diff --git a/src/main/java/tdd/setup/Calculator.java b/src/main/java/tdd/setup/Calculator.java
index 171f6d6..e3cc4b9 100644
--- a/src/main/java/tdd/setup/Calculator.java
+++ b/src/main/java/tdd/setup/Calculator.java
@@ -19,7 +19,11 @@ public void pressDigitKey(int digit) {
             screen = screen + digit;
         } else {
             latestValue = Double.parseDouble(screen);
-            screen = Integer.toString(digit);
+            if(!screen.contains(".")){
+                screen = Integer.toString(digit);
+            } else {
+                screen = "0" + "." + digit;
+            }
         }
     }
 
@@ -34,11 +38,14 @@ public void pressOperationKey(String operation)  {
     }
 
     public void pressDotKey() {
-        if(!screen.endsWith(".")) screen = screen + ".";
+        if(!screen.contains(".")) screen = screen + ".";
     }
 
     public void pressNegative() {
         screen = screen.startsWith("-") ? screen.substring(1) : "-" + screen;
+        if (screen.equals("-" + "0")) {
+            screen = "0";
+        }
     }
 
     public void pressEquals() {
diff --git a/src/test/java/tdd/setup/CalculatorTest.java b/src/test/java/tdd/setup/CalculatorTest.java
index 3bf16e9..2133080 100644
--- a/src/test/java/tdd/setup/CalculatorTest.java
+++ b/src/test/java/tdd/setup/CalculatorTest.java
@@ -16,4 +16,42 @@ void calculatorCanDoTwoPlusTwo() {
         calc.pressEquals();
         assertEquals("4", calc.readScreen());
     }
+
+    @Test
+    @DisplayName("should display result after pressing clear key")
+    void calculatorCanDisplayZeroResult() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(1);
+        calc.pressOperationKey("+");
+        calc.pressDigitKey(2);
+        calc.pressEquals();
+        calc.pressClearKey();
+        assertEquals("0", calc.readScreen());
+    }
+
+    @Test
+    @DisplayName("should display result after multiplying two decimal numbers")
+    void calculatorCanDoZeroCommaTwoTimesZeroCommaThree() {
+        Calculator calc = new Calculator();
+        calc.pressDotKey();
+        calc.pressDigitKey(2);
+        calc.pressOperationKey("x");
+        calc.pressDotKey();
+        calc.pressDigitKey(3);
+        calc.pressEquals();
+        assertEquals("0.06", calc.readScreen());
+    }
+
+    @Test
+    @DisplayName("should display result after multiplying a negative button with a positive number")
+    void calculatorCanDoNegativeButtonTimesThree() {
+        Calculator calc = new Calculator();
+        calc.pressNegative();
+        calc.pressOperationKey("x");
+        calc.pressDigitKey(3);
+        calc.pressEquals();
+        assertEquals("0", calc.readScreen());
+    }
 }
+
+