diff --git a/tests/WorkArea.cpp b/tests/WorkArea.hpp
similarity index 100%
rename from tests/WorkArea.cpp
rename to tests/WorkArea.hpp
diff --git a/tests/msim/test_msim.cpp b/tests/msim/test_msim.cpp
index be45c8921..bd23657b2 100644
--- a/tests/msim/test_msim.cpp
+++ b/tests/msim/test_msim.cpp
@@ -44,7 +44,7 @@
 #include <opm/input/eclipse/Schedule/Schedule.hpp>
 #include <opm/input/eclipse/EclipseState/SummaryConfig/SummaryConfig.hpp>
 
-#include <tests/WorkArea.cpp>
+#include <tests/WorkArea.hpp>
 
 using namespace Opm;
 
diff --git a/tests/msim/test_msim_ACTIONX.cpp b/tests/msim/test_msim_ACTIONX.cpp
index 3f67e7f22..cdfc03348 100644
--- a/tests/msim/test_msim_ACTIONX.cpp
+++ b/tests/msim/test_msim_ACTIONX.cpp
@@ -45,7 +45,7 @@
 
 #include <opm/output/eclipse/EclipseIO.hpp>
 
-#include <tests/WorkArea.cpp>
+#include <tests/WorkArea.hpp>
 
 using namespace Opm;
 
diff --git a/tests/msim/test_msim_EXIT.cpp b/tests/msim/test_msim_EXIT.cpp
index 6f2d62a3f..b8b9ec988 100644
--- a/tests/msim/test_msim_EXIT.cpp
+++ b/tests/msim/test_msim_EXIT.cpp
@@ -33,7 +33,7 @@
 #include <opm/input/eclipse/Schedule/Schedule.hpp>
 #include <opm/input/eclipse/EclipseState/SummaryConfig/SummaryConfig.hpp>
 
-#include <tests/WorkArea.cpp>
+#include <tests/WorkArea.hpp>
 #include <opm/msim/msim.hpp>
 
 namespace Opm {
diff --git a/tests/parser/EclipseGridTests.cpp b/tests/parser/EclipseGridTests.cpp
index 65a97f717..73daa2ee7 100644
--- a/tests/parser/EclipseGridTests.cpp
+++ b/tests/parser/EclipseGridTests.cpp
@@ -53,7 +53,7 @@
 #include <opm/input/eclipse/Parser/Parser.hpp>
 #include <opm/io/eclipse/EclFile.hpp>
 
-#include "tests/WorkArea.cpp"
+#include "tests/WorkArea.hpp"
 
 
 BOOST_AUTO_TEST_CASE(CreateMissingDIMENS_throws) {
diff --git a/tests/parser/IOConfigTests.cpp b/tests/parser/IOConfigTests.cpp
index 6601669b3..69edacfc9 100644
--- a/tests/parser/IOConfigTests.cpp
+++ b/tests/parser/IOConfigTests.cpp
@@ -30,7 +30,7 @@
 #include <opm/input/eclipse/Parser/Parser.hpp>
 #include <opm/input/eclipse/EclipseState/IOConfig/IOConfig.hpp>
 
-#include "tests/WorkArea.cpp"
+#include "tests/WorkArea.hpp"
 namespace fs = std::filesystem;
 
 using namespace Opm;
diff --git a/tests/parser/ImportTests.cpp b/tests/parser/ImportTests.cpp
index 4d71b309e..117b9ab86 100644
--- a/tests/parser/ImportTests.cpp
+++ b/tests/parser/ImportTests.cpp
@@ -26,7 +26,7 @@
 #include <opm/input/eclipse/Deck/DeckKeyword.hpp>
 #include <opm/input/eclipse/Deck/ImportContainer.hpp>
 #include <opm/input/eclipse/Units/UnitSystem.hpp>
-#include <tests/WorkArea.cpp>
+#include <tests/WorkArea.hpp>
 #include <iostream>
 #include <filesystem>
 #include <fstream>
diff --git a/tests/parser/InitConfigTest.cpp b/tests/parser/InitConfigTest.cpp
index c46d6df42..13a7a5fa6 100644
--- a/tests/parser/InitConfigTest.cpp
+++ b/tests/parser/InitConfigTest.cpp
@@ -28,7 +28,7 @@
 #include <opm/input/eclipse/EclipseState/InitConfig/InitConfig.hpp>
 #include <opm/input/eclipse/Units/Units.hpp>
 
