Category: Postman

The provided text details a comprehensive course on automated API testing using Postman, guiding users from manual testing to full automation. It introduces Postman’s interface, including workspaces and collections, and demonstrates manual API testing by interacting with a mock coffee shop API. The course then transitions to writing tests with JavaScript, covering variables, data types, functions, and JSON parsing. Key concepts explored include handling API keys and secrets, asserting expected behaviors in responses (status codes, headers, body, and schema validation), and leveraging Postman’s assertion library (Chai JS). Finally, the text explains automating collection runs using the Postman Collection Runner, scheduled runs in the Postman Cloud, and integrating with CI/CD pipelines via Postman CLI and GitHub Actions to ensure continuous API health and testing.

Mastering API Testing with Postman

API testing is a crucial type of software testing that verifies the functionality, reliability, performance, and security of an Application Programming Interface (API). Its primary goal is to ensure that an API behaves as expected by examining it from the viewpoint of an external user or consumer, ideally finding issues and defects before it is released. APIs have become the backbone of software development, making API testing an essential skill for developers and testers.

Here’s a detailed discussion of API testing:

1. Purpose and Importance of API Testing

• API testing ensures that an API works correctly. It’s likened to quality control in a car factory, where a car undergoes various inspections before being deemed road-ready.
• It focuses on examining the API to ensure it behaves as expected, helping to find issues and defects before the API is made available to users.
• The course “Postman API Test Automation for Beginners” emphasizes the importance of automated API tests in modern software development.

2. Types of API Testing

• The provided sources primarily focus on functional testing, which involves examining individual API endpoints to ensure they respond correctly to various HTTP requests and function as they should from a functional perspective.
• Other types of testing, such as performance tests and security tests, are mentioned but are outside the scope of the course.

3. The API Testing Process with Postman The process often begins with manual testing before moving to automation:

• Manual Testing: It is essential to understand how to manually test an API before automating it. This involves sending requests, inspecting status codes (e.g., expecting a 200 OK for success), and examining the response body to see if the data makes sense. For instance, checking if the API is “up and running” via a status endpoint is a foundational manual test.
• Transition to Automation: Manual checks are tedious and prone to human error when repeated multiple times. Automated API testing uses code to automatically check if all relevant criteria are fulfilled. This approach offers many benefits, including being faster, more accurate, and serving as documentation for expected API behavior.

4. Key Concepts and Tools in Postman for API Testing

Postman is a tool specifically designed to help with API testing and automation. Key features and concepts include:

• Postman Collections and Workspaces:
• A Postman Collection holds a group of API requests (e.g., for “Valentino’s Artisan Coffee House” API).
• A Postman Workspace is a central point for team collaboration, allowing users to see run results, write comments, and manage collections. Workspaces can be public or private.
• Forking a collection creates a copy, allowing users to make changes independently without affecting the original.
• Merging allows changes from a forked collection to be integrated back into the original, often via a pull request.
• Request Components and Interaction:
• HTTP Methods: Understanding methods like GET (for retrieving data) and POST (for creating data like an order or registering a client) is fundamental.
• Parameters: Requests can include query parameters (e.g., for pagination or filtering products by category) and path variables (e.g., for a single product ID).
• Request Body: POST requests typically have a request body where data to be sent to the API is specified, often in JSON format.
• Authentication: APIs often require authentication (e.g., an API key or token) to access certain endpoints, which should be handled securely. Postman’s “auth helper” can simplify this.
• Scripting in Postman (JavaScript):
• Postman tests are written using JavaScript.
• Pre-request Scripts execute before a request is sent.
• Tests (Post-response Scripts) execute after a response has been retrieved.
• The Postman Console is an essential debugging tool for viewing logs and request/response details chronologically.
• Variables:
• JavaScript Variables: Like containers that store data within a script, useful for temporary storage and manipulation. They have a defined scope, meaning where they are accessible (e.g., within a function or code block).
• Postman Variables: Allow information to be stored and passed between requests, persisting data long-term (e.g., base URL, API key, or data retrieved from one request for use in another). They can be collection, environment, or global variables.
• Random Postman Variables: Generate unique values (e.g., random names or emails) for testing various scenarios without hardcoding.
• Variables can be set directly from scripts (e.g., pm.collectionVariables.set()) and retrieved (pm.collectionVariables.get()).
• Data Types and Structures:
• JavaScript supports strings, numbers, booleans, objects, and arrays.
• Objects are used to group related properties (key-value pairs). Dot notation or square bracket notation can be used to access properties.
• Arrays store collections of elements, accessed by a zero-based index.
• undefined is a data type representing an uninitialized variable or a non-existent property.
• Functions and Callbacks:
• Functions are blocks of code designed to perform specific tasks, accepting arguments as input and optionally returning a value.
• Methods are functions defined within an object. The this keyword refers to the object itself within a method.
• Callback Functions are functions passed as arguments to other functions, allowing for flexible and efficient code execution. Postman’s pm.test method uses a callback function to encapsulate assertions.
• JSON and JSON Schema:
• JSON (JavaScript Object Notation) is a format used to send and retrieve data between machines, characterized by key-value pairs, double quotes for keys and string values, and curly braces for objects, and square brackets for arrays.
• Parsing JSON: The pm.response.json() method transforms a JSON string response into a JavaScript object that can be worked with in scripts.
• JSON Schema: A way to describe the structure and rules of JSON responses. It can validate if a JSON response follows an expected format, defining data types, required properties, and disallowing additional properties. Mock servers are invaluable for testing JSON schemas by simulating various response scenarios.
• Assertions:
• Assertions are used to check if an API response meets expected criteria.
• Postman primarily uses the Chai.js assertion library for readable assertions (e.g., pm.expect(value).to.equal(expected)).
• Assertions can check status codes (pm.response.to.have.status(200)), response body properties (existence, data type, value), and response headers (pm.response.headers.get(‘header-name’).to.equal(‘value’)).
• Regular Expressions can be used within assertions (e.g., to.match(regex)) to validate the format of data like IDs.

