diff --git a/tests/composition/compositionTest.cpp b/tests/composition/compositionTest.cpp
index 1336983..5bd2a3d 100644
--- a/tests/composition/compositionTest.cpp
+++ b/tests/composition/compositionTest.cpp
@@ -3,8 +3,10 @@
 #include <algorithm>
 
 #include "atomicSpecies.h"
+#include "composition.h"
+#include "config.h"
 
-std::string EXAMPLE_FILENAME = std::string(getenv("MESON_SOURCE_ROOT")) + "/tests/composition/example.yaml";
+std::string EXAMPLE_FILENAME = std::string(getenv("MESON_SOURCE_ROOT")) + "/tests/config/example.yaml";
 
 /**
  * @brief Test suite for the composition class.
@@ -14,8 +16,56 @@ class compositionTest : public ::testing::Test {};
 /**
  * @brief Test the constructor of the composition class.
  */
-TEST_F(compositionTest, constructor) {
-    std::cout << "Testing the constructor of the composition class." << std::endl;
-    std::cout << chemSpecies::species.at("H-1") << std::endl;
+TEST_F(compositionTest, isotopeMasses) {
+    EXPECT_NO_THROW(chemSpecies::species.at("H-1"));
+    EXPECT_DOUBLE_EQ(chemSpecies::species.at("H-1").mass(), 1.007825031898);
+    EXPECT_DOUBLE_EQ(chemSpecies::species.at("He-3").mass(), 3.0160293219700001);
+    EXPECT_DOUBLE_EQ(chemSpecies::species.at("He-4").mass(),4.0026032541300003);
 }
 
+TEST_F(compositionTest, constructor) {
+    Config::getInstance().loadConfig(EXAMPLE_FILENAME);
+    EXPECT_NO_THROW(composition::Composition comp);
+}
+
+TEST_F(compositionTest, registerSymbol) {
+    Config::getInstance().loadConfig(EXAMPLE_FILENAME);
+    composition::Composition comp;
+    EXPECT_NO_THROW(comp.registerSymbol("H-1"));
+    EXPECT_NO_THROW(comp.registerSymbol("He-4"));
+    EXPECT_THROW(comp.registerSymbol("H-19"), std::runtime_error);
+    EXPECT_THROW(comp.registerSymbol("He-21"), std::runtime_error);
+
+    std::set<std::string> registeredSymbols = comp.getRegisteredSymbols();
+    EXPECT_TRUE(registeredSymbols.find("H-1") != registeredSymbols.end());
+    EXPECT_TRUE(registeredSymbols.find("He-4") != registeredSymbols.end());
+    EXPECT_TRUE(registeredSymbols.find("H-19") == registeredSymbols.end());
+    EXPECT_TRUE(registeredSymbols.find("He-21") == registeredSymbols.end());
+}
+
+TEST_F(compositionTest, setGetComposition) {
+    Config::getInstance().loadConfig(EXAMPLE_FILENAME);
+    composition::Composition comp;
+    comp.registerSymbol("H-1");
+    comp.registerSymbol("He-4");
+
+    EXPECT_DOUBLE_EQ(comp.setComposition("H-1", 0.5), 0.0);
+    EXPECT_DOUBLE_EQ(comp.setComposition("He-4", 0.5), 0.0);
+    EXPECT_DOUBLE_EQ(comp.setComposition("H-1", 0.6), 0.5);
+    EXPECT_DOUBLE_EQ(comp.setComposition("He-4", 0.4), 0.5);
+
+    EXPECT_NO_THROW(comp.finalize());
+    std::unordered_map<std::string, composition::CompositionEntry> compositions = comp.getCompositions();
+    EXPECT_DOUBLE_EQ(compositions["H-1"].mass_fraction, 0.6);
+
+    EXPECT_THROW(comp.setComposition("He-3", 0.3), std::runtime_error);
+
+    EXPECT_NO_THROW(comp.setComposition({"H-1", "He-4"}, {0.5, 0.5}));
+    EXPECT_THROW(comp.getComposition("H-1"), std::runtime_error);
+    EXPECT_TRUE(comp.finalize());
+    EXPECT_DOUBLE_EQ(comp.getComposition("H-1").mass_fraction, 0.5);
+
+    EXPECT_NO_THROW(comp.setComposition({"H-1", "He-4"}, {0.6, 0.6}));
+    EXPECT_FALSE(comp.finalize());
+    EXPECT_THROW(comp.getComposition("H-1"), std::runtime_error);
+}
\ No newline at end of file
diff --git a/tests/composition/meson.build b/tests/composition/meson.build
index a5b6889..4819521 100644
--- a/tests/composition/meson.build
+++ b/tests/composition/meson.build
@@ -11,7 +11,7 @@ foreach test_file : test_sources
   test_exe = executable(
       exe_name,
       test_file,
-      dependencies: [gtest_dep, species_weight_dep, gtest_main],
+      dependencies: [gtest_dep, species_weight_dep, gtest_main, composition_dep],
       install_rpath: '@loader_path/../../src'  # Ensure runtime library path resolves correctly
   )