diff --git a/opm/output/eclipse/AggregateWellData.hpp b/opm/output/eclipse/AggregateWellData.hpp
index 131e18212..f9590981f 100644
--- a/opm/output/eclipse/AggregateWellData.hpp
+++ b/opm/output/eclipse/AggregateWellData.hpp
@@ -33,6 +33,7 @@ namespace Opm {
     class Schedule;
     class SummaryState;
     class UnitSystem;
+    class WellTestState;
     namespace Action {
         class State;
     }
@@ -49,12 +50,13 @@ namespace Opm { namespace RestartIO { namespace Helpers {
     public:
         explicit AggregateWellData(const std::vector<int>& inteHead);
 
-        void captureDeclaredWellData(const Schedule&   	sched,
-                                     const UnitSystem& 		units,
-                                     const std::size_t 		sim_step,
-                                     const ::Opm::Action::State& action_state,
-                                     const ::Opm::SummaryState&  	smry,
-                                     const std::vector<int>& 	inteHead);
+        void captureDeclaredWellData(const Schedule&   	       sched,
+                                     const UnitSystem& 		     units,
+                                     const std::size_t 		     sim_step,
+                                     const Opm::Action::State& action_state,
+                                     const Opm::WellTestState& wtest_state,
+                                     const Opm::SummaryState&  smry,
+                                     const std::vector<int>& 	 inteHead);
 
         void captureDynamicWellData(const Opm::Schedule&        sched,
                                     const std::size_t           sim_step,
diff --git a/src/opm/output/eclipse/AggregateWellData.cpp b/src/opm/output/eclipse/AggregateWellData.cpp
index 337d78a19..4a09805b8 100644
--- a/src/opm/output/eclipse/AggregateWellData.cpp
+++ b/src/opm/output/eclipse/AggregateWellData.cpp
@@ -38,6 +38,8 @@
 #include <opm/parser/eclipse/EclipseState/Schedule/SummaryState.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/VFPProdTable.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/Well/Well.hpp>
+#include <opm/parser/eclipse/EclipseState/Schedule/Well/WellTestConfig.hpp>
+#include <opm/parser/eclipse/EclipseState/Schedule/Well/WellTestState.hpp>
 
 #include <opm/parser/eclipse/Units/UnitSystem.hpp>
 #include <opm/parser/eclipse/Units/Units.hpp>
@@ -970,6 +972,7 @@ captureDeclaredWellData(const Schedule&   sched,
                         const UnitSystem& units,
                         const std::size_t sim_step,
                         const ::Opm::Action::State& action_state,
+                        const Opm::WellTestState& wtest_state,
                         const ::Opm::SummaryState&  smry,
                         const std::vector<int>& inteHead)
 {
diff --git a/src/opm/output/eclipse/RestartIO.cpp b/src/opm/output/eclipse/RestartIO.cpp
index 95cd4818d..5682fdf4a 100644
--- a/src/opm/output/eclipse/RestartIO.cpp
+++ b/src/opm/output/eclipse/RestartIO.cpp
@@ -383,14 +383,14 @@ namespace {
                    const std::vector<std::string>& well_names,
                    const data::Wells&              wells,
                    const Opm::Action::State&       action_state,
+                   const Opm::WellTestState&       wtest_state,
                    const Opm::SummaryState&        sumState,
                    const std::vector<int>&         ih,
                    EclIO::OutputStream::Restart&   rstFile)
     {
         auto wellData = Helpers::AggregateWellData(ih);
-        wellData.captureDeclaredWellData(schedule, units, sim_step, action_state, sumState, ih);
-        wellData.captureDynamicWellData(schedule, sim_step,
-                                        wells, sumState);
+        wellData.captureDeclaredWellData(schedule, units, sim_step, action_state, wtest_state, sumState, ih);
+        wellData.captureDynamicWellData(schedule, sim_step, wells, sumState);
 
