pattern-test

Before writing tests, verify the pattern has:

• pattern() (not single-type pattern())
• Actions typed as Stream in Output interface
• Bound handlers returned from the pattern

If missing, fix the pattern first - tests can't call .send() without proper Output types.

• docs/common/workflows/pattern-testing.md - Full test file format and prerequisites

```bash

deno task ct test packages/patterns/[name]/[file].test.tsx

```

```tsx

import { action, computed, pattern } from "commontools";

import Pattern from "./pattern.tsx";

export default pattern(() => {

// 1. Instantiate pattern under test

const instance = Pattern({ / input / });

// 2. Define actions (trigger events)

const action_do_something = action(() => {

instance.someAction.send();

});

// 3. Define assertions (computed booleans)

const assert_initial_state = computed(() => instance.someField === expectedValue);

const assert_after_action = computed(() => instance.someField === newValue);

// 4. Return tests array

return {

tests: [

{ assertion: assert_initial_state },

{ action: action_do_something },

{ assertion: assert_after_action },

],

};

});

```

• Test each sub-pattern BEFORE writing the next one
• Use .send() to trigger actions (requires Stream in Output type)
• Use direct property access to read values (not .get())
• Use computed(() => boolean) for assertions

• Test file exists alongside pattern
• Tests pass
• Ready for next sub-pattern