Swagger Interview Questions

This Swagger Interview Questions article covers all key concepts like Why, how, Document APIs, Data formats, security and many more to help you ace the Swagger job interviews. Let us go through the blog.

 

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Swagger is the mainstream technology for documenting APIs. When installing APIs in Azure, Swagger comes in handy. Swagger is largely used to document APIs; however, why should APIs be documented? The concept is the same for designing APIs that are internal in the organization or for public consumption, as it is for the apps that developers are creating.

 In this blog, you will find Types of Swagger Interview Questions

Top Swagger Interview Questions and Answers

Our expertise covered basic to advanced concepts and curated Swagger Interview Questions and Answers, let's have a look into them.

1. Why use OpenAPI?

2. How does the Web API work?

3. What happens when I publish the API in SwaggerHub?

4. Explain Documentation in Swagger?

5. Explain the term Operations?

Swagger Interview Questions and Answers for Freshers

Q1). What is Swagger?

Ans: Swagger is being used to share documents among developers, testers, and product managers, as well as to automate API-related tasks through various technologies. OpenAPI Specification (OAS), which includes both open source and professional tools, is also utilized in the development of APIs.
Swagger also assists in defining the structure of our APIs so that machines may read them. It accomplishes this by requesting that our API return JSON or YAML including a full description of our API. The major Swagger tools include:

  • Swagger Editor—- It is a browser-based editor for writing OpenAPI specifications.
  • Swagger UI—- Creates dynamic API documentation from OpenAPI specifications.
  • Swagger Codegen—- from an OpenAPI specification, it creates server stubs and user libraries.

Q2). Why use OpenAPI?

Ans: All of OpenAPI's brilliance stems from APIs' ability to explain their structure. An OpenAPI definition and Swagger tools, once written, can help you advance your API development in a variety of ways: 

  • Users who prioritize design: To create a server stub for your API, utilize Swagger Codegen. Only the server logic needs to be implemented, and your API is ready to go live!
  • Swagger Codegen can produce packages in over 40 languages for your API.
  • Swagger UI allows you to create immersive API documentation that allows your users to try out API requests in the browser.
  • Integrate API-related tools to your API using the spec. Import the standard into SoapUI, for example, to perform automated API tests.

Q3). What is API?

Ans: API is the abbreviation for Application Programming Interface. It specifies how two modules of software communicate with one another. There are various types of APIs, but the swagger is focused on the Web API.

If you want to enrich your career and become a professional in OpenAPI, then enroll in "OpenAPI Online Training" - This course will help you to achieve excellence in this domain.

Q4). How does the Web API work?

Ans: Let's take a look at how the Web API works using an example. Assume we are using Facebook on our phone and send a connection request to the Facebook server. An API request is a request that is sent to the Facebook server, and the Facebook server responds with an API response. The data will be sent by the server, not the entire web page. It is the app's job to show the web page.

The following is how API definition works in this case:

  • What kind of requests are there?
  • What does each request's response looks like.

The Open API and Swagger specifications are primarily developed for the Rest API, where Rest is a type of web API. The term R stands for Representational, S for State, and T for Transfer in the phrase Rest.

Q5). What is API Definition and why to create it?

Ans: The API Definition is a document that lists all of the activities we can accomplish using an API. It encapsulates all of the API calls that we can make. It also explains how to make a request and what the result will be for each request.

Q6). What is the purpose of an API definition?

Ans: There are numerous benefits of writing an API definition:

  • It enables you to design the API before placing it into action. Before writing a program for the API, the programmers can review it.
  • It's also beneficial for automated testing.
  • It can generate code in a number of languages dynamically.
  • It can also be used to automatically generate documentation.

Q7). What happens when I publish the API in SwaggerHub?

Ans: Publishing an API indicates that it is in a stable state, that it will function as intended, and that it is suitable for consumption by applications. When you expose an API on SwaggerHub, it becomes read-only, and you can only update it if you unpublish it. If you need to edit the description content or address mistakes, it's fine to temporarily unpublish an API. However, for major modifications, such as additional operations or arguments, you should create a new version using the SwaggerHub editor's Add Version function. SwaggerHub allows you to keep track of various versions of an API definition, allowing you to work on the next edition while maintaining the current version (the "production" version).

Q8). What are the integrations that are available in SwaggerHub?