-#include <tests/WorkArea.cpp>
+#include <tests/WorkArea.hpp>
 
 #include <fstream>
 
diff --git a/tests/parser/ScheduleTests.cpp b/tests/parser/ScheduleTests.cpp
index 123f6b7a1..666175254 100644
--- a/tests/parser/ScheduleTests.cpp
+++ b/tests/parser/ScheduleTests.cpp
@@ -71,7 +71,7 @@
 #include <opm/input/eclipse/Schedule/CompletedCells.hpp>
 #include <opm/input/eclipse/Schedule/ScheduleGrid.hpp>
 
-#include "tests/WorkArea.cpp"
+#include "tests/WorkArea.hpp"
 
 using namespace Opm;
 
diff --git a/tests/test_AggregateActionxData.cpp b/tests/test_AggregateActionxData.cpp
index 5518ded51..de5fca806 100644
--- a/tests/test_AggregateActionxData.cpp
+++ b/tests/test_AggregateActionxData.cpp
@@ -51,7 +51,7 @@
 #include <vector>
 #include <fmt/format.h>
 
-#include "tests/WorkArea.cpp"
+#include "tests/WorkArea.hpp"
 
 namespace {
 
diff --git a/tests/test_AggregateUDQData.cpp b/tests/test_AggregateUDQData.cpp
index 9468de412..bcd44c93d 100644
--- a/tests/test_AggregateUDQData.cpp
+++ b/tests/test_AggregateUDQData.cpp
@@ -47,7 +47,7 @@
 #include <string>
 #include <vector>
 
-#include "tests/WorkArea.cpp"
+#include "tests/WorkArea.hpp"
 
 namespace {
 
diff --git a/tests/test_AggregateWellData.cpp b/tests/test_AggregateWellData.cpp
index f7b4d46d7..e8459de0d 100644
--- a/tests/test_AggregateWellData.cpp
+++ b/tests/test_AggregateWellData.cpp
@@ -56,7 +56,7 @@
 #include <utility>
 #include <vector>
 
-#include "tests/WorkArea.cpp"
+#include "tests/WorkArea.hpp"
 
 struct MockIH
 {
diff --git a/tests/test_ERft.cpp b/tests/test_ERft.cpp
index 8fd22fa01..3950f5938 100644
--- a/tests/test_ERft.cpp
+++ b/tests/test_ERft.cpp
@@ -35,7 +35,7 @@
 #include <stdio.h>
 #include <tuple>
 
-#include "tests/WorkArea.cpp"
+#include "tests/WorkArea.hpp"
 
 using namespace Opm::EclIO;
 
diff --git a/tests/test_ERsm.cpp b/tests/test_ERsm.cpp
index f93d05f78..b936008b8 100644
--- a/tests/test_ERsm.cpp
+++ b/tests/test_ERsm.cpp
@@ -22,7 +22,7 @@
 
 #include <fstream>
 #include <opm/io/eclipse/ERsm.hpp>
-#include <tests/WorkArea.cpp>
+#include <tests/WorkArea.hpp>
 #include <opm/common/utility/FileSystem.hpp>
 
 Opm::EclIO::ERsm create(const std::string& rsm_data) {
diff --git a/tests/test_ERst.cpp b/tests/test_ERst.cpp
index 93973dda1..d1a2be843 100644
--- a/tests/test_ERst.cpp
+++ b/tests/test_ERst.cpp
@@ -41,7 +41,7 @@
 
 #include <opm/common/utility/FileSystem.hpp>
 
-#include "tests/WorkArea.cpp"
+#include "tests/WorkArea.hpp"
 
 using namespace Opm::EclIO;
 
diff --git a/tests/test_ESmry.cpp b/tests/test_ESmry.cpp
index 8a0da9cb1..46914b823 100644
--- a/tests/test_ESmry.cpp
+++ b/tests/test_ESmry.cpp
@@ -35,7 +35,7 @@
 #include <math.h>
 #include <stdio.h>
 #include <tuple>
-#include "tests/WorkArea.cpp"
+#include "tests/WorkArea.hpp"
 
 using Opm::EclIO::ESmry;
 
diff --git a/tests/test_EclIO.cpp b/tests/test_EclIO.cpp
index 7e9c5c19e..17a1481ba 100644
--- a/tests/test_EclIO.cpp
+++ b/tests/test_EclIO.cpp
@@ -31,7 +31,7 @@
 
