chore: import upstream snapshot with attribution

skills/tinystruct-patterns/references/testing.md

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+# tinystruct Testing Patterns
+
+## When to Use
+
+Use these patterns when writing unit tests for your applications with **JUnit 5**. Essential for verifying action logic, routing registration, and HTTP mode behavior.
+
+## How It Works
+
+### Unit Testing Applications
+ActionRegistry is a singleton. To test an application:
+1. Instantiate the application.
+2. Provide a `Settings` object (triggers `init()` and annotation processing).
+3. Use `app.invoke(path, args)` to test logic directly.
+
+### HTTP Integration Testing
+For tests involving the built-in HTTP server:
+1. Start `HttpServer` in a background thread.
+2. Use `ApplicationManager.call("start", context, Action.Mode.CLI)` to boot.
+3. Wait for the port to be open using a `Socket`.
+4. Use `URLRequest` and `HTTPHandler` to perform actual requests.
+
+## Examples
+
+### Unit Test
+```java
+import org.junit.jupiter.api.*;
+import org.tinystruct.system.Settings;
+
+class MyAppTest {
+    private MyApp app;
+
+    @BeforeEach
+    void setUp() {
+        app = new MyApp();
+        app.setConfiguration(new Settings());
+        app.init(); // triggers @Action annotation processing and registers all actions
+    }
+
+    @Test
+    void testHello() throws Exception {
+        Object result = app.invoke("hello");
+        Assertions.assertEquals("Hello!", result);
+    }
+
+    @Test
+    void testGreet() throws Exception {
+        Object result = app.invoke("greet", new Object[]{"James"});
+        Assertions.assertEquals("Hello, James!", result);
+    }
+}
+```
+
+### ActionRegistry Match Testing
+```java
+@Test
+void testRouting() {
+    ActionRegistry registry = ActionRegistry.getInstance();
+    Action action = registry.getAction("greet/James");
+    Assertions.assertNotNull(action);
+}
+```
+
+### HTTP Integration Pattern
+Reference: `src/test/java/org/tinystruct/system/HttpServerHttpModeTest.java`
+
+```java
+// Pattern:
+// 1. Start server in thread
+// 2. Poll for port availability
+// 3. Send HTTP request via HTTPHandler
+// 4. Assert response body/status
+```