Added unittest for cosineFunction

src/test/c/test_taschenrechner.c

@@ -120,4 +120,12 @@ void test_sineFunction(void) {
     TEST_ASSERT_EQUAL_FLOAT(0.0, sineFunction(0.0));
 }
 
+// Cosine function
+void test_cosineFunction(void) {
+    // Your test code here
+    TEST_ASSERT_EQUAL_FLOAT(1.0, cosineFunction(0.0));
+}
+
+
+
 #endif // TEST