Happy end

src/InsuranceCalculator.java

@@ -1,15 +1,21 @@
 public class InsuranceCalculator {
 
+    private InsuranceStrategy strategy;
+
     public double calculateInsurance(double income) {
+
         if (income <= 10000) {
-            return income*0.365;
+            strategy = new InsuranceStrategyLow();
+            return strategy.calculate(income);
         } else if (income <= 30000) {
-            return (income-10000)*0.2+35600;
+            strategy = new InsuranceStrategyMedium();
+            return strategy.calculate(income);
         } else if (income <= 60000) {
-            return (income-30000)*0.1+76500;
+            strategy = new InsuranceStrategyHigh();
+            return strategy.calculate(income);
         } else {
-            return (income-60000)*0.02+105600;
+            strategy = new InsuranceStrategyVeryHigh();
+            return strategy.calculate(income);
         }
     }
-
 }

src/InsuranceStrategy.java

@@ -0,0 +1,11 @@
+public abstract class InsuranceStrategy {
+    public double calculate(double income) {
+        return (income - getAdjustment()) * getWeight() + getConstant();
+    }
+
+    public abstract int getConstant();
+
+    public abstract double getWeight();
+
+    public abstract int getAdjustment();
+}

src/InsuranceStrategyHigh.java

@@ -0,0 +1,16 @@
+public class InsuranceStrategyHigh extends InsuranceStrategy {
+    @Override
+    public int getConstant() {
+        return 76500;
+    }
+
+    @Override
+    public double getWeight() {
+        return 0.1;
+    }
+
+    @Override
+    public int getAdjustment() {
+        return 30000;
+    }
+}

src/InsuranceStrategyLow.java

@@ -0,0 +1,16 @@
+public class InsuranceStrategyLow extends InsuranceStrategy {
+    @Override
+    public int getConstant() {
+        return 0;
+    }
+
+    @Override
+    public double getWeight() {
+        return 0.365;
+    }
+
+    @Override
+    public int getAdjustment() {
+        return 0;
+    }
+}

src/InsuranceStrategyMedium.java

@@ -0,0 +1,16 @@
+public class InsuranceStrategyMedium extends InsuranceStrategy {
+    @Override
+    public int getConstant() {
+        return 35600;
+    }
+
+    @Override
+    public double getWeight() {
+        return 0.2;
+    }
+
+    @Override
+    public int getAdjustment() {
+        return 10000;
+    }
+}

src/InsuranceStrategyVeryHigh.java

@@ -0,0 +1,19 @@
+public class InsuranceStrategyVeryHigh extends InsuranceStrategy {
+    public InsuranceStrategyVeryHigh() {
+    }
+
+    @Override
+    public int getConstant() {
+        return 105600;
+    }
+
+    @Override
+    public double getWeight() {
+        return 0.02;
+    }
+
+    @Override
+    public int getAdjustment() {
+        return 60000;
+    }
+}

test/InsuranceCalculatorTest.java

@@ -0,0 +1,30 @@
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class InsuranceCalculatorTest {
+    @Test
+    public void lowIncome() {
+        assertEquals(1825, insuranceFor(5000), 0.01);
+    }
+
+    @Test
+    public void mediumIncome() {
+        assertEquals(38600, insuranceFor(25000), 0.01);
+    }
+
+    @Test
+    public void highIncome() {
+        assertEquals(78500, insuranceFor(50000), 0.01);
+    }
+
+    @Test
+    public void veryHighIncome() {
+        assertEquals(106400, insuranceFor(100000), 0.01);
+    }
+
+    private double insuranceFor(double income) {
+        return new InsuranceCalculator().calculateInsurance(income);
+    }
+
+}