Add Unit test to confirm domain error carries through the boxed type

Author: aashishpatil-g

Tests/Unit/ErrorsTypes.swift

@@ -0,0 +1,67 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import Foundation
+import Combine
+import XCTest
+
+import FirebaseCore
+@testable import FirebaseDataConnect
+
+@available(iOS 15.0, macOS 12.0, tvOS 15.0, watchOS 8.0, *)
+final class ErrorTypesTests: XCTestCase {
+
+  private var pubCancellable: AnyCancellable?
+  private let errPublisher = PassthroughSubject<Result<String, AnyDataConnectError>, Never>()
+
+  func throwInitError() throws  {
+    throw DataConnectInitError.appNotConfigured()
+  }
+
+  func testCatchAsGenericTypes() throws {
+    do {
+      try throwInitError()
+    } catch let dcerr as DataConnectError {
+      XCTAssertTrue(true)
+    }
+  }
+
+  func testPublisherErrorType() throws {
+
+    let errExpectation = XCTestExpectation(description: "Expect a Domain Erro")
+
+    pubCancellable = errPublisher.sink( receiveValue: { result in
+      switch result {
+      case .success(_):
+        XCTFail("Unexpectedly got success. We expect a failure with error")
+      case let .failure(dcerror):
+        if let initErr = dcerror.dataConnectError as? DataConnectInitError,
+           initErr.code == .appNotConfigured
+        {
+          // got Init domain error
+          errExpectation.fulfill()
+        } else {
+          XCTFail("Did not get DataConnectInitError.appNotConfigured as expected")
+        }
+      }
+    })
+
+    errPublisher
+      .send(
+        .failure(AnyDataConnectError(dataConnectError: DataConnectInitError.appNotConfigured()))
+      )
+
+    wait(for: [errExpectation], timeout: 1.0)
+  }
+}