SDET interview questions

Purpose

The purpose of the interview is to determine level of hard and soft skills and to check that person fits team mentally.

Approach

• prefer open questions: ie. questions without one correct answer.
• when asking binary questions, mix yes and no questions. Don't coerce everything into yes or no.
• ask not only about what, but also about when and why explanations.

Structure

• greeting and small-talk
• project introduction
• soft skills (past experience, English level, etc.)
• hard skills
• Q&A

Soft skills

• Role on previous project (what was doing, team size, what learned, etc)
• How frequently was your product released? Your involvement in the releases?
• Development methodology (Scrum, Kanban, Warefrall). When to use what?
• QA process (code review, code intelligence, CI/CD)
• Good/bad practices
• Ideal QA/delivery process (Jira, VCS, CI/CD)
• Notable tools

Theory

General QA

• Testing pyramid
• Test documentation
• Functional vs integration vs e2e tests
• What's easier to test: monolithic application or microservices?
• Who should be responsible for quality?
• Who should test?
• When should automation start?
• Shift left/right

Test design

• Provide test cases for application with an input field that accepts 0 - 10 numbers (inclusive). Decimals are allowed and will be rounded to the whole number using mathematical rounding. Application saves Integer in the DB.

Computer science

• OOP (4 principles, basic use cases)
• Design Patterns
• Anti-patterns
• Clean code (SOLID, GRASP, DRY, YAGNI)
• Algorithms (Big O notation, basic algorithms)
• Multiple inheritance
• Composition/aggregation vs inheritance
• Method vs function

General QA automation

• Test framework design/architecture (basic approaches, organization, must-use patterns)
• Metrics: limiting test run time and resource utilization/test run optimization
• Configs
• Data preparation and cleaning
• Logs
• Reporting
• CI integration
• Tool integration

Java

• primitives/objects
• mutable/immutable
• var (if Java 11)
• interfaces vs abstract classes
• annotations
• override/overload
• collections
• list/set/map
• hash map/hash set
• stream
• lambdas
• optional
• generics
• equals and hashCode
• deep clone/shallow clone
• exceptions (checked/unchecked/errors)
• try/catch/finally
• static (method, variable)
• final (class, method, variable)
• access modifiers (default for class, interface)
• constructor/initializer
• JMM (heap/stack, garbage collectors, happens before, reordering, JIT)
• multithreading (asynchronous execution, reactor, locks, synchronization, thread pool, executor service, future)
• jUnit/TestNG/... (testability, mock vs stub vs spy, annotations, configuration, parallel run, parametrization)
• Maven/Gradle/... (role, configuration, dependencies, plugins, phases)

Python

• code style/quality (PEP8 / PEP20)
• mutable/immutable data types
• constructors (how to implement?)
• tuple vs list vs set
• list/dict comprehension
• the difference between v2 and v3
• is vs ==
• lambdas
• generators vs iterators
• dict
• decorators
• magic methods
• type hints
• arguments (*args, **kwargs)
• global/nonlocal
• is Python interpreted or compiled
• slicing (list, str)
• how to reverse iterable object
• try/catch/finally
• keyword pass
• keyword with (context manager)
• keyword yield
• copy/deepcopy
• keywords break/continue/pass
• venv/pipenv
• _var and __var (protected vs private)
• multithreading/asynchronous code
• GIL

Spring Boot

• The main idea behind Spring (IoC, Proxy)
• Differences between Spring (MVC) and Spring Boot
• Main annotations and their roles
• Bean scopes (default bean scope)
• Bean cyclic dependency

Hibernate

• JDBC/Hibernate/Spring Data
• Entity
• Entity relations
• N+1 problem

pyTest

• fixtures
• fixture scopes
• parallelism
• hooks
• parametrization
• marks

Selenium

• page object
• waits (interaction between implicit and explicit during waiting for object to disappear)
• remote driver
• selectors
• findElement/findElements return type in case of failure
• StaleElementException
• On what part of element will Selenium click?
• Element not clickable at point
• Download/upload file
• JS executor
• Actions
• basic auth (http)
• avoid login in every new test
• Parametrized locator
• DOM

XPath

• Differences / and //
• Differences . and ..
• Wildcard *
• Keyword contains
• Search by text
• Get parent element

REST

• relation to HTTP
• methods
• differences between GET and POST
• differences between PUT and POST
• PATCH, HEAD, OPTIONS
• idempotency
• query string (what is used for, limitations)
• components (verb, header, body, etc)
• supported markup languages
• status codes
• streaming (WebSockets / HTTP2)

Microservices

• SOA vs DDD
• REST
• gRPC/Protobuf
• Kubernetes
• Docker
• Service discovery
• Cloud-agnostic tools
• Graceful degradation
• Circuit breaker
• Saga

Git

• fetch vs pull
• merge vs rebase
• merge conflict
• force-push (what --force-with-lease does?)
• revert commit
• squash
• stash
• reset (—mixed, --hard, --soft)
• merge —abort
• fork

SQL

• SQL/noSQL
• noSQL DB types (key-value, document-oriented, wide-column, time series)
• basic syntax
• joins
• subqueries
• group by / having
• distinct
• union
• indexes
• transactions (isolation levels)
• normalization
• Transaction isolation level
• CAP theorem
• ACID

