# testty
Rust-native TUI end-to-end testing framework. Drives a real TUI binary in a
pseudo-terminal, captures location-aware terminal state with `vt100`, and
provides a semantic assertion API for text, style, color, and region checks.
Scenarios can also be compiled into [VHS](https://github.com/charmbracelet/vhs)
tapes for visual screenshot capture.
## Quick start
Add `testty` as a dev-dependency in the crate that contains your E2E
tests:
```toml
[dev-dependencies]
testty = "0.6"
tempfile = "3"
```
Inside this workspace, keep using shared workspace dependencies instead:
```toml
# crates/my-app/Cargo.toml
[dev-dependencies]
testty = { workspace = true }
tempfile = { workspace = true }
```
> **Note:** `workspace = true` requires matching entries in the root
> `Cargo.toml` under `[workspace.dependencies]`.
Write a test that launches your binary, interacts with it, and asserts on
the terminal state:
```rust
use testty::recipe;
use testty::scenario::Scenario;
use testty::session::PtySessionBuilder;
#[test]
fn startup_shows_welcome() {
// Arrange
let temp = tempfile::TempDir::new().unwrap();
let builder = PtySessionBuilder::new("/path/to/my-binary")
.size(80, 24)
.env("MY_APP_ROOT", temp.path().to_string_lossy())
.workdir(temp.path());
let scenario = Scenario::new("startup")
.wait_for_stable_frame(500, 5000)
.capture();
// Act
let frame = scenario.run(builder).expect("scenario failed");
// Assert
recipe::expect_instruction_visible(&frame, "Welcome");
}
```
Run the test:
```sh
cargo test -p my-app --test e2e
```
## Core concepts
### Scenario
A `Scenario` is an ordered sequence of `Step` actions that describe a user
journey. Built with a fluent API, then executed in a PTY or compiled into a
VHS tape.
```rust
use std::time::Duration;
use testty::scenario::Scenario;
let scenario = Scenario::new("tab_navigation")
.wait_for_stable_frame(500, 5000) // Wait for app to render
.press_key("Tab") // Switch tab
.wait_for_stable_frame(300, 3000) // Wait for re-render
.capture(); // Snapshot the terminal
```
### Steps
Each `Step` represents a single user action or wait condition:
| `WriteText` | Type text into the terminal | `.write_text("hello world")` |
| `PressKey` | Send a named key press | `.press_key("Enter")` |
| `Sleep` | Pause for a fixed duration | `.sleep_ms(200)` |
| `WaitForText` | Poll until text appears | `.wait_for_text("Ready", 5000)` |
| `WaitForStableFrame` | Wait for rendering to stabilize | `.wait_for_stable_frame(500, 5000)` |
| `Capture` | Snapshot the current terminal state | `.capture()` |
**Supported key names:** `Enter`, `Tab`, `Escape` / `Esc`, `Backspace`,
`Up`, `Down`, `Left`, `Right`, `Home`, `End`, `Delete`, `PageUp`, `PageDown`,
`Space`, `Ctrl+<letter>` (e.g., `Ctrl+C`). Unknown keys are sent as raw bytes.
### PtySession and PtySessionBuilder
`PtySession` spawns the binary in a real PTY using `portable-pty`. Configure
it with `PtySessionBuilder`:
```rust
use testty::session::PtySessionBuilder;
let builder = PtySessionBuilder::new("/path/to/binary")
.size(120, 40) // Terminal dimensions (default: 80x24)
.env("DATABASE_URL", "sqlite::memory:") // Environment variables
.env("LOG_LEVEL", "debug")
.workdir("/tmp/test-workspace"); // Working directory
// Option 1: Use with a Scenario
let frame = scenario.run(builder).expect("failed");
// Option 2: Manual control
let mut session = builder.spawn().expect("spawn failed");
session.write_text("hello")?;
session.press_key("Enter")?;
let frame = session.wait_for_text("response", std::time::Duration::from_secs(5))?;
```
### TerminalFrame
A `TerminalFrame` is a snapshot of the terminal state parsed through `vt100`.
