adds validateBusinessOwners method

adds BusinessCheckingAccount Tests

Author: TatsuyaRyujin

lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/BusinessCheckingAccount.java

@@ -17,6 +17,20 @@ public BusinessCheckingAccount(
     super(accountNumber, owners, initialBalance);
   }
 
+  /**
+   * Checks if at least one owner is a business.
+   *
+   * @param owners The owers of the account.
+   * @throws IllegalArgumentEception If no business owner is found.
+   */
+  private void validateBusinessOwner(Set<Customer> owners) {
+    boolean hasBusinessOwner = owners.stream().anyMatch(Customer::isBusiness);
+    if (!hasBusinessOwner) {
+      throw new IllegalArgumentException(
+          "Business Checking Account must have at least one business owner");
+    }
+  }
+
   @Override
   public String toString() {
     return "BusinessCheckingAccount{"

lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/Customer.java

@@ -60,6 +60,15 @@ public Set<Account> getAccounts() {
     return accounts;
   }
 
+  /**
+   * Checks if the owner is a business.
+   *
+   * @return True if the customer is a business, false otherwise.
+   */
+  public boolean isBusiness() {
+    return this.type == CustomerType.BUSINESS;
+  }
+
   @Override
   public int hashCode() {
     return id.hashCode();

lesson_17/bank/bank_app/src/test/java/com/codedifferently/lesson17/bank/BusinessCheckingAccountTest.java

@@ -0,0 +1,22 @@
+package com.codedifferently.lesson17.bank;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.HashSet;
+import java.util.Set;
+import java.util.UUID;
+
+import org.junit.jupiter.api.Test;
+
+public class BusinessCheckingAccountTest {
+
+  @Test
+  void validateBusinessOwner_withBusinessOwner() {
+    Set<Customer> owners = new HashSet<>();
+    owners.add(new Customer(UUID.randomUUID(), "Elon Musk", CustomerType.BUSINESS));
+    owners.add(new Customer(UUID.randomUUID(), "Elon Musk", CustomerType.BUSINESS));
+
+    BusinessCheckingAccount account = new BusinessCheckingAccount("123456789", owners, 1000.0);
+    assertThat(account).isNotNull();
+  }
+}