diff --git a/README.md b/README.md
index fccc9c2a89ea5fa5b9d873e6473e28fe3064c1fb..81046b767abc8c0de65832b7e4dc0cc07299c668 100644
--- a/README.md
+++ b/README.md
@@ -9,18 +9,14 @@ This has the MFIX-Exa repo as a submodule in order to test against existing ``in
 
 ## Build
 
-> python3 pip install cmake # if CMake not installed
-> cmake -S. -Bbuild
-> cmake --build build
-> cd build
-> ctest
+> python3 pip install meson ninja
+> meson build
+> ninja -C build
 
 ## Run Tests
 
-> cmake --build build --target unit_tests
-> ./build/src/tests/unit_tests
+> meson test -C build
 
 ## Run on inputs file
 
-> cmake --build build --target mfix-parser
-> ./build/mfix-parser subprojects/mfix/benchmarks/01-HCS/Size0001/inputs && echo "Parsing succeeded."
+> ./build/src/mfix-parser subprojects/mfix/benchmarks/01-HCS/Size0001/inputs && echo "Parsing succeeded."
diff --git a/src/inputs_file.cpp b/src/inputs_file.cpp
index 4117db3766058ed2d399feff2a063deaa5777fd6..95f50d5ee5e284cce387078c2521ba5ac2cae4c3 100644
--- a/src/inputs_file.cpp
+++ b/src/inputs_file.cpp
@@ -27,10 +27,9 @@ solver_settings::SolverSettings InputsFile::load() {
   // for (auto it = inputinfo.begin(); it != inputinfo.end(); ++it) {
   //   std::visit(
   //       overloaded{
-  //           [](std::string ss) { std::cout << ss << std::endl; },
-  //           [](parser::NumberArray aa) { std::cout << aa.size() << std::endl;
+  //           [it](parser::NumberArray aa) { std::cout <<  it->first << " nums " << aa.size() << std::endl;
   //           },
-  //           [](parser::StringArray aa) { std::cout << aa.size() << std::endl;
+  //           [it](parser::StringArray aa) { std::cout <<  it->first << " strings " << aa.size() << std::endl;
   //           },
   //       },
   //       it->second);
diff --git a/src/solver.cpp b/src/solver.cpp
index a95db811ee0d998268ac3bfb3c1455f38ee3ce51..3b11fcb9857b12ed335cbdd5a5ffed464aa17928 100644
--- a/src/solver.cpp
+++ b/src/solver.cpp
@@ -5,21 +5,44 @@
 
 namespace {
 
-void require(parser::InputInfo ii, std::string key) {
-  if (!ii.count(key)) {
+void require(std::string key) {
     std::cout << "missing required key:  " << key << std::endl;
-  }
 }
 
