diff --git a/FirebaseVertexAI/Tests/Unit/GenerativeModelTests.swift b/FirebaseVertexAI/Tests/Unit/GenerativeModelTests.swift
index ac1980d93d4..13c625036cc 100644
--- a/FirebaseVertexAI/Tests/Unit/GenerativeModelTests.swift
+++ b/FirebaseVertexAI/Tests/Unit/GenerativeModelTests.swift
@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+import FirebaseAppCheckInterop
 import XCTest
 
 @testable import FirebaseVertexAI
@@ -178,6 +179,43 @@ final class GenerativeModelTests: XCTestCase {
     _ = try await model.generateContent(testPrompt)
   }
 
+  func testGenerateContent_appCheck_validToken() async throws {
+    let appCheckToken = "test-valid-token"
+    model = GenerativeModel(
+      name: "my-model",
+      apiKey: "API_KEY",
+      requestOptions: RequestOptions(),
+      appCheck: AppCheckInteropFake(token: appCheckToken),
+      urlSession: urlSession
+    )
+    MockURLProtocol
+      .requestHandler = try httpRequestHandler(
+        forResource: "unary-success-basic-reply-short",
+        withExtension: "json",
+        appCheckToken: appCheckToken
+      )
+
+    _ = try await model.generateContent(testPrompt)
+  }
+
+  func testGenerateContent_appCheck_tokenRefreshError() async throws {
+    model = GenerativeModel(
+      name: "my-model",
+      apiKey: "API_KEY",
+      requestOptions: RequestOptions(),
+      appCheck: AppCheckInteropFake(error: AppCheckErrorFake()),
+      urlSession: urlSession
+    )
+    MockURLProtocol
+      .requestHandler = try httpRequestHandler(
+        forResource: "unary-success-basic-reply-short",
+        withExtension: "json",
+        appCheckToken: AppCheckInteropFake.placeholderTokenValue
+      )
+
+    _ = try await model.generateContent(testPrompt)
+  }
+
   func testGenerateContent_failure_invalidAPIKey() async throws {
     let expectedStatusCode = 400
     MockURLProtocol
@@ -654,6 +692,45 @@ final class GenerativeModelTests: XCTestCase {
       .contains(where: { $0.startIndex == 899 && $0.endIndex == 1026 && !$0.uri.isEmpty }))
   }
 
+  func testGenerateContentStream_appCheck_validToken() async throws {
+    let appCheckToken = "test-valid-token"
+    model = GenerativeModel(
+      name: "my-model",
+      apiKey: "API_KEY",
+      requestOptions: RequestOptions(),
+      appCheck: AppCheckInteropFake(token: appCheckToken),
+      urlSession: urlSession
+    )
+    MockURLProtocol
+      .requestHandler = try httpRequestHandler(
+        forResource: "streaming-success-basic-reply-short",
+        withExtension: "txt",
+        appCheckToken: appCheckToken
+      )
+
+    let stream = model.generateContentStream(testPrompt)
+    for try await _ in stream {}
+  }
+
+  func testGenerateContentStream_appCheck_tokenRefreshError() async throws {
+    model = GenerativeModel(
+      name: "my-model",
+      apiKey: "API_KEY",
+      requestOptions: RequestOptions(),
+      appCheck: AppCheckInteropFake(error: AppCheckErrorFake()),
+      urlSession: urlSession
+    )
+    MockURLProtocol
+      .requestHandler = try httpRequestHandler(
+        forResource: "streaming-success-basic-reply-short",
+        withExtension: "txt",
+        appCheckToken: AppCheckInteropFake.placeholderTokenValue
+      )
+
+    let stream = model.generateContentStream(testPrompt)
+    for try await _ in stream {}
+  }
+
   func testGenerateContentStream_errorMidStream() async throws {
     MockURLProtocol.requestHandler = try httpRequestHandler(
       forResource: "streaming-failure-error-mid-stream",
@@ -887,8 +964,8 @@ final class GenerativeModelTests: XCTestCase {
   private func httpRequestHandler(forResource name: String,
                                   withExtension ext: String,
                                   statusCode: Int = 200,
-                                  timeout: TimeInterval = URLRequest
-                                    .defaultTimeoutInterval()) throws -> ((URLRequest) throws -> (
+                                  timeout: TimeInterval = URLRequest.defaultTimeoutInterval(),
+                                  appCheckToken: String? = nil) throws -> ((URLRequest) throws -> (
     URLResponse,
     AsyncLineSequence<URL.AsyncBytes>?
   )) {
@@ -897,6 +974,7 @@ final class GenerativeModelTests: XCTestCase {
       let requestURL = try XCTUnwrap(request.url)
       XCTAssertEqual(requestURL.path.occurrenceCount(of: "models/"), 1)
       XCTAssertEqual(request.timeoutInterval, timeout)
+      XCTAssertEqual(request.value(forHTTPHeaderField: "X-Firebase-AppCheck"), appCheckToken)
       let response = try XCTUnwrap(HTTPURLResponse(
         url: requestURL,
         statusCode: statusCode,
@@ -922,3 +1000,52 @@ private extension URLRequest {
     return URLRequest(url: placeholderURL).timeoutInterval
   }
 }
+
+class AppCheckInteropFake: NSObject, AppCheckInterop {
+  /// The placeholder token value returned when an error occurs
+  static let placeholderTokenValue = "placeholder-token"
+
+  var token: String
+  var error: Error?
+
+  private init(token: String, error: Error?) {
+    self.token = token
+    self.error = error
+  }
+
+  convenience init(token: String) {
+    self.init(token: token, error: nil)
+  }
+
+  convenience init(error: Error) {
+    self.init(token: AppCheckInteropFake.placeholderTokenValue, error: error)
+  }
+
+  func getToken(forcingRefresh: Bool) async -> any FIRAppCheckTokenResultInterop {
+    return AppCheckTokenResultInteropFake(token: token, error: error)
+  }
+
+  func tokenDidChangeNotificationName() -> String {
+    fatalError("\(#function) not implemented.")
+  }
+
+  func notificationTokenKey() -> String {
+    fatalError("\(#function) not implemented.")
+  }
+
+  func notificationAppNameKey() -> String {
+    fatalError("\(#function) not implemented.")
+  }
+
+  private class AppCheckTokenResultInteropFake: NSObject, FIRAppCheckTokenResultInterop {
+    var token: String
+    var error: Error?
+
+    init(token: String, error: Error?) {
+      self.token = token
+      self.error = error
+    }
+  }
+}
+
+struct AppCheckErrorFake: Error {}