Give a simple example of Jest test case

Peer-reviewed by HireXTech Technical Panel • Updated for 2025/2026 hiring • Editorial standards

Interviewer Expectations for this Question

Core Competency

Assesses fundamental understanding of React conventions, runtime behavior, and memory/performance considerations.

Evaluation Criteria

Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.

Comprehensive Model Answer Verified Solution

Let's write a test for a function that adds two numbers in sum.js file:

     const sum = (a, b) => a + b;

     export default sum;

Create a file named sum.test.js which contains actual test:

     import sum from "./sum";

     test("adds 1 + 2 to equal 3", () => {
       expect(sum(1, 2)).toBe(3);
     });

And then add the following section to your package.json:

     {
       "scripts": {
         "test": "jest"
       }
     }

Finally, run yarn test or npm test and Jest will print a result:

     $ yarn test
     PASS ./sum.test.js
     ✓ adds 1 + 2 to equal 3 (2ms)

## React Redux

Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.

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