Ans: SwaggerHub is designed to let organizations interact throughout the API lifecycle. As a result, SwaggerHub integrates the API development tools that organizations rely on. These are some of the integrations:

  • SCMs: Integrate your API with BitBucket and GitHub
  • API Management: Integrate your API to Microsoft Azure, Lambda, and Amazon API Gateway.
  • Mocking: VirtServer allows you to virtualize API activities.
  • Webhooks: Webhooks can be used to trigger bespoke activities.
  • Testing: APIs can be imported into Ready! API for continuous testing

Q9). Explain Documentation in Swagger.

Ans: The API file or OAS contains an understandable description of the components that are used to automatically produce documentation. To put it another way, an explanation component has been added to the API, as well as to each operation (which is a combination of method and path ), each argument, and each component response.

Q10). Explain Structured Data Formats.

Ans: The structured data format is used by the Open API Specification for its API configuration files. One of the two structured forms, YAML or JSON, can be used.

YAML: The abbreviation YAML stands for "Ain't Markup Language." It is not a scripting language in the same way that HTML is. It's only used for data, not for content. In comparison to JSON and XML, YAML employs the fewest characters possible. It's more commonly used for configuration files than for files that are sent over the web, such as JSON.
keys and value pairs
The information in YAML is represented using key/value pairs. A colon accompanied by a space denotes key/value pairs.

For Instance: 

Date: 2022-02-14  
Name: Mindmajix  

In the above example, Name and Date are the keys, and Mindmajix, 2022-02-14 are the values.

Levels: White space indenting is used to show levels, however, we can't use tab indent. This is the most significant distinction between YAML and other structured forms. XML uses tags to add one level, and then add tags inside the tag to add another, increasing the number of characters. Opening and closing braces in JSON denote a single level that spans many characters. Only indentation is utilized in YAML, which takes up fewer characters. 

XML:

 1. <Name>  
 2. <last name> Magics</last name>  
 3. <first name> Mind </first name>  
 4. </Name>

JSON:

 1. name: {  
 2. "lastname": "magics"  
 3. "firstname": "mind"  
4.  }

YAML:

1. name:  
2.  lastname: magics  
3.  firstname: mind  
4.

Types:  The types in YAML are specified from the context.

For example:

  • part_numb: 1234
  • description: Online
  • price: 3.3
  • quantity: 6

In the above scenario, the quantity is considered as an integer, price is considered as a float value, part_numb and description will be considered as a string.

List: The YAML list is similar to the JSON list. To denote a list item, we must use a dash. The list does not need to be declared.

cart:  
  -part_numb: 1234
description: Maggie
price: 3.3
quantity: 6

-part_no: 2356
   Description: Lemon
   color: green 
   price: 1.3
   quantity: 24

The cart is the title of the list, and there are two list items in the cart, as we can see in the sample above. The dash is used to denote both list items. The first list item has four key-value pairs, while the second list item has five key-value pairs.

Multi-line Strings: 
 
Because strings do not include quotation marks, identifiers are required for multiline strings. For multi-line strings, the following characters are used:
|: It keeps the spaces and lines  
>: Fold lines 

1. S: |  
2. YAML  
3.     and JSON. 
4. 

In the above instance, we have utilised the '|' character so its output would be the same as it is written above.

Output: 
 YAML
   And JSON

If we use '>' character the output would be as follows.

Input code:  
S:>
YAML
   And JSON

Output: 

YAML and JSON

Swagger Interview Questions and Answers for Intermediate Candidates

Q11). How does SwaggerHub help with documenting my API?

Ans: The following documentation is available via SwaggerHub. Within the Interactive Docs page, users may define and describe every component of the API right on the Swagger Editor, and have them presented visually for end consumers to work with, understand, and connect.

With our in-built HTML download of the API, users can create a rudimentary dev portal-like experience. You can obtain a bootstrap sample version of your API documentation that illustrates your endpoints with six distinct client SDKs, with the option to add more.

Q12). Does SwaggerHub support JSON or YAML?

Ans: The Swagger (Open API) 2.0 syntax is supported by SwaggerHub for defining APIs. YAML is the standard format for API declarations. You can also paste JSON content; however, when you save your API definition, it will be transformed to the YAML format.

Related Article: Apigee vs Swagger

Q13). How do I mock an API backend Server?

