diff --git a/Package.resolved b/Package.resolved
index 1c03815..1c3ea92 100644
--- a/Package.resolved
+++ b/Package.resolved
@@ -6,8 +6,8 @@
         "repositoryURL": "https://github.com/openid/AppAuth-iOS",
         "state": {
           "branch": null,
-          "revision": "01131d68346c8ae552961c768d583c715fbe1410",
-          "version": "1.4.0"
+          "revision": "3d36a58a2b736f7bc499453e996a704929b25080",
+          "version": "1.6.0"
         }
       },
       {
diff --git a/Package.swift b/Package.swift
index 8cd9bae..4851df9 100644
--- a/Package.swift
+++ b/Package.swift
@@ -13,7 +13,7 @@ let package = Package(
             targets: ["TIM"]),
     ],
     dependencies: [
-        .package(name: "AppAuth", url: "https://github.com/openid/AppAuth-iOS", .exact("1.4.0")),
+        .package(name: "AppAuth", url: "https://github.com/openid/AppAuth-iOS", .exact("1.6.0")),
         .package(name: "TIMEncryptedStorage", url: "https://github.com/trifork/TIMEncryptedStorage-iOS", .exact("2.2.1")),
 
     ],
diff --git a/Sources/TIM/AppAuth/AppAuthController.swift b/Sources/TIM/AppAuth/AppAuthController.swift
index 1b2b667..94cd136 100644
--- a/Sources/TIM/AppAuth/AppAuthController.swift
+++ b/Sources/TIM/AppAuth/AppAuthController.swift
@@ -1,4 +1,3 @@
-import UIKit
 import AppAuth
 import SafariServices
 
@@ -177,7 +176,7 @@ public final class AppAuthController: OpenIDConnectController {
 
     public func accessToken(forceRefresh: Bool, _ completion: @escaping (Result<JWT, TIMAuthError>) -> Void) {
         guard let authState = self.authState else {
-            completion(.failure(TIMAuthError.authStateNil))
+            completion(.failure(TIMAuthError.authStateNil()))
             return
         }
         if forceRefresh {
diff --git a/Sources/TIM/Models/Errors.swift b/Sources/TIM/Models/Errors.swift
deleted file mode 100644
index a2e183a..0000000
--- a/Sources/TIM/Models/Errors.swift
+++ /dev/null
@@ -1,159 +0,0 @@
-import Foundation
-import AppAuth
-import TIMEncryptedStorage
-
-/// Shared wrapper for Auth and Storage errors.
-public enum TIMError: Error, LocalizedError {
-    case auth(TIMAuthError)
-    case storage(TIMStorageError)
-
-    public var errorDescription: String? {
-        switch self {
-        case .auth(let error):
-            return error.localizedDescription
-        case .storage(let error):
-            return error.localizedDescription
-        }
-    }
-}
-
-/// Errors related to AppAuth operations
-public enum TIMAuthError: Error, LocalizedError {
-    case authStateNil
-    case failedToDiscoverConfiguration
-    case failedToBeginAuth
-    case failedToGetAccessToken
-    case failedToGetRefreshToken
-    case networkError
-    case refreshTokenExpired
-    case appAuthFailed(Error?)
-    case safariViewControllerCancelled
-    case failedToGetRequiredDataInToken
-    case failedToValidateIDToken
-
-    public var errorDescription: String? {
-        switch self {
-        case .authStateNil:
-            return "The AuthState was nil, when it wasn't expected to be. Are you trying to get the access token, when there was no valid session?"
-        case .failedToDiscoverConfiguration:
-            return "Failed to discover the configuration on the server. Check your configuration setup and try again."
-        case .failedToBeginAuth:
-            return "AppAuth returned a weird state, while we tried to begin the authentication."
-        case .failedToGetAccessToken:
-            return "Failed to get the access token."
-        case .failedToGetRefreshToken:
-            return "Failed to get the refresh token."
-        case .networkError:
-            return "Network error caused by AppAuth"
-        case .refreshTokenExpired:
-            return "The refresh token has expired."
