javascript / expert
Snippet
Reactive State Proxy Interception in Unit Test Harnesses
Unit testing stateful reactive structures without full component mounts requires intercepting Proxy operations. Wrapping a reactive store in a secondary handler proxy allows non-intrusive mutation telemetry recording during assertion verification.
snippet.js
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import { reactive, isReactive } from 'vue';export function createMutationTracker(targetState) {const mutations = [];if (!isReactive(targetState)) {throw new TypeError('Target state must be reactive');}const spyProxy = new Proxy(targetState, {set(target, property, value, receiver) {mutations.push({ property, oldValue: target[property], newValue: value });return Reflect.set(target, property, value, receiver);}});return { spyProxy, getMutations: () => [...mutations] };}
vue
Breakdown
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if (!isReactive(targetState)) {
Ensures state trap initialization only targets valid Vue reactive proxy objects.
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const spyProxy = new Proxy(targetState, {
Wraps the reactive state in a secondary Proxy handler to record set mutations.
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mutations.push({ property, oldValue: target[property], newValue: value });
Logs state mutation telemetry for assertions in automated component test suites.
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return Reflect.set(target, property, value, receiver);
Forwards property mutation seamlessly to underlying Vue reactive trap handlers.