Ans: SwaggerHub interfaces with VirtServer, a component of developing alternative API virtualization. The VirtServer Integrate produces and maintains a semi-static fake of an API specified in SwaggerHub when it is configured. You no longer need to discover and utilize additional tools to construct mock services because this mock is maintained every time you save the API. With only a few clicks, you may iterate on the layout with your team using the preview created by the VirtServer. When it comes to debating API design, the mock server can be a useful tool. You can allow API clients to construct clients against the VirtServer without writing a single line of code, and the VirtServer is assured to react with realistic payloads, compatible.

Q14). Explain the term Path?

Ans: Pathways are terminals (resources) that your API provides, such as summary/users or /reports, and actions are the HTTP procedures used to alter these paths, such as DELETE, POST, GET in OpenAPI terms.

Paths
The global pathways portion of the API standard defines API operations and paths.

paths:
 /message
   ...
 /users:
   ...
 /users/{id}:
   ...

The API server URL is used as the starting point for all pathways. server-url>/path is the full URL for the request. On the path or operation level, global servers can likewise be overridden (more on that below). For documentation purposes, paths may contain a short summary and a lengthy description. This data is expected to apply to all operations along this path. description supports Markdown (CommonMark) for rich language modelling and can be multi-lined.

paths:
 /users/{id}:
   summary: User
   description: >
     This resource depicts an individual user in the system.
     Every user is identified by a numeric `id`.

   get:
     ...
   patch:
     ...
   delete:
     ...

Path Templating: 
You can utilize curly braces {} to indicate parts of an URL as path parameters:
/users/{id}
/organizations/{orgId}/members/{memberId}
/report.{format}

When performing an API call, the API client must supply proper parameter values, such as /users/12 or /users/5.

Q15). Explain the term Operations?

Ans: Define operations (HTTP methods) for each path that can be used to access it. Get, put, delete, head, post, trace are all supported in OpenAPI 3.0. A single path can be used for several activities, such as GET /users to retrieve a list of users and POST /users to create a new user. A unique operation is defined by OpenAPI as a combination of a path and an HTTP method. This means that you can't use two GET or two POST procedures for the same path, even if the arguments are different (attributes have no effect on uniqueness). Here's a simple example of a procedure:

paths:
 /message:
   get:
     responses:
       '100':
         description: ok

For documentation purposes, operations additionally support the following optional elements: 

  • A summary of what a procedure performs, as well as a more detailed description. characterization implements Markdown (CommonMark) for rich text representation and can be multi-lined.
  • Tags are used to logically classify activities based on resources or other qualifiers. See Using Tags to Group Operations.
  • externalDocs - a reference to an external site that includes more information.

Q16). Explain about parameters and types of parameters.

Ans: Parameters are determined in the attributes component of the operation or the path in OpenAPI 3.0. A parameter's name, placement (in), the data type (specified by either content or schema), and other qualities, like description or necessity, are all used to characterize it. Here's an illustration: 

paths:
  /users/{userId-numb}:
    get:
      summary: userid-number
      parameters:
        - in path
          name: userId_name
          schema:
            type: int
          required: true
          description: User number_Id
Because parameters is the array, every parameter definition in YAML must have a dash (-) ahead of it.

Parameter Type:

Based on the parameter location, OpenAPI 3.0 differentiates the below parameter types as per parameter location. The parameter's in the key, for instance, in a query or a path, depends on the position.

  • Path parameters, like /users/id
  • query parameters, like /users?role=admin
  • header parameters, like X-MyHeader: Value
  • cookie variables, which are managed to pass in the Cookie header, like Cookie: debug=0; csrftoken=BUSe35dohU3O1MZvDCU

Path Parameter: 

The different elements of the URL path are referred to as path parameters. They're usually used to connect to a particular resource in a database, like a user with a unique ID. A URL may have many path parameters, each of which is indicated by {} curly brackets.