         rstFile.write("IWEL", wellData.getIWell());
         rstFile.write("SWEL", wellData.getSWell());
@@ -482,6 +482,7 @@ namespace {
                           const Schedule&                               schedule,
                           const data::Wells&                            wellSol,
                           const Opm::Action::State&                     action_state,
+                          const Opm::WellTestState&                     wtest_state,
                           const Opm::SummaryState&                      sumState,
                           const std::vector<int>&                       inteHD,
                           const data::Aquifers&                         aquDynData,
@@ -514,7 +515,7 @@ namespace {
             }
 
             writeWell(sim_step, ecl_compatible_rst, phases, units, grid, schedule,
-                      wells, wellSol, action_state, sumState, inteHD, rstFile);
+                      wells, wellSol, action_state, wtest_state, sumState, inteHD, rstFile);
         }
 
         if ((es.aquifer().hasAnalyticalAquifer() || es.aquifer().hasNumericalAquifer()) &&
@@ -757,7 +758,7 @@ void save(EclIO::OutputStream::Restart&                 rstFile,
           const EclipseGrid&                            grid,
           const Schedule&                               schedule,
           const Action::State&                          action_state,
-          const WellTestState&                          ,
+          const WellTestState&                          wtest_state,
           const SummaryState&                           sumState,
           const UDQState&                               udqState,
           std::optional<Helpers::AggregateAquiferData>& aquiferData,
@@ -784,7 +785,7 @@ void save(EclIO::OutputStream::Restart&                 rstFile,
 
     if (report_step > 0) {
         writeDynamicData(sim_step, ecl_compatible_rst, es.runspec().phases(),
-                         units, grid, es, schedule, value.wells, action_state,
+                         units, grid, es, schedule, value.wells, action_state, wtest_state,
                          sumState, inteHD, value.aquifer, aquiferData, rstFile);
     }
 
diff --git a/tests/test_AggregateActionxData.cpp b/tests/test_AggregateActionxData.cpp
index 12a7d7cbf..7913558a5 100644
--- a/tests/test_AggregateActionxData.cpp
+++ b/tests/test_AggregateActionxData.cpp
@@ -30,6 +30,7 @@
 #include <opm/parser/eclipse/EclipseState/Schedule/UDQ/UDQParams.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/Action/ActionX.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/Action/ActionContext.hpp>
+#include <opm/parser/eclipse/EclipseState/Schedule/Well/WellTestState.hpp>
 
 #include <opm/parser/eclipse/Units/UnitSystem.hpp>
 #include <opm/parser/eclipse/Units/Units.hpp>
@@ -197,7 +198,7 @@ BOOST_AUTO_TEST_CASE(Declared_Actionx_data)
             }
             {
                 auto well_aggregator = Opm::RestartIO::Helpers::AggregateWellData(ih);
-                well_aggregator.captureDeclaredWellData(sched, es.getUnits(), rptStep, Opm::Action::State {}, st, ih);
+                well_aggregator.captureDeclaredWellData(sched, es.getUnits(), rptStep, {}, {}, st, ih);
                 rstFile.write("IWEL", well_aggregator.getIWell());
                 rstFile.write("SWEL", well_aggregator.getSWell());
                 rstFile.write("XWEL", well_aggregator.getXWell());
diff --git a/tests/test_AggregateUDQData.cpp b/tests/test_AggregateUDQData.cpp
index 20c81e37f..b9f41ae5e 100644
--- a/tests/test_AggregateUDQData.cpp
+++ b/tests/test_AggregateUDQData.cpp
@@ -26,6 +26,7 @@
 #include <opm/parser/eclipse/EclipseState/Schedule/UDQ/UDQState.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/UDQ/UDQSet.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/UDQ/UDQEnums.hpp>
+#include <opm/parser/eclipse/EclipseState/Schedule/Well/WellTestState.hpp>
 
