diff --git a/src/test/c/test_taschenrechner.c b/src/test/c/test_taschenrechner.c
index 2bdfaf1..f3f7517 100644
--- a/src/test/c/test_taschenrechner.c
+++ b/src/test/c/test_taschenrechner.c
@@ -138,5 +138,10 @@ void test_logarithmFunction(void) {
     TEST_ASSERT_EQUAL_FLOAT(1.0, logarithmFunction(10.0));
 }
 
+// Natural logarithm function
+void test_naturalLogarithmFunction(void) {
+    // Your test code here
+    TEST_ASSERT_EQUAL_FLOAT(0.0, naturalLogarithmFunction(1.0));
+}
 
 #endif // TEST