-        case .appAuthFailed(let error):
-            return "Something went wrong in the AppAuth framework: \(error?.localizedDescription ?? "nil")"
-        case .safariViewControllerCancelled:
-            return "The user cancelled OpenID connect login via SafariViewController"
-        case .failedToGetRequiredDataInToken:
-            return "TIM did not find the required data (userId) in the token. The 'sub' property must be present in the token!"
-        case .failedToValidateIDToken:
-            return "AppAuth failed to validate the ID Token. This will happen if the client's time is more than 10 minutes off the current time."
-        }
-    }
-
-    static func mapAppAuthError(_ error: Error?) -> TIMAuthError {
-        guard let error = error as NSError? else {
-            return .appAuthFailed(nil)
-        }
-
-        if error.domain == OIDGeneralErrorDomain {
-            switch error.code {
-            case OIDErrorCode.networkError.rawValue: return .networkError
-            case OIDErrorCode.idTokenFailedValidationError.rawValue: return .failedToValidateIDToken
-            default: return .appAuthFailed(error)
-            }
-        } else if error.domain == OIDOAuthTokenErrorDomain {
-            switch error.code {
-            case OIDErrorCodeOAuth.invalidGrant.rawValue: return .refreshTokenExpired
-            default: return .appAuthFailed(error)
-            }
-        }
-
-        return .appAuthFailed(error)
-    }
-
-    /// Tells whether the error was a `.safariViewControllerCancelled` or not.
-    public func isSafariViewControllerCancelled() -> Bool {
-        switch self {
-        case .safariViewControllerCancelled:
-            return true
-        default:
-            return false
-        }
-    }
-}
-
-/// Errors related to storage operations
-public enum TIMStorageError: Error, LocalizedError {
-    case encryptedStorageFailed(TIMEncryptedStorageError)
-
-    // This error was implemented because we discovered missing keyIds for some users, where the user was cleared while waiting for response with a new refreshToken
-    case incompleteUserDataSet
-
-    public var errorDescription: String? {
-        switch self {
-        case .encryptedStorageFailed(let error):
-            return "The encrypted storage failed: \(error.localizedDescription)"
-        case .incompleteUserDataSet:
-            return "Attempt to store a refresh token for a user, that does not have a valid data set. This can happen if you clear the user data while waiting for a login (which definitely should be avoided!). The invalid data has now been cleared from the framework. The user will have to perform OIDC login again."
-        }
-    }
-
-    public func isKeyLocked() -> Bool {
-        isKeyServiceError(.keyLocked)
-    }
-
-    public func isWrongPassword() -> Bool {
-        isKeyServiceError(.badPassword)
-    }
-
-    public func isBiometricFailedError() -> Bool {
-        switch self {
-        case .encryptedStorageFailed(let storageError):
-            switch storageError {
-            case .secureStorageFailed(let secureStorageError) where secureStorageError == .authenticationFailedForData:
-                return true
-            default:
-                return false
-            }
-        case .incompleteUserDataSet:
-            return false
-        }
-    }
-
-    /// Determines whether this error is an error thrown by the KeyService.
-    ///
-    /// This might be useful for handling unexpected cases from the encryption part of the framework.
-    /// When the key service fails you don't want to do any drastic fallback, since the server might "just" be down or the user have no internet connection. You will be able to recover later on, from a key service error.
-    public func isKeyServiceError() -> Bool {
-        isKeyServiceError(nil)
-    }
-
-    /// Determines whether this error is a specific kind of key service error.
-    /// - Parameter keyServiceError: The key service error to look for. If `nil` is passed it will look for any kind of key service error.
-    private func isKeyServiceError(_ keyServiceError: TIMKeyServiceError?) -> Bool {
-        let isKeyServiceError: Bool
-        switch self {
-        case .encryptedStorageFailed(let error):
-            if case TIMEncryptedStorageError.keyServiceFailed(let ksError) = error {
-                if let keyServiceError = keyServiceError {
-                    isKeyServiceError = ksError == keyServiceError
-                } else {
-                    isKeyServiceError = true // Is any kind of key service error!
