Bank Account Simulation Class With Self-Written Tests at 90% Coverage

Bank Account Simulation Class With Self-Written Tests at 90% Coverage

Company: Shopify

Role: Software Engineer

Category: Software Engineering Fundamentals

Difficulty: medium

Interview Round: Technical Screen

Overview: A pair-programming exercise: implement a class that simulates bank account operations, write your own tests reaching at least 90% coverage, and then extend the working code with a new requirement. It tests invariant-driven validation, all-or-nothing transfers, meaningful test design, and clean incremental changes.