 std::optional<solver_settings::SolverSettings>
 do_make_solver(parser::InputInfo ii) {
   solver_settings::SolverSettings ss;
-  require(ii, "geometry.prob_lo");
-  require(ii, "geometry.prob_hi");
-  require(ii, "geometry.is_periodic");
-  auto lows = std::get<parser::NumberArray>(ii["geometry.prob_lo"]);
-  auto highs = std::get<parser::NumberArray>(ii["geometry.prob_hi"]);
-  auto is_periodic = std::get<parser::NumberArray>(ii["geometry.is_periodic"]);
+  std::string PROB_LO("geometry.prob_lo");
+  std::string PROB_HI("geometry.prob_hi");
+  std::string PERIODIC("geometry.is_periodic");
+  if (!ii.count(PROB_LO)) {
+    require(PROB_LO);
+    return std::nullopt;
+  }
+  if (!ii.count(PROB_HI)) {
+    require(PROB_HI);
+    return std::nullopt;
+  }
+  if (!ii.count(PERIODIC)) {
+    require(PERIODIC);
+    return std::nullopt;
+  }
+  auto lows = std::get<parser::NumberArray>(ii[PROB_LO]);
+  auto highs = std::get<parser::NumberArray>(ii[PROB_HI]);
+  auto is_periodic = std::get<parser::NumberArray>(ii[PERIODIC]);
+  if (lows.size() != 3) {
+    std::cout << "prob_lo needs 3 elements " << std::endl;
+    return std::nullopt;
+  }
+  if (highs.size() != 3) {
+    std::cout << "prob_hi needs 3 elements " << std::endl;
+    return std::nullopt;
+  }
+  if (is_periodic.size() != 3) {
+    std::cout << "periodic needs 3 elements " << std::endl;
+    return std::nullopt;
+  }
+
   std::get<0>(ss.geometry.axes).high = highs[0];
   std::get<0>(ss.geometry.axes).low = lows[0];
   std::get<0>(ss.geometry.axes).periodic = is_periodic[0];
diff --git a/tests/meson.build b/tests/meson.build
index f0b783875204036a25a326edfc9ee1980d8b539b..71787c4c824433dd1f3e51911f9de489d5723072 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -1,10 +1,17 @@
 unit_exe = executable('unit_tests',
-                      'inputs.t.cpp',
                       'parser.t.cpp',
                       'solver.t.cpp',
                       'main.cpp',
                       include_directories: [parser_inc, catch2_inc],
                       link_with: lib_parser
                      )
-
 test('unit_test', unit_exe)
+
+
+functional_test = executable('functional_tests',
+                      'inputs.t.cpp',
+                      'main.cpp',
+                      include_directories: [parser_inc, catch2_inc],
+                      link_with: lib_parser
+                     )
+test('functional_test', functional_test)
diff --git a/tests/solver.t.cpp b/tests/solver.t.cpp
index 104110b20ca2bca73d9a84539b2a02aecf662fa4..53421740dcd1dae77373a1a18ca1895041034837 100644
--- a/tests/solver.t.cpp
+++ b/tests/solver.t.cpp
@@ -4,11 +4,24 @@
 
 #include <inputs.hpp>
 
+std::string PROB_LO("geometry.prob_lo");
+std::string PROB_HI("geometry.prob_hi");
+std::string PERIODIC("geometry.is_periodic");
+
+TEST_CASE("empty (invalid) map", "[]") {
+  parser::InputInfo ii;
+  auto maybe_sv = solver_settings::make_solver(ii);
+  CHECK_FALSE(maybe_sv.has_value());
+}
+
 TEST_CASE("from_origin", "[]") {
   parser::InputInfo ii;
-  ii["geometry.prob_lo"] = parser::NumberArray({0, 0, 0});
-  ii["geometry.prob_hi"] = parser::NumberArray({0.004, 0.001, 0.001});
-  ii["geometry.is_periodic"] = parser::NumberArray({0, 0, 0});
+  ii[PROB_LO] = parser::NumberArray({0, 0, 0});
+  ii[PROB_HI] = parser::NumberArray({0.004, 0.001, 0.001});
+  ii[PERIODIC] = parser::NumberArray({0, 0, 0});
+  CHECK(ii.count(PROB_LO));
+  CHECK(ii.count(PROB_HI));
+  CHECK(ii.count(PERIODIC));
   auto maybe_sv = solver_settings::make_solver(ii);
 
   REQUIRE(maybe_sv.has_value());
@@ -27,9 +40,9 @@ TEST_CASE("from_origin", "[]") {
 
 TEST_CASE("negative_positive", "[]") {
   parser::InputInfo ii;
-  ii["geometry.prob_lo"] = std::vector<double>({-4, -5, -6});
-  ii["geometry.prob_hi"] = std::vector<double>({11.1, 22.2, 33.3});
-  ii["geometry.is_periodic"] = parser::NumberArray({1, 0, 1});
+  ii[PROB_LO] = std::vector<double>({-4, -5, -6});
+  ii[PROB_HI] = std::vector<double>({11.1, 22.2, 33.3});
+  ii[PERIODIC] = parser::NumberArray({1, 0, 1});
 
   auto maybe_sv = solver_settings::make_solver(ii);