-                }
-            } else {
-                isKeyServiceError = false
-            }
-        case .incompleteUserDataSet:
-            isKeyServiceError = false
-        }
-        return isKeyServiceError
-    }
-}
diff --git a/Sources/TIM/Models/TIMAuthError.swift b/Sources/TIM/Models/TIMAuthError.swift
new file mode 100644
index 0000000..97fe543
--- /dev/null
+++ b/Sources/TIM/Models/TIMAuthError.swift
@@ -0,0 +1,77 @@
+import Foundation
+import AppAuth
+import TIMEncryptedStorage
+
+/// Errors related to AppAuth operations
+public enum TIMAuthError: Error, LocalizedError {
+    //TODO consider renaming this to "missingLogin" or alike which communicates the real issue.
+    case authStateNil(stacktrace: [String] = Thread.callStackSymbols)
+    case failedToDiscoverConfiguration
+    case failedToBeginAuth
+    case failedToGetAccessToken
+    case failedToGetRefreshToken
+    case networkError
+    case refreshTokenExpired
+    case appAuthFailed(Error?)
+    case safariViewControllerCancelled
+    case failedToGetRequiredDataInToken
+    case failedToValidateIDToken
+
+    public var errorDescription: String? {
+        switch self {
+        case .authStateNil(let stacktrace):
+            return "The AuthState was nil, when it wasn't expected to be. Are you trying to get the access token, when there was no valid session? (stacktrace: \(stacktrace))"
+        case .failedToDiscoverConfiguration:
+            return "Failed to discover the configuration on the server. Check your configuration setup and try again."
+        case .failedToBeginAuth:
+            return "AppAuth returned a weird state, while we tried to begin the authentication."
+        case .failedToGetAccessToken:
+            return "Failed to get the access token."
+        case .failedToGetRefreshToken:
+            return "Failed to get the refresh token."
+        case .networkError:
+            return "Network error caused by AppAuth"
+        case .refreshTokenExpired:
+            return "The refresh token has expired."
+        case .appAuthFailed(let error):
+            return "Something went wrong in the AppAuth framework: \(error?.localizedDescription ?? "nil")"
+        case .safariViewControllerCancelled:
+            return "The user cancelled OpenID connect login via SafariViewController"
+        case .failedToGetRequiredDataInToken:
+            return "TIM did not find the required data (userId) in the token. The 'sub' property must be present in the token!"
+        case .failedToValidateIDToken:
+            return "AppAuth failed to validate the ID Token. This will happen if the client's time is more than 10 minutes off the current time."
+        }
+    }
+
+    static func mapAppAuthError(_ error: Error?) -> TIMAuthError {
+        guard let error = error as NSError? else {
+            return .appAuthFailed(nil)
+        }
+        
+        switch error.domain {
+        case OIDGeneralErrorDomain:
+            switch error.code {
+                case OIDErrorCode.networkError.rawValue: return .networkError
+                case OIDErrorCode.idTokenFailedValidationError.rawValue: return .failedToValidateIDToken
+                default: break
+            }
+        case OIDOAuthTokenErrorDomain:
+            switch error.code {
+                case OIDErrorCodeOAuth.invalidGrant.rawValue: return .refreshTokenExpired
+                default: break
+            }
+        default: break
+        }
+        
+        return .appAuthFailed(error)
+    }
+
+    /// Tells whether the error was a `.safariViewControllerCancelled` or not.
+    public func isSafariViewControllerCancelled() -> Bool {
+        if case .safariViewControllerCancelled  = self {
+           return true
+        }
+        return false
+    }
+}
diff --git a/Sources/TIM/Models/TIMStorageError.swift b/Sources/TIM/Models/TIMStorageError.swift
new file mode 100644
index 0000000..7fd5de5
--- /dev/null
+++ b/Sources/TIM/Models/TIMStorageError.swift
@@ -0,0 +1,71 @@
+import Foundation
+import AppAuth
+import TIMEncryptedStorage
+
+/// Errors related to storage operations
+public enum TIMStorageError: Error, LocalizedError {
+    case encryptedStorageFailed(TIMEncryptedStorageError)
+
+    // This error was implemented because we discovered missing keyIds for some users, where the user was cleared while waiting for response with a new refreshToken
+    case incompleteUserDataSet
+
+    public var errorDescription: String? {
+        switch self {
+        case .encryptedStorageFailed(let error):
+            return "The encrypted storage failed: \(error.localizedDescription)"
+        case .incompleteUserDataSet:
+            return "Attempt to store a refresh token for a user, that does not have a valid data set. This can happen if you clear the user data while waiting for a login (which definitely should be avoided!). The invalid data has now been cleared from the framework. The user will have to perform OIDC login again."
