feat(shell-surface-pressure-load): step 5 - integrate-nonlinear-follower-pressure

tests/integration/app/shell_surface_pressure_application_test.cpp

@@ -101,6 +101,38 @@ All, 1, 6
          dsload + "*End Step\n";
 }
 
+std::string NonlinearShellDeck() {
+  return R"inp(*Part, name=ShellPart
+*Node
+1, 0., 0., 0.
+2, 1., 0., 0.
+3, 1., 1., 0.
+4, 0., 1., 0.
+*Element, type=S4
+1, 1, 2, 3, 4
+*Elset, elset=ShellSet
+1
+*Shell Section, elset=ShellSet, material=Steel
+0.1
+*End Part
+*Assembly, name=Assembly
+*Instance, name=Shell-1, part=ShellPart
+*End Instance
+*Nset, nset=All, instance=Shell-1
+1, 2, 3, 4
+*End Assembly
+*Material, name=Steel
+*Elastic
+1000., 0.25
+*Boundary
+All, 1, 6
+*Step, name=Step-1, nlgeom=YES
+*Static
+0.1, 1., 0.001, 0.1
+*End Step
+)inp";
+}
+
 }  // namespace
 
 TEST(ShellSurfacePressureApplication,
@@ -143,3 +175,21 @@ TEST(ShellSurfacePressureApplication,
             0);
   EXPECT_GE(H5Fclose(file), 0);
 }
+
+TEST(ShellSurfacePressureApplication,
+     InputWithoutPressureRetainsExistingNonlinearBehavior) {
+  TempDirectory directory{"nonlinear-no-pressure"};
+  const auto input = directory.Path() / "nonlinear-no-pressure.inp";
+  const auto output = directory.Path() / "nonlinear-no-pressure_results.h5";
+  WriteText(input, NonlinearShellDeck());
+
+  EXPECT_EQ(fesa::FesaApplication{}.Run({input.string()}), 0);
+  ASSERT_TRUE(std::filesystem::exists(output));
+  ASSERT_GT(H5Fis_hdf5(output.string().c_str()), 0);
+  const hid_t file =
+      H5Fopen(output.string().c_str(), H5F_ACC_RDONLY, H5P_DEFAULT);
+  ASSERT_GE(file, 0);
+  EXPECT_GT(H5Lexists(file, "/steps/Step-1/accepted_frames", H5P_DEFAULT), 0);
+  EXPECT_EQ(H5Lexists(file, "/surface_pressure", H5P_DEFAULT), 0);
+  EXPECT_GE(H5Fclose(file), 0);
+}