tuispec

Playwright-like black-box testing for terminal UIs over PTY.

tuispec is a Haskell library that lets you write reliable TUI tests as normal Haskell programs. Interact with any terminal application via PTY — send keystrokes, wait for text, and capture snapshots — without instrumenting the target app.

Example output

Snapshots captured from the included Brick demo app using tuispec:

Features

• PTY transport — tests interact with real terminal apps over PTY
• Per-test isolation — fresh PTY process per test, no shared state
• Snapshot assertions — baseline comparison with ANSI text + PNG artifacts
• Text selectors — Exact, Regex, At, Within, Nth
• tasty integration — tests are regular tasty test trees
• JSON-RPC server — agentic orchestration of TUIs via tuispec server
• REPL sessions — ad-hoc exploration with withTuiSession

Quick start

Add tuispec to your build-depends and write a test:

{-# LANGUAGE OverloadedStrings #-}

import Test.Tasty (defaultMain, testGroup)
import TuiSpec

main :: IO ()
main =
  defaultMain $ testGroup "demo"
    [ tuiTest defaultRunOptions "counter" $ \tui -> do
        launch tui (App "my-tui" [])
        waitForText tui (Exact "Ready")
        press tui (CharKey '+')
        expectSnapshot tui "counter-updated"
        press tui (CharKey 'q')
    ]

Run:

cabal test

Building from source

cabal build

Run root smoke tests:

cabal test

Run the Brick demo integration suite:

cd example
cabal test

DSL overview

Actions

launch    :: Tui -> App -> IO ()
press     :: Tui -> Key -> IO ()
pressCombo :: Tui -> [Modifier] -> Key -> IO ()
typeText  :: Tui -> Text -> IO ()
sendLine  :: Tui -> Text -> IO ()

Waits and assertions

waitForText    :: Tui -> Selector -> IO ()
expectVisible  :: Tui -> Selector -> IO ()
expectNotVisible :: Tui -> Selector -> IO ()
expectSnapshot :: Tui -> SnapshotName -> IO ()
dumpView       :: Tui -> SnapshotName -> IO FilePath

Selectors

Exact  Text           -- exact substring match
Regex  Text           -- lightweight regex (|, .*, literal parens stripped)
At     Int Int        -- position-based (col, row)
Within Rect Selector  -- restrict to a rectangle
Nth    Int Selector   -- pick the Nth match

Keys

Named keys: Enter, Esc, Tab, Backspace, arrows, FunctionKey 1..12

Character keys: CharKey c, Ctrl c, AltKey c

Combos: pressCombo [Control] (CharKey 'c')

Snapshots

For a test named my test (slug: my-test) with artifactsDir = "artifacts":

• Baselines: artifacts/snapshots/my-test/<snapshot>.ansi.txt
• Per-run: artifacts/tests/my-test/snapshots/<snapshot>.ansi.txt

Render any ANSI snapshot to PNG:

cabal run tuispec -- render artifacts/tests/my-test/snapshots/<snapshot>.ansi.txt

Specify an explicit font file:

cabal run tuispec -- render --font /path/to/YourMono.ttf artifacts/tests/my-test/snapshots/<snapshot>.ansi.txt

Render visible plain text:

cabal run tuispec -- render-text artifacts/tests/my-test/snapshots/<snapshot>.ansi.txt

JSON-RPC server

cabal run tuispec -- server --artifact-dir artifacts/server

Newline-delimited JSON-RPC 2.0 on stdin/stdout for agentic orchestration of TUIs. See SERVER.md for the full protocol reference.

Ping example:

printf '%s\n' \
  '{"jsonrpc":"2.0","id":1,"method":"server.ping","params":{}}' \
  | cabal run tuispec -- server --artifact-dir artifacts/server

End-to-end session example:

cat <<'JSON' | cabal run tuispec -- server --artifact-dir artifacts/server
{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"name":"rpc-demo","terminalCols":134,"terminalRows":40}}
{"jsonrpc":"2.0","id":2,"method":"launch","params":{"command":"sh","args":[]}}
{"jsonrpc":"2.0","id":3,"method":"sendLine","params":{"text":"printf 'hello from rpc\\n'"}}
{"jsonrpc":"2.0","id":4,"method":"waitForText","params":{"selector":{"type":"exact","text":"hello from rpc"}}}
{"jsonrpc":"2.0","id":5,"method":"dumpView","params":{"name":"after-hello"}}
{"jsonrpc":"2.0","id":6,"method":"server.shutdown","params":{}}
JSON

Input examples:

{"jsonrpc":"2.0","id":7,"method":"sendKey","params":{"key":"+"}}
{"jsonrpc":"2.0","id":8,"method":"sendKey","params":{"key":"Ctrl+C"}}
{"jsonrpc":"2.0","id":9,"method":"sendText","params":{"text":"hello"}}

REPL-style sessions

For ad-hoc exploration outside tasty:

withTuiSession defaultRunOptions "demo" $ \tui -> do
  launch tui (App "sh" [])
  sendLine tui "echo hello"
  _ <- dumpView tui "step-1"
  pure ()

Configuration

RunOptions fields (all overridable via environment variables):

Field	Default	Env var
timeoutSeconds	5	TUISPEC_TIMEOUT_SECONDS
retries	0	TUISPEC_RETRIES
stepRetries	0	TUISPEC_STEP_RETRIES
terminalCols	134	TUISPEC_TERMINAL_COLS
terminalRows	40	TUISPEC_TERMINAL_ROWS
artifactsDir	"artifacts"	TUISPEC_ARTIFACTS_DIR
updateSnapshots	False	TUISPEC_UPDATE_SNAPSHOTS
ambiguityMode	FailOnAmbiguous	TUISPEC_AMBIGUITY_MODE
snapshotTheme	"auto"	TUISPEC_SNAPSHOT_THEME

Requirements

• GHC 9.12+
• Linux terminal environment (PTY-based)
• python3 with Pillow for PNG rendering
• a host monospace TTF/TTC font (or pass --font, or TUISPEC_FONT_PATH)

License

MIT — Matthias Pall Gissurarson