diff --git a/components/eamxx/src/diagnostics/tests/horiz_avg_test.cpp b/components/eamxx/src/diagnostics/tests/horiz_avg_test.cpp
index f84834d7e7b4..81bc10c6a2c8 100644
--- a/components/eamxx/src/diagnostics/tests/horiz_avg_test.cpp
+++ b/components/eamxx/src/diagnostics/tests/horiz_avg_test.cpp
@@ -33,6 +33,10 @@ TEST_CASE("horiz_avg") {
   using TeamMember = typename TeamPolicy::member_type;
   using KT         = ekat::KokkosTypes<DefaultDevice>;
   using ESU        = ekat::ExeSpaceUtils<typename KT::ExeSpace>;
+
+  // A numerical tolerance
+  auto tol = std::numeric_limits<Real>::epsilon() * 100;
+
   // A world comm
   ekat::Comm comm(MPI_COMM_WORLD);
 
@@ -44,19 +48,17 @@ TEST_CASE("horiz_avg") {
   constexpr int dim3  = 4;
   const int ngcols    = 6 * comm.size();
 
-  auto gm1   = create_gm(comm, ngcols, 1);
-  auto gm2   = create_gm(comm, ngcols, nlevs);
-  auto grid1 = gm1->get_grid("Physics");
-  auto grid2 = gm2->get_grid("Physics");
+  auto gm   = create_gm(comm, ngcols, nlevs);
+  auto grid = gm->get_grid("Physics");
 
   // Input (randomized) qc
   FieldLayout scalar1d_layout{{COL}, {ngcols}};
   FieldLayout scalar2d_layout{{COL, LEV}, {ngcols, nlevs}};
   FieldLayout scalar3d_layout{{COL, CMP, LEV}, {ngcols, dim3, nlevs}};
 
-  FieldIdentifier qc1_fid("qc", scalar1d_layout, kg / kg, grid1->name());
-  FieldIdentifier qc2_fid("qc", scalar2d_layout, kg / kg, grid2->name());
-  FieldIdentifier qc3_fid("qc", scalar3d_layout, kg / kg, grid2->name());
+  FieldIdentifier qc1_fid("qc", scalar1d_layout, kg / kg, grid->name());
+  FieldIdentifier qc2_fid("qc", scalar2d_layout, kg / kg, grid->name());
+  FieldIdentifier qc3_fid("qc", scalar3d_layout, kg / kg, grid->name());
 
   Field qc1(qc1_fid);
   Field qc2(qc2_fid);
@@ -78,8 +80,8 @@ TEST_CASE("horiz_avg") {
   register_diagnostics();
 
   ekat::ParameterList params;
-  // REQUIRE_THROWS(diag_factory.create("HorizAvgDiag", comm,
-  //                                    params));  // No 'field_name' parameter
+  REQUIRE_THROWS(diag_factory.create("HorizAvgDiag", comm,
+                                     params));  // No 'field_name' parameter
 
   // Set time for qc and randomize its values
   qc1.get_header().get_tracking().update_time_stamp(t0);
@@ -90,16 +92,16 @@ TEST_CASE("horiz_avg") {
   randomize(qc3, engine, pdf);
 
   // Create and set up the diagnostic
-  params.set("grid_name", grid1->name());
+  params.set("grid_name", grid->name());
   params.set<std::string>("field_name", "qc");
   auto diag1 = diag_factory.create("HorizAvgDiag", comm, params);
   auto diag2 = diag_factory.create("HorizAvgDiag", comm, params);
   auto diag3 = diag_factory.create("HorizAvgDiag", comm, params);
-  diag1->set_grids(gm1);
-  diag2->set_grids(gm2);
-  diag3->set_grids(gm2);
+  diag1->set_grids(gm);
+  diag2->set_grids(gm);
+  diag3->set_grids(gm);
 
-  auto area = grid1->get_geometry_data("area");
+  auto area = grid->get_geometry_data("area");
 
   diag1->set_required_field(qc1);
   diag1->initialize(t0, RunType::Initial);
@@ -109,7 +111,7 @@ TEST_CASE("horiz_avg") {
 
   FieldIdentifier diag0_fid("qc_horiz_avg_manual",
                             scalar1d_layout.clone().strip_dim(COL), kg / kg,
-                            grid1->name());
+                            grid->name());
   Field diag0(diag0_fid);
   diag0.allocate_view();
   auto diag0_v = diag0.get_view<Real>();
@@ -139,7 +141,9 @@ TEST_CASE("horiz_avg") {
   Kokkos::deep_copy(qc1_v, wavg);
   diag1->compute_diagnostic();
   auto diag1_v2_host = diag1_f.get_view<Real, Host>();
-  REQUIRE(std::abs(diag1_v2_host() - wavg) < sp(1e-6));
+  REQUIRE_THAT(diag1_v2_host(),
+               Catch::Matchers::WithinRel(
+                   wavg, tol));  // Catch2's floating point comparison
 
   // other diags
   // Set qc2_v to 5.0 to get weighted average of 5.0
@@ -155,13 +159,13 @@ TEST_CASE("horiz_avg") {
   auto diag2_v_host = diag2_f.get_view<Real *, Host>();
 
   for(int i = 0; i < nlevs; ++i) {
-    REQUIRE(std::abs(diag2_v_host(i) - wavg) < sp(1e-6));
+    REQUIRE_THAT(diag2_v_host(i), Catch::Matchers::WithinRel(wavg, tol));
   }
 
   auto qc3_v = qc3.get_view<Real ***>();
   FieldIdentifier diag3_manual_fid("qc_horiz_avg_manual",
                                    scalar3d_layout.clone().strip_dim(COL),
-                                   kg / kg, grid2->name());
+                                   kg / kg, grid->name());
   Field diag3_manual(diag3_manual_fid);
   diag3_manual.allocate_view();
   auto diag3_manual_v = diag3_manual.get_view<Real **>();