Use Skill("ct") for ct CLI documentation when running commands.

Test Sub-Pattern

Prerequisite Check

Before writing tests, verify the pattern has:

• pattern<Input, Output>() (not single-type pattern<State>() )

• Actions typed as Stream<T> in Output interface

• Bound handlers returned from the pattern

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

Read First

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

Test Command

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

Test File Template

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 }, ], }; });

Key Points

• 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

Done When

• Test file exists alongside pattern

• Tests pass

• Ready for next sub-pattern