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diff --git a/tests/BTLS/Assertions.hs b/tests/BTLS/Assertions.hs
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+-- Copyright 2018 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
+--
+--     https://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.
+
+module BTLS.Assertions
+  ( isRightAndHolds
+  ) where
+
+import Control.Monad (unless)
+import Test.Tasty.HUnit (Assertion, assertFailure)
+
+isRightAndHolds :: (Eq a, Show a, Show e) => Either e a -> a -> Assertion
+actual@(Left _) `isRightAndHolds` _ =
+  assertFailure ("expected: Right _\n but got: " ++ show actual)
+Right actual `isRightAndHolds` expected =
+  unless (expected == actual) $
+    assertFailure ("expected: Right " ++ show expected ++ "\n but got: Right " ++ show actual)