GET /user/{id}
GET /bike/{bikeId}/drivers/{driverId}
GET /report.{format}

When a client performs an API request, each path argument must be replaced with a valid value. The in path parameter in OpenAPI is used to establish the path parameter. The name of the parameter must match that of the path. Remember to include the needed: true attribute, as path parameters are permanently necessary. The /users/id endpoint, for example, would be represented as:

paths:
  /user/{id}:
    get:
      parameters:
        - in path
          name: id # Note the name is the same as in the path
          required: true
          schema:
            type: int
            minimum: 2
          description: The user ID

In Path Parameters, we can serialize the objects and array in various ways:

  • /color, for example, is a dot-prefixed label expansion.
    R=100.
    G=200.B=150
  • path-style expansion(matrix)-semicolon-prefixed
  • /users/12,34,56 is an example of a simple-style comma-delimited list.

Style and Explode keywords define the serialization mechanism.

Query Parameter:

The most popular type of parameter is a query parameter. They occur after a quotation mark (?) at end of request URL, with diverse name=value pairs isolated by ampersands (&). Optional and required query parameters are also possible.

GET /pets/findByStatus?status=available 
GET /notes?limit=50&offset=100

Use in: query for donating query parameters:
     parameters:
        - in query
          name: offset
          schema:
            type: integer
          description: The number of items to skip before starting to collect the result set
        - in query
          name: limit
          schema:
            type: integer
          description: The number of items to return

Header Parameter:

Custom headers may be required by the API call while sending the HTTP request. The Custom request headers can be defined as header parameters in OpenAPI. Assume that a GET /ping request needs an X-Request-ID header:

  • Host: example.com
  • GET /ping HTTP/1.1
  • X-Request-ID: 77e1c83b-7bb0-437b-bc50-a7a58e5660ac

Cookie Parameter:

Cookie: name=value is a way for operations to pass arguments in Cookie header. A semicolon and a space are used to separate several cookie parameters in same header.

  • GET /api/users
  • Host: example.com
  • Cookie: debug=0; csrftoken=BUSe35dohU3O1MZvDCUOJ

Q17). What is meant by API Testing?

Ans: API Testing aids in the evaluation of an application program interface's performance, security, dependability, and functionality. It is accomplished by sending a request to one or more API Gateways and correlating the response to the outcomes. API testing has been carried out on essential layers such as Business transactions and Business Logic Processing via the Database layers and User Interface.

Q18). Explain Parameter Serialization.

Ans: Serialization is the process of converting data structures or item states into a format that can be communicated and afterwards reconstructed. OpenAPI 3.0 allows you to specify how these parameters should be serialized and supports objects and arrays in process parameters (header, query, cookie, and path). The style and explode keywords specify the serialization method: style determines how many values are delimited.

  • The types of styles available are determined on the parameter's placement – path, query, header, or cookie.
  • explosion (true/false) controls whether arrays and objects create individual parameters for each array item or object property.

The OpenAPI encoding rules are based on a component of RFC 6570's URI template patterns. To handle serialization, tool integrators can use current URI template libraries.

Swagger Interview Questions and Answers for Experienced Candidates

Q19). Explain the term Schema.

Ans: PUT and POST methods, for example, require additional data, and these techniques are referred to as HTTP methods. The request body is the object that contains these methods. The data in the content of a request can be formatted in either JSON or XML.
A JSON format can be used to represent all of the responses in a response body. Schema primarily determines the data's structure. The JSON Schema Specification provides the foundation for the OAS schema object. The data schema helps determine what the keys in key/value pairs are and what type of data the values are. A schema can have multiple levels.

$ref

The $ref is a unique OAS key that denotes that the object is a reference to another structure in the YAML file. It's useful because it reduces the number of indentation levels in the YAML file.

Q20). What is meant by Request Body?

Ans: Typically, request bodies are used with "create" and "update" operations (PUT, PATCH, POST). When using POST or PUT to generate a resource, for example, the request body normally provides a description of the resource to be produced. The request body keyword in OpenAPI 3.0 is used to specify request bodies.

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Differences From OpenAPI 2.0

If you've used OpenAPI 2.0 before, here's a quick rundown of what's new in OpenAPI 3.0:

  • The request body takes the place of the body and forms parameters.
  • Form data as well as other media types such as JSON can now be consumed by operations.
  • The request body. content map replaces the consumes array, mapping media types to their schemas.
  • Schemas differ depending on the type of medium.
  • Alternate schemas can be specified using anyOf and oneOf.
  • Objects can now be included in form data, and the serialization mechanism for objects and arrays can now be specified.
  • Request bodies are no longer allowed in GET, DELETE, and HEAD because they lack clear semantics as defined by RFC 7231.

