pflux.empty())
+        {
+            assert (pflux.size() == nconn.total);
+
+            auto conn = ConnVals::ConnID{ 0 };
+
+            for(const auto& v : pflux)
+            {
+                flux(conn, phas) = v;
+
+                conn.id += 1;
+            }
+        }
+
+        phas.id += 1;
+    }
+
+    return flux;
+}
+
+Opm::FlowDiagnostics::Toolbox
+initialiseFlowDiagnostics(const Opm::ECLGraph& G,
+                          const std::vector<Opm::ECLWellSolution::WellData>& well_fluxes,
+                          const int step)
+{
+    const auto connGraph = Opm::FlowDiagnostics::
+        ConnectivityGraph{ static_cast<int>(G.numCells()),
+        G.neighbours() };
+
+    using FDT = Opm::FlowDiagnostics::Toolbox;
+
+    auto fl = extractFluxField(G, step);
+    const size_t num_conn = fl.numConnections();
+    const size_t num_phases = fl.numPhases();
+    for(size_t conn = 0; conn < num_conn; ++conn)
+    {
+        using Co = Opm::FlowDiagnostics::ConnectionValues::ConnID;
+        using Ph = Opm::FlowDiagnostics::ConnectionValues::PhaseID;
+        for(size_t phase = 0; phase < num_phases; ++phase)
+        {
+            fl(Co{ conn }, Ph{ phase }) /= 86400; // HACK! converting to SI.
+        }
+    }
+
+    Opm::FlowDiagnostics::CellSetValues inflow;
+    for(const auto& well : well_fluxes)
+    {
+        for(const auto& completion : well.completions)
+        {
+            const int grid_index = completion.grid_index;
+            const auto& ijk = completion.ijk;
+            const int cell_index = G.activeCell(ijk, grid_index);
+            inflow.addCellValue(cell_index, completion.reservoir_inflow_rate);
+        }
+    }
+
+    // Create the Toolbox.
+    auto tool = FDT{ connGraph };
+    tool.assignPoreVolume(G.poreVolume());
+    tool.assignConnectionFlux(fl);
+    tool.assignInflowFlux(inflow);
+
+    return tool;
+}
 
 TEST(opm_flowdiagnostics_test, basic_construction)
 {
     auto g = Opm::AssembledConnections{};
     auto s = Opm::FlowDiagnostics::CellSet{};
-    try {
-    auto eg = Opm::ECLGraph::load("hei", "hopp");
+
+    try 
+    {
+
+        Opm::ECLGraph eclGraph = Opm::ECLGraph::load(casePath + "SIMPLE.EGRID", 
+                                                     casePath + "SIMPLE.INIT");
+        eclGraph.assignFluxDataSource(casePath + "SIMPLE.UNRST");
+
+        Opm::ECLWellSolution wsol(casePath + "SIMPLE.UNRST");
+        auto well_fluxes = wsol.solution(2, eclGraph.numGrids());
+
+
+       // Opm::FlowDiagnostics::ConnectivityGraph connGraph( static_cast<int>(eclGraph.numCells()),
+       //                                                   eclGraph.neighbours() );
+
+
+        auto fdTool = initialiseFlowDiagnostics(eclGraph, well_fluxes, 2);
+
+        // Solve for time of flight.
+        using FDT = Opm::FlowDiagnostics::Toolbox;
+        std::vector<Opm::FlowDiagnostics::CellSet> start;
+        auto sol = fdTool.computeInjectionDiagnostics(start);
+        std::vector<double> globalTimeOfFlight = sol.fd.timeOfFlight();
+
     }
     catch(const std::exception& e)
     {