Docker

• container vs image
• networking (network types, ports, discovery)
• containerization vs virtualization
• Dockerfile: FROM, ADD, COPY, RUN, CMD, ENTRYPOINT
• docker pull/info/stats/images
• latest tag
• data persistency (volumes, mounts, permissions)
• compose
• swarm

Networking

• address vs netmask
• ISO/OSI
• bridging vs routing vs switching
• protocols (tcp, udp, icmp)
• routing (BGP, OSPF)
• DHCP
• ARP
• VPN and VLAN
• packet anatomy

Jenkins

• Jobs
• Pipelines
• Jenkinsfile
• Built-in environment variables
• Useful plugins

Linux

• logs
• change permissions
• open file (read/update)
• create/rename/remove/copy file
• default env variable value :-
• stop process
• find file

Cloud

• cloud native technology benefits
• lift and shift issues
• cloud issues
• IaaC (Cloud Formation, Terraform, Pulumi)
• Serverless

Leadership

• Conflicts inside the team
• Project estimation
• Team velocity and performance
• Firing people
• What to do if a team member refuses to work?
• Team stabilization/working with attrition and demotivation/burnout

Extra

• Mock vs stub vs spy
• Wiremock / MockServer and similar (mock TCP server)
• BDD (example of BDD test, when to use / not use)
• JSON / XML
• CI/CD (Jenkins/GitLab, integration, jobs, pipelines)
• GitHub actions
• Linux (command line, ssh, find/locate, pipes, editors, resource monitoring, logs, access rights)
• NoSQL (time-series DBs, keys, nesting, hot keys, deduplication, normalization)
• Message queues (RabbitMQ, Kafka, concepts, delivery guarantee)
• VCS (Git, Mercurial) (branches, pull-requests, rebase vs merge, cherry-pick, hooks, git flow)
• Code Intelligence (SonarQube, CheckStyle, FindBugs, pyLint)
• Code Coverage (JaCoCo, Cobertura)
• Cloud (cloud-native, infrastructure as a code)
• Docker & K8s (Dockerfile, docker build context, docker-compose, networks, sharing resources, k8s: pod, service, deployment)
• Performance (tools, concepts, isolation, bottlenecks, metrics, percentiles)
• Monitoring (Graphite, InfluxDB, Grafana)
• Reporting (Allure, ReportPortal)

Practical

Coding

• write recursive poller / classic poller
• write counter method for dict
• write simple decorator to track a time spent for method
• write method which check that int list contains only even values
• write method which check that string json has correct open-close brackets

Selenium

• Get text of elements (ex. table) and create a dict with it (extra: build a model for this)

<html>
  <body>
     <table>
        <tr>
           <th>First name</th>
           <th>Last name</th>
           <th>Age</th>
        </tr>
        <tr>
           <td>Jill</td>
           <td>Smith</td>
           <td>50</td>
        </tr>
        <tr>
           <td>Eve</td>
           <td>Jackson</td>
           <td>94</td>
        </tr>
     </table>
  </body>
</html>

• Fill all the inputs in the form

<html>
  <body>
     <div class="form">
        <div class="input">
           <label>Input - 1</label><br>
           <input class="form_input" name="1" type="text">
        </div>
     </div>
     <div class="input">
        <label>Input - 2</label><br>
        <input class="form_input" name="2" type="text">
     </div>
     </div>
     <div class="input">
        <label>Input - n</label><br>
        <input class="form_input" name="n" type="text">
     </div>
     </div>
     </div>
  </body>
</html>

• Click behind the loader (what will be? how to avoid?)
• Login with API (how to implement?)
• Write/describe a simple page object
• Write/describe BasePage methods

API

• Get ids of users who entered in September from the API response

[
 {
   "id": "_4FG12Y7U6",
   "company": "Avionics Inc.",
   "firstname": "John",
   "lastname": "Doe",
   "entered": "2013-06-12T10:00:00Z"
 },
 {
   "id": "_4FG12Y7TX",
   "company": "Avis World Headquarters",
   "firstname": "Steve",
   "lastname": "Herbin",
   "entered": "2013-09-10T10:00:00Z"
 },
 {
   "id": "_4FG12Y7TV",
   "company": "BGP Productions",
   "firstname": "German",
   "lastname": "Vicencio",
   "entered": "2013-09-30T12:46:40Z"
 }
]

• Write/describe BaseApi methods

SQL (dialect-dependent)

• Write UPDATE request
• Write INSERT request
• JOIN (types? differences? write request)
• Write request with COUNT
• Write request with GROUP BY
• Write request with HAVING
• Unique values (DISTINCT)
• Transactions

Study plan

• Basic programming language course (OOP + Design patterns + Data structures + Code standards/conventions)
• Test framework (TestNG/JUnit - Java Pytest - Python)
• Selenium
• Page Object
• API automation
• DB automation
• Git
• Build systems (Maven/Gradle - Java pip/pipenv - Python)
• Jenkins
• Docker
• CodeCoverage/CodeIntelligence