It provides structured access to text, colors, and styles:
```rust
use testty::frame::TerminalFrame;
// Create from raw ANSI bytes (done automatically by PtySession)
let frame = TerminalFrame::new(80, 24, b"\x1b[1mBold Title\x1b[0m\r\nBody text");
// Read text
let all_text = frame.all_text(); // All visible text
let row_text = frame.row_text(0); // Text from row 0
let region_text = frame.text_in_region(®ion); // Text in a region
// Search for text (returns Vec<MatchedSpan>)
let matches = frame.find_text("Title"); // Find everywhere
let matches = frame.find_text_in_region("Title", ®ion); // Find in region
```
### Region
A `Region` defines a rectangular area for scoped assertions:
```rust
use testty::region::Region;
// Named constructors
let header = Region::top_row(80); // First row, full width
let footer = Region::footer(80, 24); // Last row, full width
let full = Region::full(80, 24); // Entire terminal
let left = Region::left_panel(80, 24); // Left half
let right = Region::right_panel(80, 24); // Right half
let top_l = Region::top_left(80, 24); // Top-left quadrant
let top_r = Region::top_right(80, 24); // Top-right quadrant
// Percentage-based (col%, row%, width%, height%, cols, rows)
let upper = Region::percent(0, 0, 100, 60, 80, 24); // Top 60%
// Explicit coordinates
let custom = Region::new(10, 5, 30, 3); // col=10, row=5, 30x3
```
### MatchedSpan
When text is found in a frame, you get a `MatchedSpan` with position, color,
and style metadata:
```rust
let matches = frame.find_text("Projects");
let span = &matches[0];
span.text; // "Projects"
span.rect; // Region { col, row, width, height }
span.foreground; // Option<CellColor>
span.background; // Option<CellColor>
span.style; // CellStyle (bold, italic, underline, inverse)
span.is_bold(); // true if bold
span.is_highlighted(); // true if bold, inverse, or has background color
span.has_fg(&color); // true if foreground matches
span.has_bg(&color); // true if background matches
```
## Assertion API
### Low-level assertions (`assertion` module)
```rust
use testty::assertion;
use testty::frame::CellColor;
use testty::region::Region;
let region = Region::top_row(80);
// Text presence
assertion::assert_text_in_region(&frame, "Projects", ®ion);
assertion::assert_not_visible(&frame, "Error");
assertion::assert_match_count(&frame, "Tab", 2);
// Style checks
assertion::assert_span_is_highlighted(&frame, "Selected");
assertion::assert_span_is_not_highlighted(&frame, "Inactive");
// Color checks
assertion::assert_text_has_fg_color(&frame, "Error", &CellColor::new(128, 0, 0));
assertion::assert_text_has_bg_color(&frame, "Active", &CellColor::new(0, 0, 128));
```
All assertion functions panic with detailed messages on failure, including
the match position, actual colors/styles, and region contents.
### Recipe helpers (`recipe` module)
High-level, composable helpers for common TUI patterns. Prefer these over
raw assertions:
```rust
use testty::recipe;
// Tabs
recipe::expect_selected_tab(&frame, "Projects"); // In header, highlighted
recipe::expect_unselected_tab(&frame, "Sessions"); // In header, not highlighted
// Footer
recipe::expect_keybinding_hint(&frame, "Tab"); // Hint in footer row
recipe::expect_footer_action(&frame, "Quit"); // Action in footer row
// Content
recipe::expect_instruction_visible(&frame, "Press Enter to start");
recipe::expect_dialog_title(&frame, "Confirm Delete"); // Upper 60% of terminal
recipe::expect_status_message(&frame, "Saved"); // Anywhere in frame
// Absence
recipe::expect_not_visible(&frame, "Loading...");
