20 Essential Postman Interview Questions and Answers for QA Testers

Postman has become an indispensable tool for API testing and development workflows. With its intuitive GUI and powerful feature set it’s no wonder that knowledge of Postman is becoming a highly sought-after skill for QA engineers and test automation roles.

If you have an upcoming job interview that involves Postman, you’ll want to make sure you’re prepared to address the key questions interviewers are likely to ask. This article will provide you with a cheat sheet of 20 common Postman interview questions along with sample answers to help you impress your future employer!

1. What is Postman and how is it useful for testing APIs?

Postman is a popular API testing tool that allows you to build, test and modify APIs through an intuitive graphical user interface. It can be used to construct API requests quickly, save them in collections to re-use later, add tests to validate responses, mock servers and much more.

For QA testers, Postman is invaluable in automating API tests without needing to write code You can easily group related requests into monitorable collections, add dynamic variables and run tests with various data inputs This level of flexibility makes Postman a go-to tool for comprehensive API testing workflows.

2. What are the key components of an HTTP request in Postman?

The key components of an HTTP request in Postman are

• HTTP method – GET, POST, PUT, DELETE etc.
• Endpoint URL
• Headers – Information like content type, accept type etc.
• Body – JSON or XML payload data
• Parameters – Query parameters for GET requests, form data for POST requests

Being able to construct requests with these elements is crucial for API testing with Postman.

3. What are some key features of Postman that you find most useful in your testing workflow?

Some key features of Postman that are often found useful in testing workflows include:

• Collections: It allows you to organize and group related requests, making managing and executing test suites easier.
• Environments: You can create multiple environments to easily switch between different configurations like test, staging, production etc.
• Global variables: Useful for dynamic data and avoiding hard-coding values.
• Pre-request scripts: Ability to execute JavaScript before a request is sent, great for setting up data.
• Tests: Writing scripts to validate API responses, crucial for API testing.
• Documentation: Auto-generated documentation from collections makes maintaining APIs easier.

4. How can you pass data between requests in Postman?

Some ways to pass data between requests in Postman are:

• Using global or environment variables to store values from one response to use in subsequent requests
• Chaining requests in a collection and accessing previous responses
• Using Pre-request scripts to prepare data
• Storing values from responses in the Postman globals
• Using Interceptors to modify in-flight requests and responses

5. How do you parameterize requests in Postman to run them with different values?

To parameterize requests in Postman, you can use:

• Collection Runner – Execute a collection multiple times with different CSV data files
• Environment variables – Define variables globally or per environment to substitute into requests
• Data variables – Create JavaScript variables dynamically initialized before each iteration
• Pre-request scripts – Generate data before each request using JavaScript

This allows you to easily iterate requests with multiple data inputs without manual intervention.

6. What types of tests can you write in Postman?

Some types of tests you can write in Postman include:

• Status code tests – To validate expected response codes
• Header tests – To check values of headers in responses
• Body tests – To validate response body contents using assertions
• Schema validation – Validate responses against a JSON schema
• Performance tests – To check response times meet thresholds
• Conditional tests – Execute subsequent tests only if a condition is met

Writing comprehensive tests is key to ensure APIs are functioning as expected.

7. How does Postman monitor collections? What are some benefits?

Postman monitors allow you to schedule collection runs at pre-defined intervals. Some benefits include:

• Automatic execution of API test suites without manual intervention
• Checking for regressions in APIs with repeated runs
• Ability to configure monitors based on schedules, iterations, delays
• Visual tracking of passing and failing tests over time
• Reporting via email or third party integrations like Slack

Monitoring is useful for continuously validating APIs and catching regressions.

8. Explain how you can mock an API server or endpoints in Postman.

There are two ways to mock servers and endpoints in Postman:

Mock Server

• Create a Postman API by defining endpoints and expected request/response structure
• Generate a mock server from the API which can receive requests
• Use the mock server URL to point API calls during testing

Mock Responses

• Add examples for each endpoint in an existing collection
• Right click on an endpoint and select “Mock Response”
• Postman will return the mocked response when that endpoint is hit

Mocking is helpful when the actual API is unavailable or incomplete during development.

9. How can you document an API in Postman?

Postman has built-in tools to help document APIs:

• Create a collection with all the endpoints needed
• Add descriptions for the overall collection as well as individual endpoints
• Include request/response details like headers, body, tests etc.
• Generate documentation – Various templates like API Blueprint are available
• Customize documentation styles as needed
• Download generated documentation or publish to Postman API documentation hosting

This enables collaborative development and maintenance of API documentation.

10. How does inheritance work in Postman collections?

Postman collections support inheritance which allows child collections to inherit entities from parent collections. For example:

• Environment and global variables
• Authentication helpers
• Pre-request scripts
• Custom code snippets
• Collection and folder-level tests

This leads to better re-use and prevents duplication across collections. Inheritance can be utilized via the “Edit Collection” options.

11. How can you run Newman and Postman collections from the command line?

Postman’s Newman CLI tool allows you to run collections directly from the command line:

• Install Newman globally via NPM
• Export the collection and environment files from Postman
• Run Newman commands like:

newman run MyCollection.json -e MyEnvironment.json

• Optional parameters like iteration data, reports etc. can also be added
• Integration into CICD pipelines is also possible by calling Newman from pipelines

12. How do you import and export Postman collections?

There are a few options to import and export collections:

Export

• From within Postman app, use “Export” button for a collection
• Choose format – Postman Collection (JSON) or Collection v2
• Collection JSON will download to your machine

Import

• “Import” button in Postman
• Select type as “Postman Collection”
• Upload JSON file to import

Other Options

• Import/export from Postman API
• Utilize collection links to share easily

13. Explain how you can use collection and environment variables in Postman.

There are two types of variables in Postman:

Collection variables

• Declared at collection level
• Available across entire collection by default
• Helpful for data like base URLs, common headers etc

Environment variables

• Declared at environment level
• Scoped to a particular environment
• Used for environment-specific data like host addresses, credentials
• Useful for multi-environment testing

Using variables avoids hard coding values and makes collections more dynamic. The appropriate scope should be chosen based on reusability needs.

14. How can you debug failed requests and tests in Postman?

Some ways to debug failed requests and tests:

• Inspect request headers, body, URL closely to check for errors
• Use the Postman console to log useful debug statements using console.log
• Leverage breakpoints in tests to pause execution and inspect data
• Use the browser debugger built into Postman’s desktop apps
• Take advantage of reactive tracing for network-level debugging
• View environment, global and local variable current values
• Check assertions for expected vs actual results

Thorough debugging helps identify root causes for failed requests and tests.

15. What are some best practices you follow for API test automation with Postman?

Some API testing best practices with Postman:

• Maintain well-organized collections with descriptive names
• Modularize requests into smaller collections where possible
• Parameterize collection so data can be supplied externally
• Make use of collection-level tests for common validations
• Use variables over hard-coded values within requests
• Create dedicated test suites to validate related flows
• Implement robust error handling in test scripts
• Monitor collections on a frequent basis to catch regressions
• Generate comprehensive documentation for reference

These practices help build more maintainable, reusable test suites.

16. How can you integrate Postman with Continuous Integration tools like Jenkins?

Postman provides a Newman command-line collection runner that enables