diff --git a/src/main/java/tdd/setup/Calculator.java b/src/main/java/tdd/setup/Calculator.java
index 171f6d6..cb29a17 100644
--- a/src/main/java/tdd/setup/Calculator.java
+++ b/src/main/java/tdd/setup/Calculator.java
@@ -3,7 +3,7 @@
 // behaviour inspired by https://www.online-calculator.com/
 public class Calculator {
 
-    private String screen = "0";
+    private String screen = "";
 
     private double latestValue;
 
@@ -47,6 +47,7 @@ public void pressEquals() {
             case "-" -> latestValue - Double.parseDouble(screen);
             case "x" -> latestValue * Double.parseDouble(screen);
             case "/" -> latestValue / Double.parseDouble(screen);
+            case "" -> Double.parseDouble(screen);
             default -> throw new IllegalArgumentException();
         };
         screen = Double.toString(result);
diff --git a/src/test/java/tdd/setup/CalculatorTest.java b/src/test/java/tdd/setup/CalculatorTest.java
index 3bf16e9..6c7dde8 100644
--- a/src/test/java/tdd/setup/CalculatorTest.java
+++ b/src/test/java/tdd/setup/CalculatorTest.java
@@ -16,4 +16,36 @@ void calculatorCanDoTwoPlusTwo() {
         calc.pressEquals();
         assertEquals("4", calc.readScreen());
     }
-}
+
+    @Test
+    @DisplayName("should display result 3")
+    void calculatorCanDoFiveMinusTwo() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(5);
+        calc.pressOperationKey("-");
+        calc.pressDigitKey(2);
+        System.out.println(calc.readScreen());
+        calc.pressEquals();
+        assertEquals("3", calc.readScreen());
+    }
+
+    @Test
+    @DisplayName("should display result 5.5")
+    void calculatorCanShowDecimal() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(5);
+        calc.pressDotKey();
+        calc.pressDigitKey(5);
+        System.out.println(calc.readScreen());
+        assertEquals("5.5", calc.readScreen());
+    }
+
+    @Test
+    @DisplayName("should display same digit after pressing Equals without an operation")
+    void calculatorCanDoFourEquals() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(5);
+        calc.pressEquals();
+        assertEquals("5", calc.readScreen());
+    }
+}
\ No newline at end of file