```
## Snapshot testing
The framework supports two snapshot modes: **frame text** (semantic) and
**visual screenshot** (pixel-level via VHS).
### Frame text snapshots
Compare the terminal text content against a committed baseline:
```rust
use testty::snapshot::{self, SnapshotConfig};
let config = SnapshotConfig::new(
"tests/e2e_baselines", // Committed baseline directory
"tests/e2e_artifacts", // Failure artifact output (gitignored)
);
snapshot::assert_frame_snapshot_matches(
&config,
"startup_projects_tab", // Snapshot name
&frame.all_text(),
).expect("frame snapshot should match");
```
### Visual snapshots (VHS)
Compile a scenario into a VHS tape for pixel-level screenshot capture:
```rust
let tape = scenario.to_vhs_tape(
&binary_path,
Path::new("/tmp/screenshot.png"),
&[("MY_ENV", "value")],
);
// Write tape to file
tape.write_to(Path::new("/tmp/test.tape"))?;
// Execute the tape (requires VHS installed)
tape.execute(Path::new("/tmp/test.tape"))?;
```
### Updating baselines
Set `TUI_TEST_UPDATE=1` to overwrite baselines with the current output:
```sh
TUI_TEST_UPDATE=1 cargo test -p my-app --test e2e
```
### Snapshot config tuning
For visual snapshots, configure pixel-level comparison thresholds:
```rust
let config = SnapshotConfig::new("tests/baselines", "tests/artifacts")
.with_thresholds(
30.0, // Per-pixel color distance threshold (Euclidean RGB)
10.0, // Maximum percentage of differing pixels allowed
);
```
## Module overview
| `scenario` | Fluent builder for composing test scenarios from steps |
| `step` | Step enum: `WriteText`, `PressKey`, `Sleep`, `WaitForText`, `WaitForStableFrame`, `Capture` |
| `session` | PTY executor: `PtySession` + `PtySessionBuilder` |
| `frame` | Terminal state parser: `TerminalFrame`, `CellColor`, `CellStyle` |
| `region` | Rectangular region definitions with named anchors |
| `locator` | `MatchedSpan` with text, position, color, and style metadata |
| `assertion` | Structured assertion functions with detailed failure messages |
| `recipe` | High-level helpers for tabs, footer, dialogs, status messages |
| `snapshot` | Baseline management: frame text and visual image comparison |
| `vhs` | VHS tape compiler for visual screenshot capture |
| `calibration` | Cell-to-pixel geometry mapping for overlay rendering |
| `artifact` | Failure artifact directory and capture storage |
| `overlay` | Pixel-level drawing on screenshots for visual debugging |
## Full example
A complete E2E test exercising tab navigation:
```rust
use testty::recipe;
use testty::scenario::Scenario;
use testty::session::PtySessionBuilder;
use testty::snapshot::{self, SnapshotConfig};
#[test]
fn tab_key_switches_tabs() {
// Arrange
let temp = tempfile::TempDir::new().unwrap();
let builder = PtySessionBuilder::new(env!("CARGO_BIN_EXE_myapp"))
.size(80, 24)
.env("APP_ROOT", temp.path().to_string_lossy())
.workdir(temp.path());
let scenario = Scenario::new("tab_switch")
.wait_for_stable_frame(500, 5000)
.press_key("Tab")
.wait_for_stable_frame(300, 3000)
.capture();
// Act
let frame = scenario.run(builder).expect("scenario failed");
// Assert
recipe::expect_selected_tab(&frame, "Sessions");
recipe::expect_unselected_tab(&frame, "Projects");
// Optional: frame snapshot
let config = SnapshotConfig::new("tests/e2e_baselines", "tests/e2e_artifacts");
snapshot::assert_frame_snapshot_matches(&config, "tab_switch", &frame.all_text())
.expect("frame snapshot should match");
}
```
## Tips
- **Use `wait_for_stable_frame`** instead of `sleep_ms` when waiting for
rendering. It adapts to actual render speed rather than hard-coding delays.
- **Use recipe helpers** over raw assertions. They encode common TUI layout
patterns (header tabs, footer hints) so you don't rebuild locator logic.
- **Set deterministic terminal size** (e.g., 80x24) to keep frame snapshots
stable across machines.
- **Isolate state** with `tempfile::TempDir` and environment variables so
tests don't interfere with each other or the real app data.
- **E2E tests run automatically** with `cargo test`. Cargo builds the binary
before running integration tests, so `CARGO_BIN_EXE_*` is always available.