Update the tests to actually call alphar for pures

src/tests/catch_test_multifluid.cxx

@@ -8,12 +8,13 @@
 TEST_CASE("Confirm failure for missing files","[multifluid]") {
     CHECK_THROWS(build_multifluid_model({ "BADFLUID" }, "IMPOSSIBLE PATH", "IMPOSSIBLE PATH.json"));
     CHECK_THROWS(build_multifluid_model({ "BADFLUID" }, "IMPOSSIBLE PATH", "../mycp/dev/mixtures/mixture_binary_pairs.json"));
+    CHECK_THROWS(build_multifluid_model({ "Ethane" }, "IMPOSSIBLE PATH"));
 }
 
 TEST_CASE("Trace critical locus for nitrogen + ethane", "[crit],[multifluid]")
 {
     std::string root = "../mycp";
-    const auto model = build_multifluid_model({ "Nitrogen", "Ethane" }, root, root+"/dev/mixtures/mixture_binary_pairs.json");
+    const auto model = build_multifluid_model({ "Nitrogen", "Ethane" }, root);
 
     for (auto ifluid = 0; ifluid < 2; ++ifluid) {
         double T0 = model.redfunc.Tc[ifluid];
@@ -45,18 +46,25 @@ TEST_CASE("Trace critical locus for nitrogen + ethane", "[crit],[multifluid]")
 TEST_CASE("Check that all pure fluid models can be instantiated", "[multifluid],[all]"){
     std::string root = "../mycp";
     SECTION("With absolute paths to json file") {
+        int counter = 0;
         for (auto path : get_files_in_folder(root + "/dev/fluids", ".json")) {
             if (path.filename().stem() == "Methanol") { continue; }
             CAPTURE(path.string());
             auto abspath = std::filesystem::absolute(path).string();
             auto model = build_multifluid_model({ abspath }, root, root + "/dev/mixtures/mixture_binary_pairs.json");
+            std::valarray<double> z(0.0, 1);
+            model.alphar(300, 1.0, z);
+            counter += 1;
         }
+        CHECK(counter > 100);
     }
     SECTION("With filename stems") {
         for (auto path : get_files_in_folder(root + "/dev/fluids", ".json")) {
             auto stem = path.filename().stem().string(); // filename without the .json
             if (stem == "Methanol") { continue; }
             auto model = build_multifluid_model({ stem }, root, root + "/dev/mixtures/mixture_binary_pairs.json");
+            std::valarray<double> z(0.0, 1);
+            model.alphar(300, 1.0, z);
         }
     }    
 }
@@ -70,5 +78,6 @@ TEST_CASE("Check that mixtures can also do absolute paths", "[multifluid],[abspa
             abspaths.emplace_back(std::filesystem::absolute(p).string());
         }
         auto model = build_multifluid_model(abspaths, root, root + "/dev/mixtures/mixture_binary_pairs.json");
+        auto model2 = build_multifluid_model(abspaths, root); // default path for BIP
     }
 }
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