update fake and create test

Author: camden-king

GoogleSignIn/Sources/GIDAuthStateMigration/Fake/GIDFakeAuthStateMigration.h

@@ -14,9 +14,14 @@
  * limitations under the License.
  */
 
-#import "GoogleSignIn/Sources/GIDAuthStateMigration.h"
+#import "GoogleSignIn/Sources/GIDAuthStateMigration/GIDAuthStateMigration.h"
 
 /// A fake |GIDAuthStateMigration| for testing.
 @interface GIDFakeAuthStateMigration : GIDAuthStateMigration
 
+/// Callback that is called when `migrateIfNeededWithTokenURL` is invoked.
+@property (nonatomic, nullable) void (^migrationInvokedCallback)
+  (NSURL * _Nullable tokenURL, NSString * _Nullable callbackPath, NSString * _Nullable keychainName,
+   BOOL isFreshInstall);
+
 @end

GoogleSignIn/Sources/GIDAuthStateMigration/Fake/GIDFakeAuthStateMigration.m

@@ -13,13 +13,15 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#import "GoogleSignIn/Tests/Unit/GIDFakeAuthStateMigration.h"
+#import "GoogleSignIn/Sources/GIDAuthStateMigration/Fake/GIDFakeAuthStateMigration.h"
 
 
 NS_ASSUME_NONNULL_BEGIN
 
 @implementation GIDFakeAuthStateMigration
 
+@synthesize migrationInvokedCallback = _migrationInvokedCallback;
+
 - (instancetype)initWithKeychainStore:(GTMKeychainStore *)keychainStore {
   self = [super initWithKeychainStore:keychainStore];
   return self;
@@ -33,6 +35,9 @@ - (void)migrateIfNeededWithTokenURL:(NSURL *)tokenURL
                        callbackPath:(NSString *)callbackPath
                        keychainName:(NSString *)keychainName
                      isFreshInstall:(BOOL)isFreshInstall {
+  if (_migrationInvokedCallback) {
+    _migrationInvokedCallback(tokenURL, callbackPath, keychainName, isFreshInstall);
+  }
   return;
 }