+        }
+    }
+
+    public func isKeyLocked() -> Bool {
+        isKeyServiceError(.keyLocked)
+    }
+
+    public func isWrongPassword() -> Bool {
+        isKeyServiceError(.badPassword)
+    }
+
+    public func isBiometricFailedError() -> Bool {
+        switch self {
+        case .encryptedStorageFailed(let storageError):
+            switch storageError {
+            case .secureStorageFailed(let secureStorageError) where secureStorageError == .authenticationFailedForData:
+                return true
+            default:
+                return false
+            }
+        case .incompleteUserDataSet:
+            return false
+        }
+    }
+
+    /// Determines whether this error is an error thrown by the KeyService.
+    ///
+    /// This might be useful for handling unexpected cases from the encryption part of the framework.
+    /// When the key service fails you don't want to do any drastic fallback, since the server might "just" be down or the user have no internet connection. You will be able to recover later on, from a key service error.
+    public func isKeyServiceError() -> Bool {
+        isKeyServiceError(nil)
+    }
+
+    /// Determines whether this error is a specific kind of key service error.
+    /// - Parameter keyServiceError: The key service error to look for. If `nil` is passed it will look for any kind of key service error.
+    private func isKeyServiceError(_ keyServiceError: TIMKeyServiceError?) -> Bool {
+        let isKeyServiceError: Bool
+        switch self {
+        case .encryptedStorageFailed(let error):
+            if case TIMEncryptedStorageError.keyServiceFailed(let ksError) = error {
+                if let keyServiceError = keyServiceError {
+                    isKeyServiceError = ksError == keyServiceError
+                } else {
+                    isKeyServiceError = true // Is any kind of key service error!
+                }
+            } else {
+                isKeyServiceError = false
+            }
+        case .incompleteUserDataSet:
+            isKeyServiceError = false
+        }
+        return isKeyServiceError
+    }
+}
diff --git a/Sources/TIM/Models/TimError.swift b/Sources/TIM/Models/TimError.swift
new file mode 100644
index 0000000..d7dd338
--- /dev/null
+++ b/Sources/TIM/Models/TimError.swift
@@ -0,0 +1,18 @@
+import Foundation
+import AppAuth
+import TIMEncryptedStorage
+
+/// Shared wrapper for Auth and Storage errors.
+public enum TIMError: Error, LocalizedError {
+    case auth(TIMAuthError)
+    case storage(TIMStorageError)
+
+    public var errorDescription: String? {
+        switch self {
+        case .auth(let error):
+            return error.localizedDescription
+        case .storage(let error):
+            return error.localizedDescription
+        }
+    }
+}
diff --git a/Tests/TIMTests/TIMAuthErrorTests.swift b/Tests/TIMTests/TIMAuthErrorTests.swift
new file mode 100644
index 0000000..b7e04ae
--- /dev/null
+++ b/Tests/TIMTests/TIMAuthErrorTests.swift
@@ -0,0 +1,112 @@
+import XCTest
+import AppAuth
+@testable import TIM
+
+final class TimErrorTests: XCTestCase {
+    
+    func testIsSafariViewControllerCancelled(){
+        XCTAssertFalse(TIMAuthError.failedToBeginAuth.isSafariViewControllerCancelled())
+        XCTAssertFalse(TIMAuthError.appAuthFailed(nil).isSafariViewControllerCancelled())
+        XCTAssertFalse(TIMAuthError.authStateNil().isSafariViewControllerCancelled())
+        XCTAssertFalse(TIMAuthError.failedToValidateIDToken.isSafariViewControllerCancelled())
+        XCTAssertFalse(TIMAuthError.refreshTokenExpired.isSafariViewControllerCancelled())
+        
+        XCTAssertTrue(TIMAuthError.safariViewControllerCancelled.isSafariViewControllerCancelled())