 #include <opm/parser/eclipse/Units/UnitSystem.hpp>
 #include <opm/parser/eclipse/Units/Units.hpp>
@@ -256,8 +257,9 @@ BOOST_AUTO_TEST_CASE (Declared_UDQ_data)
             }
             {
                 auto action_state = Opm::Action::State {};
+                auto wtest_state = Opm::WellTestState{};
                 auto well_aggregator = Opm::RestartIO::Helpers::AggregateWellData(ih);
-                well_aggregator.captureDeclaredWellData(sched, es.getUnits(), rptStep, action_state, st, ih);
+                well_aggregator.captureDeclaredWellData(sched, es.getUnits(), rptStep, action_state, wtest_state, st, ih);
                 rstFile.write("IWEL", well_aggregator.getIWell());
                 rstFile.write("SWEL", well_aggregator.getSWell());
                 rstFile.write("XWEL", well_aggregator.getXWell());
diff --git a/tests/test_AggregateWellData.cpp b/tests/test_AggregateWellData.cpp
index 23952f515..8d968dd35 100644
--- a/tests/test_AggregateWellData.cpp
+++ b/tests/test_AggregateWellData.cpp
@@ -43,6 +43,8 @@
 #include <opm/parser/eclipse/EclipseState/EclipseState.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/Schedule.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/Action/State.hpp>
+#include <opm/parser/eclipse/EclipseState/Schedule/Well/WellTestConfig.hpp>
+#include <opm/parser/eclipse/EclipseState/Schedule/Well/WellTestState.hpp>
 
 #include <exception>
 #include <stdexcept>
@@ -596,6 +598,7 @@ BOOST_AUTO_TEST_CASE (Declared_Well_Data)
 {
     const auto simCase = SimulationCase{first_sim()};
     Opm::Action::State action_state;
+    Opm::WellTestState wtest_state;
     // Report Step 1: 2008-10-10 --> 2011-01-20
     const auto rptStep = std::size_t{1};
 
@@ -608,7 +611,7 @@ BOOST_AUTO_TEST_CASE (Declared_Well_Data)
     const auto smry = sim_state();
     auto awd = Opm::RestartIO::Helpers::AggregateWellData{ih.value};
     awd.captureDeclaredWellData(simCase.sched,
-                                simCase.es.getUnits(), rptStep, action_state, smry, ih.value);
+                                simCase.es.getUnits(), rptStep, action_state, wtest_state, smry, ih.value);
 
     // IWEL (OP_1)
     {
@@ -753,7 +756,7 @@ BOOST_AUTO_TEST_CASE (Declared_Well_Data)
     //smry = sim_state();
     awd = Opm::RestartIO::Helpers::AggregateWellData{ih_8.value};
     awd.captureDeclaredWellData(simCase.sched,
-                                simCase.es.getUnits(), rptStep_8, action_state, smry, ih_8.value);
+                                simCase.es.getUnits(), rptStep_8, action_state, wtest_state, smry, ih_8.value);
     {
         using Ix = ::Opm::RestartIO::Helpers::VectorItems::SWell::index;
 
@@ -779,6 +782,7 @@ BOOST_AUTO_TEST_CASE (Declared_Well_Data_MSW_well_data)
     Opm::EclipseState es    = simCase.es;
     Opm::Schedule     sched = simCase.sched;
     Opm::Action::State action_state;
+    Opm::WellTestState wtest_state;
     const auto rptStep = std::size_t{1};
 
     const auto ih = MockIH {
@@ -788,7 +792,7 @@ BOOST_AUTO_TEST_CASE (Declared_Well_Data_MSW_well_data)
 
     auto awd = Opm::RestartIO::Helpers::AggregateWellData{ih.value};
     awd.captureDeclaredWellData(simCase.sched,
-                                simCase.es.getUnits(), rptStep, action_state, smry, ih.value);
+                                simCase.es.getUnits(), rptStep, action_state, wtest_state, smry, ih.value);
 
     // IWEL (PROD1)
     {
@@ -848,6 +852,7 @@ BOOST_AUTO_TEST_CASE (Dynamic_Well_Data_Step1)
     const auto xw   = well_rates_1();
     const auto smry = sim_state();
     auto awd = Opm::RestartIO::Helpers::AggregateWellData{ih.value};
+    Opm::WellTestState wtest_state;
 
     awd.captureDynamicWellData(simCase.sched, rptStep, xw, smry);
 
@@ -991,6 +996,7 @@ BOOST_AUTO_TEST_CASE (Dynamic_Well_Data_Step2)
     const auto xw   = well_rates_2();
     const auto smry = sim_state();
     auto awd = Opm::RestartIO::Helpers::AggregateWellData{ih.value};
+    Opm::WellTestState wtest_state;
 
     awd.captureDynamicWellData(simCase.sched, rptStep, xw, smry);
 
