diff --git a/app/src/main/java/htw/berlin/prog2/ha1/Calculator.java b/app/src/main/java/htw/berlin/prog2/ha1/Calculator.java
index aaef8862..d8ee6236 100644
--- a/app/src/main/java/htw/berlin/prog2/ha1/Calculator.java
+++ b/app/src/main/java/htw/berlin/prog2/ha1/Calculator.java
@@ -1,5 +1,7 @@
 package htw.berlin.prog2.ha1;
 
+import java.text.NumberFormat;
+
 /**
  * Eine Klasse, die das Verhalten des Online Taschenrechners imitiert, welcher auf
  * https://www.online-calculator.com/ aufgerufen werden kann (ohne die Memory-Funktionen)
@@ -78,10 +80,16 @@ public void pressUnaryOperationKey(String operation) {
             case "√" -> Math.sqrt(Double.parseDouble(screen));
             case "%" -> Double.parseDouble(screen) / 100;
             case "1/x" -> 1 / Double.parseDouble(screen);
+            case "recip" -> (1 / (Double.parseDouble(screen)));
             default -> throw new IllegalArgumentException();
         };
-        screen = Double.toString(result);
-        if(screen.contains(".") && screen.length() > 11) screen = screen.substring(0, 10);
+        //screen = Double.toString(result);
+        //if(screen.contains(".") && screen.length() > 11) screen = screen.substring(0, 10);
+
+        // QuellIdee https://www.youtube.com/watch?v=KLvnQhdx4BI Java: formatting numbers with NumberFormat
+        NumberFormat nf = NumberFormat.getNumberInstance(); //initialize numberformat
+        nf.setMaximumFractionDigits(8); //max number of decimal digits
+        screen = nf.format(result);//rounded operation
 
     }
 
@@ -93,7 +101,7 @@ public void pressUnaryOperationKey(String operation) {
      * Beim zweimaligem Drücken, oder wenn bereits ein Trennzeichen angezeigt wird, passiert nichts.
      */
     public void pressDotKey() {
-        if(!screen.endsWith(".")) screen = screen + ".";
+        if(!screen.contains(".")) screen = screen + ".";
     }
 
     /**
diff --git a/app/src/test/java/htw/berlin/prog2/ha1/CalculatorTest.java b/app/src/test/java/htw/berlin/prog2/ha1/CalculatorTest.java
index addc5f26..a458ee0c 100644
--- a/app/src/test/java/htw/berlin/prog2/ha1/CalculatorTest.java
+++ b/app/src/test/java/htw/berlin/prog2/ha1/CalculatorTest.java
@@ -34,12 +34,68 @@ void testSquareRoot() {
         calc.pressDigitKey(2);
         calc.pressUnaryOperationKey("√");
 
-        String expected = "1.41421356";
+        String expected = "1,41421356";
         String actual = calc.readScreen();
 
         assertEquals(expected, actual);
     }
 
     //TODO hier weitere Tests erstellen
+    @Test
+    @DisplayName("should display correct number after pressing digit keys")
+    void testDigitInput() {
+        Calculator calc = new Calculator();
+
+        calc.pressDigitKey(4);
+        calc.pressDigitKey(2);
+
+        String expected = "42";
+        String actual = calc.readScreen();
+
+        assertEquals(expected, actual);
+    }
+    @Test
+    @DisplayName("should clear all latest values and inputs by pressing the CE button")
+    void testClearAllValues() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(2);
+        calc.pressBinaryOperationKey("+");
+        calc.pressClearKey();
+
+        String expected = "0";
+        String actual = calc.readScreen();
+
+        assertEquals(expected, actual);
+    }
+    @Test
+    @DisplayName("should display reciprocal of a number")
+    void testReciprocal() {
+        Calculator calc = new Calculator();
+
+        calc.pressDigitKey(6);
+        calc.pressUnaryOperationKey("recip");
+
+        String expected = "0,16666667";
+        String actual = calc.readScreen();
+
+        assertEquals(expected, actual);
+    }
+    @Test
+    @DisplayName("should display only one decimal point")
+    void testDotKey() {
+        Calculator calc = new Calculator();
+
+        calc.pressDigitKey(6);
+        calc.pressDotKey();
+        calc.pressDigitKey(6);
+        calc.pressDotKey();
+
+        String expected = "6.6";
+        String actual = calc.readScreen();
+        System.out.println(calc.readScreen());
+
+
+        assertEquals(expected, actual);
+    }
 }