+    }
+    
+    func testMapAppAuthErrorNil(){
+        let error = TIMAuthError.mapAppAuthError(nil)
+        error.assertAppAuthFailed(expectedError: nil)
+    }
+    
+    func testMapAppAuthErrorRegularNSError(){
+        let innerAuthError = NSError(domain: "someDomain", code: 42)
+        let error = TIMAuthError.mapAppAuthError(innerAuthError)
+        error.assertAppAuthFailed(expectedError: innerAuthError)
+    }
+    
+    func testMapAppAuthErrorOIDGeneralErrorDomainNetworkError() {
+        let innerAuthError = NSError(
+            domain: OIDGeneralErrorDomain,
+            code: OIDErrorCode.networkError.rawValue
+        )
+        
+        let error = TIMAuthError.mapAppAuthError(innerAuthError)
+        error.assertNetworkError()
+    }
+    
+    func testMapAppAuthErrorOIDGeneralErrorDomainIdTokenError() {
+        let innerAuthError = NSError(
+            domain: OIDGeneralErrorDomain,
+            code: OIDErrorCode.idTokenFailedValidationError.rawValue
+        )
+        
+        let error = TIMAuthError.mapAppAuthError(innerAuthError)
+        error.assertFailedToValidateIDToken()
+    }
+    
+    func testMapAppAuthErrorOIDGeneralErrorDomainUnknownErrorType(){
+        let innerAuthError = NSError(
+            domain: OIDGeneralErrorDomain,
+            code: 999
+        )
+        
+        let error = TIMAuthError.mapAppAuthError(innerAuthError)
+        error.assertAppAuthFailed(expectedError: innerAuthError)
+    }
+    
+    func testMapAppAuthErrorOIDOAuthTokenErrorDomainInvalidGrant(){
+        let innerAuthError = NSError(
+            domain: OIDOAuthTokenErrorDomain,
+            code: OIDErrorCodeOAuth.invalidGrant.rawValue
+        )
+        
+        let error = TIMAuthError.mapAppAuthError(innerAuthError)
+        error.assertRefreshTokenExpired()
+    }
+
+    func testMapAppAuthErrorOIDOAuthTokenErrorDomainUnknownErrorType(){
+        let innerAuthError = NSError(
+            domain: OIDOAuthTokenErrorDomain,
+            code: 999
+        )
+        
+        let error = TIMAuthError.mapAppAuthError(innerAuthError)
+        error.assertAppAuthFailed(expectedError: innerAuthError)
+    }
+    
+}
+
+extension TIMAuthError {
+    func assertAppAuthFailed(expectedError: NSError?){
+        if case TIMAuthError.appAuthFailed(let appAuthError) = self  {
+            XCTAssertEqual(expectedError, appAuthError as? NSError)
+        } else {
+            XCTFailTest(message: "Expected an appAuthFailed but got \(self)")
+        }
+    }
+    
+    func assertNetworkError(){
+        if case TIMAuthError.networkError = self  {
+            
+        } else {
+            XCTFailTest(message: "Expected a networkError but got \(self)")
+        }
+    }
+
+    func assertFailedToValidateIDToken(){
+        if case TIMAuthError.failedToValidateIDToken = self  {
+            
+        } else {
+            XCTFailTest(message: "Expected a failedToValidateIDToken but got \(self)")
+        }
+    }
+    
+    func assertRefreshTokenExpired(){
+        if case TIMAuthError.refreshTokenExpired = self  {
+            
+        } else {
+            XCTFailTest(message: "Expected a refreshTokenExpired but got \(self)")
+        }
+    }
+}
diff --git a/Tests/TIMTests/TestHelpers.swift b/Tests/TIMTests/TestHelpers.swift
new file mode 100644
index 0000000..be488ab
--- /dev/null
+++ b/Tests/TIMTests/TestHelpers.swift
@@ -0,0 +1,10 @@
+import XCTest
+import Foundation
+
+func XCTFailTest(
+    message: String = "Should not have been called",
+    file: StaticString = #filePath,
+    line: UInt = #line
+){
+    XCTAssertTrue(false, message, file: file, line: line)
+}