 #include <opm/io/eclipse/EclFile.hpp>
 #include <opm/io/eclipse/EclUtil.hpp>
-#include "WorkArea.cpp"
+#include "WorkArea.hpp"
 
 #include <opm/io/eclipse/EclOutput.hpp>
 
diff --git a/tests/test_EclRegressionTest.cpp b/tests/test_EclRegressionTest.cpp
index c64654a3a..2a78e7252 100644
--- a/tests/test_EclRegressionTest.cpp
+++ b/tests/test_EclRegressionTest.cpp
@@ -31,7 +31,7 @@
 #include <opm/io/eclipse/EclOutput.hpp>
 
 #include <iomanip>
-#include "tests/WorkArea.cpp"
+#include "tests/WorkArea.hpp"
 
 using Opm::EclIO::EGrid;
 using Opm::EclIO::ESmry;
diff --git a/tests/test_EclipseIO.cpp b/tests/test_EclipseIO.cpp
index a0914e391..949b3fc48 100644
--- a/tests/test_EclipseIO.cpp
+++ b/tests/test_EclipseIO.cpp
@@ -55,7 +55,7 @@
 
 #include <time.h>
 
-#include <tests/WorkArea.cpp>
+#include <tests/WorkArea.hpp>
 
 using namespace Opm;
 
diff --git a/tests/test_ExtESmry.cpp b/tests/test_ExtESmry.cpp
index c9991e9c0..7fe2e7d2c 100644
--- a/tests/test_ExtESmry.cpp
+++ b/tests/test_ExtESmry.cpp
@@ -37,7 +37,7 @@
 #include <stdio.h>
 #include <tuple>
 
-#include "tests/WorkArea.cpp"
+#include "tests/WorkArea.hpp"
 
 
 using Opm::EclIO::ESmry;
diff --git a/tests/test_Restart.cpp b/tests/test_Restart.cpp
index 8bb7a0b83..08d499798 100644
--- a/tests/test_Restart.cpp
+++ b/tests/test_Restart.cpp
@@ -55,7 +55,7 @@
 
 #include <opm/common/utility/TimeService.hpp>
 
-#include <tests/WorkArea.cpp>
+#include <tests/WorkArea.hpp>
 
 using namespace Opm;
 
diff --git a/tests/test_Summary.cpp b/tests/test_Summary.cpp
index 9538003fd..9106d3857 100644
--- a/tests/test_Summary.cpp
+++ b/tests/test_Summary.cpp
@@ -57,7 +57,7 @@
 #include <opm/io/eclipse/ESmry.hpp>
 #include <opm/io/eclipse/ERsm.hpp>
 
-#include <tests/WorkArea.cpp>
+#include <tests/WorkArea.hpp>
 
 using namespace Opm;
 using rt = data::Rates::opt;
diff --git a/tests/test_Summary_Group.cpp b/tests/test_Summary_Group.cpp
index 55b8a4a41..d6617e519 100644
--- a/tests/test_Summary_Group.cpp
+++ b/tests/test_Summary_Group.cpp
@@ -54,7 +54,7 @@
 
 #include <opm/io/eclipse/ESmry.hpp>
 
-#include <tests/WorkArea.cpp>
+#include <tests/WorkArea.hpp>
 
 using namespace Opm;
 using rt = data::Rates::opt;
diff --git a/tests/test_restartwellinfo.cpp b/tests/test_restartwellinfo.cpp
index 9c9006e27..c0fb5ba5b 100644
--- a/tests/test_restartwellinfo.cpp
+++ b/tests/test_restartwellinfo.cpp
@@ -47,7 +47,7 @@
 #include <tuple>
 #include <stdio.h>
 
-#include "tests/WorkArea.cpp"
+#include "tests/WorkArea.hpp"
 
 void verifyWellState(const std::string& rst_filename, const Opm::Schedule& schedule) {
 
diff --git a/tests/test_rst.cpp b/tests/test_rst.cpp
index 4b2a7d965..6f5111132 100644
--- a/tests/test_rst.cpp
+++ b/tests/test_rst.cpp
@@ -55,7 +55,7 @@
 #include <opm/io/eclipse/rst/well.hpp>
 #include <opm/io/eclipse/rst/state.hpp>
 
-#include <tests/WorkArea.cpp>
+#include <tests/WorkArea.hpp>
 
 namespace {
     Opm::Deck first_sim()