@@ -1172,6 +1178,7 @@ BOOST_AUTO_TEST_CASE(WELL_POD) {
     const auto rptStep = std::size_t{2};
     const auto sim_step = rptStep - 1;
     Opm::SummaryState sumState(Opm::TimeService::now());
+    Opm::WellTestState wtest_state;
     const auto xw   = well_rates_1();
     Opm::Action::State action_state;
 
@@ -1184,7 +1191,7 @@ BOOST_AUTO_TEST_CASE(WELL_POD) {
                                                             sim_step);
 
     auto wellData = Opm::RestartIO::Helpers::AggregateWellData(ih);
-    wellData.captureDeclaredWellData(simCase.sched, units, sim_step, action_state, sumState, ih);
+    wellData.captureDeclaredWellData(simCase.sched, units, sim_step, action_state, wtest_state, sumState, ih);
     wellData.captureDynamicWellData(simCase.sched, sim_step, xw , sumState);
 
     auto connectionData = Opm::RestartIO::Helpers::AggregateConnectionData(ih);
diff --git a/tests/test_LGOData.cpp b/tests/test_LGOData.cpp
index 0e594acb2..feee1d4a9 100644
--- a/tests/test_LGOData.cpp
+++ b/tests/test_LGOData.cpp
@@ -8,6 +8,7 @@
 #include <opm/parser/eclipse/EclipseState/Schedule/Schedule.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/SummaryState.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/Well/Well.hpp>
+#include <opm/parser/eclipse/EclipseState/Schedule/Well/WellTestState.hpp>
 #include <opm/parser/eclipse/Parser/Parser.hpp>
 
 #include <opm/output/eclipse/AggregateWellData.hpp>
@@ -98,7 +99,7 @@ BOOST_AUTO_TEST_CASE(liftGasOptimzation_data)
     const auto dh = Opm::RestartIO::Helpers::createDoubHead(es, sched, simStep, secs_elapsed, next_step_size);
 
     auto wellData = Opm::RestartIO::Helpers::AggregateWellData(ih);
-    wellData.captureDeclaredWellData(sched, es.getUnits(), simStep, action_state, st, ih);
+    wellData.captureDeclaredWellData(sched, es.getUnits(), simStep, action_state, {}, st, ih);
 
     // intehead data
     auto eachnc = Opm::RestartIO::Helpers::VectorItems::intehead::EACHNCITS;
diff --git a/tests/test_rst.cpp b/tests/test_rst.cpp
index a540da1e8..c57295f2a 100644
--- a/tests/test_rst.cpp
+++ b/tests/test_rst.cpp
@@ -44,6 +44,7 @@
 #include <opm/parser/eclipse/EclipseState/Schedule/Action/State.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/Schedule.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/SummaryState.hpp>
+#include <opm/parser/eclipse/EclipseState/Schedule/Well/WellTestState.hpp>
 
 #include <opm/common/utility/TimeService.hpp>
 
@@ -270,6 +271,7 @@ BOOST_AUTO_TEST_CASE(State_test) {
     const auto sim_step = rptStep - 1;
     Opm::SummaryState sumState(Opm::TimeService::now());
     Opm::Action::State action_state;
+    Opm::WellTestState wtest_state;
 
     const auto ih = Opm::RestartIO::Helpers::createInteHead(simCase.es,
                                                             simCase.grid,
@@ -287,7 +289,7 @@ BOOST_AUTO_TEST_CASE(State_test) {
                                                             0, 0);
 
     auto wellData = Opm::RestartIO::Helpers::AggregateWellData(ih);
-    wellData.captureDeclaredWellData(simCase.sched, units, sim_step, action_state, sumState, ih);
+    wellData.captureDeclaredWellData(simCase.sched, units, sim_step, action_state, wtest_state, sumState, ih);
     wellData.captureDynamicWellData(simCase.sched, sim_step, {} , sumState);
 
     auto connectionData = Opm::RestartIO::Helpers::AggregateConnectionData(ih);