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test-vue-composable

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Guide for unit testing Vue 3 Composables using Vitest. Use this skill when writing tests for Vue logic to determine the correct testing strategy based on whether the composable is independent, relies on lifecycle hooks (onMounted), or uses dependency injection (provide/inject).

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Vue Composable Testing Guide (Vitest)

1. Determine Composable Type

Analyze the source code of the composable to determine the testing strategy:

  1. Independent: Uses only Reactivity APIs (ref, computed, watch). Does not use Lifecycle hooks or inject.
  2. Dependent (Lifecycle): Uses Lifecycle hooks (e.g., onMounted, onUnmounted).
  3. Dependent (Injection): Uses inject to retrieve dependencies.

2. Select Testing Strategy

A. Independent Composables

Test directly by invoking the function and asserting the returned state. No mocking of the Vue instance is required.

  • Pattern: Import composable -> Call it -> Assert result.value.
  • Reference: See references/examples.md (Section: Independent)

B. Dependent Composables (Lifecycle)

Requires a component context to trigger hooks like onMounted. Use the withSetup helper function.

  1. Prerequisite: Ensure test-utils.ts (or similar) exists containing the withSetup helper.
    • Action: If the helper is missing, generate it using references/helpers.md.
  2. Pattern: Import withSetup -> Call withSetup(() => useComposable()) -> Destructure result -> Assert.
  3. Reference: See references/examples.md (Section: Lifecycle Dependent)

C. Dependent Composables (Injection)

Requires a provider context. Use the useInjectedSetup helper function.

  1. Prerequisite: Ensure test-utils.ts contains the useInjectedSetup helper.
    • Action: If the helper is missing, generate it using references/helpers.md.
  2. Pattern: Define injection config array -> Call useInjectedSetup -> Assert -> Call unmount().
  3. Reference: See references/examples.md (Section: Injection Dependent)