Add unit test for CouponAllowedEmailsViewModel when the allowed email list is empty

Author: itsmeichigo

WooCommerce/WooCommerceTests/ViewRelated/Coupons/CouponAllowedEmailsViewModelTests.swift

@@ -20,6 +20,23 @@ final class CouponAllowedEmailsViewModelTests: XCTestCase {
         XCTAssertNil(viewModel.notice)
     }
 
+    func test_completion_block_is_triggered_when_allowed_email_list_is_empty() {
+        // Given
+        var savedAddresses: String?
+        let completionBlock: (String) -> Void = { email in
+            savedAddresses = email
+        }
+        let viewModel = CouponAllowedEmailsViewModel(allowedEmails: "[email protected]", onCompletion: completionBlock)
+
+        // When
+        viewModel.emailPatterns = ""
+        viewModel.validateEmails {}
+
+        // Then
+        XCTAssertEqual(savedAddresses, "")
+        XCTAssertNil(viewModel.notice)
+    }
+
     func test_completion_block_is_not_triggered_and_notice_is_not_nil_when_address_validation_fails() {
         var savedAddresses: String?
         let completionBlock: (String) -> Void = { email in