test(auth): cover AuthMethodPickerState routing to the MFA, conflict and error handlers

Author: demolaf

FirebaseSwiftUI/FirebaseAuthSwiftUI/Tests/FirebaseAuthSwiftUITests/AuthMethodPickerStateTests.swift

@@ -0,0 +1,100 @@
+// Copyright 2025 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 FirebaseAuth
+@testable import FirebaseAuthSwiftUI
+import Foundation
+import Testing
+
+/// Records which handler `AuthMethodPickerState.route` called.
+@MainActor
+private final class RouteRecorder {
+  var mfa: MFARequired?
+  var conflict: AccountConflictContext?
+  var error: Error?
+
+  func route(_ result: Result<SignInOutcome?, Error>, handlesConflicts: Bool = true) {
+    AuthMethodPickerState.route(
+      result,
+      mfaHandler: { self.mfa = $0 },
+      accountConflictHandler: handlesConflicts ? { self.conflict = $0 } : nil,
+      reportError: { self.error = $0 }
+    )
+  }
+}
+
+private struct TestError: Error {}
+
+private func conflictContext() -> AccountConflictContext {
+  AccountConflictContext(
+    conflictType: .accountExistsWithDifferentCredential,
+    credential: EmailAuthProvider.credential(withEmail: "test@example.com", password: "123456"),
+    underlyingError: TestError(),
+    message: "conflict",
+    email: "test@example.com"
+  )
+}
+
+@Suite("AuthMethodPickerState routing")
+@MainActor
+struct AuthMethodPickerStateRoutingTests {
+  @Test("MFA required goes to the MFA handler")
+  func mfaRequired() {
+    let recorder = RouteRecorder()
+    let mfa = MFARequired(hints: [.totp(displayName: nil, uid: "uid")])
+    recorder.route(.success(.mfaRequired(mfa)))
+    #expect(recorder.mfa == mfa)
+    #expect(recorder.conflict == nil)
+    #expect(recorder.error == nil)
+  }
+
+  @Test("A completed sign-in calls no handler")
+  func signedIn() {
+    let recorder = RouteRecorder()
+    recorder.route(.success(.signedIn(nil)))
+    recorder.route(.success(nil))
+    #expect(recorder.mfa == nil)
+    #expect(recorder.conflict == nil)
+    #expect(recorder.error == nil)
+  }
+
+  @Test("An account conflict goes to the conflict handler")
+  func accountConflict() {
+    let recorder = RouteRecorder()
+    let context = conflictContext()
+    recorder.route(.failure(AuthServiceError.accountConflict(context)))
+    #expect(recorder.conflict == context)
+    #expect(recorder.error == nil)
+  }
+
+  @Test("An account conflict is reported when there is no conflict handler")
+  func accountConflictWithoutHandler() {
+    let recorder = RouteRecorder()
+    recorder.route(
+      .failure(AuthServiceError.accountConflict(conflictContext())),
+      handlesConflicts: false
+    )
+    #expect(recorder.conflict == nil)
+    #expect(recorder.error != nil)
+  }
+
+  @Test("Other errors are reported")
+  func otherError() {
+    let recorder = RouteRecorder()
+    recorder.route(.failure(TestError()))
+    #expect(recorder.error is TestError)
+    #expect(recorder.mfa == nil)
+    #expect(recorder.conflict == nil)
+  }
+}