diff --git a/luxtronik/parameters.py b/luxtronik/parameters.py
index 7286794..2826a52 100755
--- a/luxtronik/parameters.py
+++ b/luxtronik/parameters.py
@@ -1169,7 +1169,7 @@ def __init__(self, safe=True):
     def set(self, target, value):
         """Set parameter to new value."""
         index, parameter = self._lookup(target, with_index=True)
-        if index:
+        if index is not None:
             if parameter.writeable or not self.safe:
                 self.queue[index] = parameter.to_heatpump(value)
             else:
diff --git a/tests/test_calculations.py b/tests/test_calculations.py
new file mode 100644
index 0000000..a769e66
--- /dev/null
+++ b/tests/test_calculations.py
@@ -0,0 +1,14 @@
+"""Test suite for parameters module"""
+
+# pylint: disable=too-few-public-methods
+
+from luxtronik.calculations import Calculations
+
+
+class TestCalculations:
+    """Test suite for Calculations"""
+
+    def test_init(self):
+        """Test cases for initialization"""
+        calculations = Calculations()
+        assert calculations.name == "Calculation"
diff --git a/tests/test_parameters.py b/tests/test_parameters.py
index 1b9c42a..feccf3e 100644
--- a/tests/test_parameters.py
+++ b/tests/test_parameters.py
@@ -39,9 +39,14 @@ def test__lookup(self):
         assert parameters._lookup("0", True) == (0, p0)
         assert parameters._lookup(s, True) == (0, p0)
 
+        # Look for a name which does not exist
         s = "ID_BarFoo"
         assert parameters._lookup(s, True)[0] is None
 
+        # Look for something which is not an int and not a string
+        j = 0.0
+        assert parameters._lookup(j) is None
+
     def test_parse(self):
         """Test cases for _parse"""
         parameters = Parameters()
@@ -53,3 +58,37 @@ def test_parse(self):
         p = parameters.get(n)
 
         assert p.name == f"Unknown_Parameter_{n}"
+
+    def test___iter__(self):
+        """Test cases for __iter__"""
+        parameters = Parameters()
+
+        for i, p in parameters:
+            if i == 0:
+                assert p.name == "ID_Transfert_LuxNet"
+            elif i == 1:
+                assert p.name == "ID_Einst_WK_akt"
+            else:
+                break
+
+    def test_set(self):
+        """Test cases for set"""
+        parameters = Parameters()
+
+        # Set something which does not exist
+        parameters.set("BarFoo", 0)
+        assert len(parameters.queue) == 0
+
+        # Set something which is not allowed to be set
+        parameters.set("ID_Transfert_LuxNet", 0)
+        assert len(parameters.queue) == 0
+
+        # Set something which is allowed to be set
+        parameters.set("ID_Einst_WK_akt", 0)
+        assert len(parameters.queue) == 1
+
+        parameters = Parameters(safe=False)
+
+        # Set something which is not allowed to be set, but we are brave.
+        parameters.set("ID_Transfert_LuxNet", 0)
+        assert len(parameters.queue) == 1
diff --git a/tests/test_visibilities.py b/tests/test_visibilities.py
new file mode 100644
index 0000000..47bc22f
--- /dev/null
+++ b/tests/test_visibilities.py
@@ -0,0 +1,14 @@
+"""Test suite for parameters module"""
+
+# pylint: disable=too-few-public-methods
+
+from luxtronik.visibilities import Visibilities
+
+
+class TestVisibilities:
+    """Test suite for Visibilities"""
+
+    def test_init(self):
+        """Test cases for initialization"""
+        visibilities = Visibilities()
+        assert visibilities.name == "Visibility"