lsp-test: Functional test framework for LSP servers.

[ bsd3, library, testing ] [ Propose Tags ]

A test framework for writing tests against Language Server Protocol servers. Language.Haskell.LSP.Test launches your server as a subprocess and allows you to simulate a session down to the wire, and Language.Haskell.LSP.Test can replay captured sessions from It's currently used for testing in haskell-ide-engine.

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Dependencies aeson, aeson-pretty, ansi-terminal, base (>=4.7 && <5), bytestring, conduit, conduit-parse, containers, data-default, Diff, directory, filepath, haskell-lsp (==0.8.*), lens, mtl, parser-combinators, process, text, transformers, unix, unordered-containers, Win32, yi-rope [details]
License BSD-3-Clause
Copyright 2018 Luke Lau
Author Luke Lau
Category Testing
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Source repo head: git clone
Uploaded by luke_ at Tue Nov 13 20:37:17 UTC 2018
Distributions LTSHaskell:, NixOS:, Stackage:
Downloads 564 total (123 in the last 30 days)
Rating 2.0 (votes: 1) [estimated by rule of succession]
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Status Hackage Matrix CI
Docs available [build log]
Last success reported on 2018-11-13 [all 1 reports]


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lsp-test Build Status Hackage

lsp-test is a functional testing framework for Language Server Protocol servers.

import Language.Haskell.LSP.Test
runSession "hie" fullCaps "proj/dir" $ do
  doc <- openDoc "Foo.hs" "haskell"
  skipMany anyNotification
  symbols <- getDocumentSymbols doc


Unit tests with HSpec

describe "diagnostics" $
  it "report errors" $ runSession "hie" fullCaps "test/data" $ do
    openDoc "Error.hs" "haskell"
    [diag] <- waitForDiagnosticsSource "ghcmod"
    liftIO $ do
      diag ^. severity `shouldBe` Just DsError
      diag ^. source `shouldBe` Just "ghcmod"

Replaying captured session

replaySession "hie" "test/data/renamePass"

Parsing with combinators

skipManyTill loggingNotification publishDiagnosticsNotification
count 4 (message :: Session ApplyWorkspaceEditRequest)
anyRequest <|> anyResponse

Try out the example tests in the example directory with cabal new-test. For more examples check the Wiki


To test make sure you have the following language servers installed: