# Testing your app

> The testing framework (TestCase), tap simulation and visual comparison via screenshot.

Source: https://crossfly.dev/docs/learn/testing-your-app — CrossFly documentation. Full docs as one file: https://crossfly.dev/llms-full.txt

# 11. Testing your app

> **What you will learn:** create a safety net with tests that run in the graphics runtime.
> **Prerequisites:** [Making it responsive](/docs/learn/making-it-responsive).

## Complete example (copy, paste and run)
Unlike the other chapters, here the self-contained example is a complete `TestCase` (not a
`MainWindow`): it opens the screen in `load()`, simulates taps in `runTests()` and compares the screenshot with the
golden. `DeviceConfig.isTesting = true` makes rendering deterministic. Compiles as is.
```java
package com.exemplo;

import dev.crossfly.test.*;
import dev.crossfly.ui.*;
import dev.crossfly.ui.layout.*;

public class AdicionarTarefaTest extends TestCase
{
   @Override
   protected void load() throws Exception
   {
      DeviceConfig.isTesting = true;                 // golden prerequisite (determinism)
      new TarefasScreen().show();
   }

   @Override
   public void runTests() throws Exception
   {
      waitWindow(TarefasScreen.class);               // waits for a stable frame
      type(0, TextField.class, "Comprar pão");       // types into the 1st TextField
      click("Adicionar");                            // clicks the button by its text
      shot();                                        // captures and compares against the golden
   }

   @Override
   protected void unload() { }
}

class TarefasScreen extends Window                   // the screen under test
{
   private final TextField campo = new TextField().caption("Nova tarefa");
   private final Component listaBox = new Component();

   @Override
   public void onShow() throws Exception
   {
      super.onShow();
      setLayout(new VerticalLayout());
      add(LAY_AUTO, campo);

      Button add = new Button("Adicionar");
      add.onAction(c -> {
         String t = campo.getText().trim();
         if (!t.isEmpty()) { listaBox.add(LAY_AUTO, new Label(t)); campo.clearText(); listaBox.setValidLayout(false); repaint(); }
      });
      add(LAY_AUTO, add);

      listaBox.setLayout(new VerticalLayout());
      add(LAY_FILL, listaBox);
   }
}
```
To run the suite:
```java
new TestSuite().startTests(new TestCase[]{ new AdicionarTarefaTest() });
```
> The snippets below show **only the core** (what goes inside `onShow()`). To run them, place them in the `MainWindow` skeleton above.

## Tests run in the graphics runtime (it's not JUnit)
Each `TestCase` runs inside the paint thread/GL pipeline; the main assertion is the **visual
comparison of screenshots** (*golden images*).
```java
public class AdicionarTarefaTest extends TestCase {
   @Override protected void load() throws Exception { new TarefasScreen().show(); }
   @Override public void runTests() throws Exception {
      waitWindow(TarefasScreen.class);
      type(0, TextField.class, "Comprar pão");   // types in the field
      click("Adicionar");                         // clicks the button
      shot();                                     // captures and compares against the golden
   }
   @Override protected void unload() { }
}
```
Run with a `TestSuite`:
```java
new TestSuite().startTests(new TestCase[]{ new AdicionarTarefaTest() });
```

## ⚠️ Determinism: `DeviceConfig.isTesting`
The pixel-by-pixel comparison only matches if rendering is deterministic. Turn on
`DeviceConfig.isTesting = true` (fixes the cursor, removes timestamps) — **without it, the golden never matches**.
Use `waitWindow(...)`/`waitAnimation()` before `shot()` to capture a **stable frame**.

## Direct screenshot
```java
Image atual = Main.getScreenShot(true);   // captures the frame (opaque) to compare against the baseline
```

## What you build in this step
Tests to **add/persist** a task and a **visual test** of a screen.

## Recap
`TestCase` (`load`/`runTests`/`unload`) + `click`/`type`/`shot`; `DeviceConfig.isTesting` is
a prerequisite for the golden; capture stable frames.

## Next steps
→ [Shipping](/docs/learn/shipping)

## See also
- [Tests (best-practices)](/docs/best-practices/testes) · Canonical source: Chapter 31 — Tests