Q21). What is meant by Response?

Ans: All API actions must have replies specified in an API standard. At least one answer, usually a successful response, must be defined for each operation. The data retrieved in response body and/or headers, as well as the HTTP status code, characterize a response. Here's a basic example: 
paths:

/msg:
 get:
 responses:
 '100':
 description: okay
 content:
 text/plain:
 schema:
 type: string

Q22). Explain Data Models.

Ans: The data types in OpenAPI 3.0 are based on a version of JSON Structure Configuration Wright Preview 00. (aka Draft 5). A Schema object is used to represent data types. See the following topics to understand how to analyze various data types:

  • Data Types
  • oneOf, anyOf, all, not
  • Representing XML
  • Dictionaries, Hashmaps, Associative Arrays
  • Enums
  • Inheritance and Polymorphism
  • Supported JSON Schema Keywords

Q23). Explain the Swagger data types.

Ans: The type keyword, for instance, type: string, define the data type of a model. The following fundamental types are defined by OpenAPI:
a line ( dates and files)
boolean
number
array
integer
object
Many programming languages have these kinds, although they could go by various names. You can represent any data structure with these types.
That there's no null type; rather, the nullable attribute is applied to the underlying type as a modifier.

To refine the data type, various kinds of keywords can be added, such as limiting the string length or specifying an enum of potential values.

Q24). Explain about Enums.

Ans: To define possible values for a request parameter or a model parameter, use the enum keyword. For instance, the sort parameter in GET /items?sort=[asc|desc] can be defined as following:
paths:
  /product_items:
    get:
      values:
        - in: query
          porduct_name: sort
          product_description: Sort order
          schema:
            product_type: string
            enum: [asc, desc]

Q25). What about Dictionaries, Hashmaps, and Associative arrays?

Ans: A dictionary is a collection of value/key pairs (also termed as an associative array, hashmap, map). OpenAPI allows you to create dictionaries using strings as keys. Use the type: object keyword to construct a dictionary, and the additional properties keyword to indicate the type of entries in value/key pairs. For instance, consider the following string-to-string dictionary:
{
  "sp": "Spanish",
  "en": "English"
}
is described using the following schema:
type: item
additionalProperties:
  type: string

Value Type:

Additional characteristics A certain kind of value in the dictionary is specified by the keyword. Primitive values (boolean, strings, and numbers), arrays, and objects can all be used as values. A string-to-object dictionary, for instance, can be specifically defined:
type: item
additionalProperties:
  type: item
  properties:
    code:
      type: integer
    text:
      type: string

Q26). Explain Authentication and Authorization.

Ans: Authentication and authorization systems are referred to as security schemes in OpenAPI. APIs secured by the accompanying security techniques can be described using OpenAPI 3.0:
The following HTTP authentication mechanisms (which use the Authorization header) are used:

  • Basic
  • Bearer
  • RFC 7235 and the HTTP Authentication Scheme Registry define various HTTP schemes.
  • API keys can be found in headers, query strings, and cookies.
  • Authentication through cookies
  • OpenID Connect Discovery with OAuth 2

Changes from OpenAPI 2.0

If you're using OpenAPI 2.0 before, here's a quick rundown of what's new in OpenAPI 3.0:

  • Security specifications have been renamed as security features and have been integrated within components.
  • type: http and scheme: basic were substituted for type: basic and scheme: basic, respectively.
  • The scheme keyword identifies the scheme type, and the new type: HTTP is an encompassing type for all HTTP security features, including Bearer, Basic, and others.
  • A cookie can now be used to send API keys.
  • Compatibility for OpenID Connect Discovery has been added (type: openIdConnect).
  • Multiple flows can now be defined in OAuth 2 security schemes.
  • access code has been renamed authorization code, and the application has been renamed client credentials to follow the OAuth 2 Specification.

Conclusion:

Our blog ends here. We hope our Best Swagger Interview Questions will help to clear your interview. Any Questions/suggestions please mention them in the comment section. 

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About Author
Madhuri Yerukala

Madhuri is a Senior Content Creator at MindMajix. She has written about a range of different topics on various technologies, which include, Splunk, Tensorflow, Selenium, and CEH. She spends most of her time researching on technology, and startups. Connect with her via LinkedIn and Twitter .

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