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 84c04f2..14a9790 100644
--- a/app/src/main/java/htw/berlin/prog2/ha1/Calculator.java
+++ b/app/src/main/java/htw/berlin/prog2/ha1/Calculator.java
@@ -72,8 +72,8 @@ public void pressBinaryOperationKey(String operation)  {
      * @param operation "√" für Quadratwurzel, "%" für Prozent, "1/x" für Inversion
      */
     public void pressUnaryOperationKey(String operation) {
-        latestValue = Double.parseDouble(screen);
-        latestOperation = operation;
+        //latestValue = Double.parseDouble(screen);
+        //latestOperation = operation;
         var result = switch(operation) {
             case "√" -> Math.sqrt(Double.parseDouble(screen));
             case "%" -> Double.parseDouble(screen) / 100;
@@ -83,7 +83,7 @@ public void pressUnaryOperationKey(String operation) {
         screen = Double.toString(result);
         if(screen.equals("NaN")) screen = "Error";
         if(screen.contains(".") && screen.length() > 11) screen = screen.substring(0, 10);
-
+        if(screen.equals("Infinity")) screen = "Error";
     }
 
     /**
@@ -130,4 +130,4 @@ public void pressEqualsKey() {
         if(screen.endsWith(".0")) screen = screen.substring(0,screen.length()-2);
         if(screen.contains(".") && screen.length() > 11) screen = screen.substring(0, 10);
     }
-}
+}
\ No newline at end of file
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 ddff0da..287d04c 100644
--- a/app/src/test/java/htw/berlin/prog2/ha1/CalculatorTest.java
+++ b/app/src/test/java/htw/berlin/prog2/ha1/CalculatorTest.java
@@ -90,5 +90,50 @@ void testMultipleDecimalDots() {
 
 
     //TODO hier weitere Tests erstellen
-}
 
+    // Aufgabe1
+    @Test
+    @DisplayName("should display result after minus two positive multi-digit numbers")
+    void testPositiveMinus() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(3);
+        calc.pressDigitKey(0);
+        calc.pressBinaryOperationKey("-");
+        calc.pressDigitKey(1);
+        calc.pressDigitKey(0);
+        calc.pressEqualsKey();
+
+        String expected = "20";
+        String actual = calc.readScreen();
+
+        assertEquals(expected, actual);
+    }
+
+    //Aufgabe2 roter Test
+    @Test
+    @DisplayName("should display Error when trying to calculate 1/0")
+    void testInvertofZero(){
+        Calculator calculator = new Calculator();
+        calculator.pressDigitKey(0);
+        calculator.pressUnaryOperationKey("1/x");
+        String expected = "Error";
+        String actual = calculator.readScreen();
+        assertEquals(expected, actual);
+
+    }
+
+    // zweiter roter Test.
+    @Test
+    @DisplayName("schould display result when calculate Binary plus Unary ")
+    void testResultCalculateOfBinaryplusUnary(){
+        Calculator calculator = new Calculator();
+        calculator.pressDigitKey(5);
+        calculator.pressBinaryOperationKey("+");
+        calculator.pressDigitKey(4);
+        calculator.pressUnaryOperationKey("√");
+        calculator.pressEqualsKey();
+        String expected = "7";
+        String actual = calculator.readScreen();
+        assertEquals(expected, actual);
+    }
+}