5. Automation and CI/CD Integration

• Postman Collection Runner: A tool within Postman that allows running an entire collection of requests with a single click, automating multiple tests and providing a report of passed/failed tests. It can be configured to run multiple iterations and persist response bodies for debugging.
• Scheduled Runs (Monitors): Collections can be scheduled to run automatically on the Postman cloud at predefined intervals (e.g., hourly, daily, weekly). This monitors the API’s health and sends notifications if issues arise, ideal for deployed APIs. Authentication issues in scheduled runs are often related to how API keys are stored (initial vs. current value).
• Postman CLI (Command Line Interface): A tool for running Postman collections from the command line, enabling integration with CI/CD pipelines and running tests on custom infrastructure without human intervention.
• CI/CD Integration: Postman API tests can be integrated into Continuous Integration and Continuous Deployment (CI/CD) pipelines (e.g., Jenkins, GitLab, GitHub Actions) using the Postman CLI. This automates testing every time software changes are made, catching problems early and ensuring continuous validation during development and deployment. Secure handling of API keys using environment variables or secrets in the CI/CD system is crucial.

By understanding these concepts and tools, developers and testers can effectively use Postman for robust API testing and automation.

Postman API Test Automation Handbook

Postman automation is a key aspect of modern API testing, allowing users to move beyond manual checks to automatically validate API functionality, reliability, performance, and security. It significantly enhances the efficiency and accuracy of the testing process.

Here’s a detailed discussion of Postman automation:

1. Importance and Transition to Automation

• Automated API tests are considered crucial in modern software development.
• While manual testing is essential for understanding an API, repeating these checks manually is tedious and prone to human error.
• Postman allows users to write a “tiny bit of code” that automatically verifies if all relevant criteria are met, transforming a basic form of testing into a robust automated process.
• Automated testing with Postman is faster and more accurate, as computers can execute tests repeatedly without making mistakes. It also serves as documentation for expected API behavior.

2. Key Postman Tools for Automation

Postman provides powerful tools that turn users into “API testing rockstars” by automating collection runs.

• Postman Collection Runner
• This tool allows users to run an entire collection of requests with a single click.
• It executes requests in the order they appear in the collection, though this order can be reconfigured.
• Users can choose to disable specific requests from the run (e.g., a “register new client” request).
• The runner provides a report of passed and failed tests, indicating the number of tests that passed or failed.
• For debugging, users can enable the “persist responses in a session” flag, which saves response bodies for review, helping to understand the reason for test failures.
• The “iterations” setting allows users to run the entire collection multiple times (e.g., 10 times) to catch intermittent issues, such as a bug that only occurs occasionally.
• Scheduled Runs (Monitors)
• This feature allows the execution of Postman collections on the Postman cloud, eliminating the need for the user’s computer to be on or Postman to be open.
• It enables fully automated collection runs at predefined intervals (e.g., hourly, daily, weekly).
• Scheduled runs are ideal for monitoring already deployed APIs to check if they are still working as expected, providing notifications if issues arise.
• Authentication issues in scheduled runs are often linked to how API keys are stored. The Postman cloud primarily accesses the initial value of collection variables, not the current value. Users must ensure sensitive information like API keys is correctly set in the initial value or managed securely, although making them public might not always be advisable.
• Results from scheduled runs are uploaded to the Postman cloud and can be viewed in detail within Postman, showing test pass/fail status and console logs.
• Postman CLI (Command Line Interface)
• The Postman CLI is a command-line tool that runs Postman collections.
• It is invaluable for streamlining the testing process, enabling full automation and easy integration with Continuous Integration/Continuous Deployment (CI/CD) pipelines.
• It allows Postman tests to be run on custom infrastructure without relying on the Postman cloud.
• Key commands include postman login (for authentication with an API key) and postman collection run <collection_ID>.
• The CLI provides detailed reports on test execution.
• It allows for configuring runs with additional options, such as running only specific folders using the -i flag (e.g., postman collection run <collection_ID> -i “folder_name”).
• Results from CLI runs are also published to the Postman cloud, allowing users to view reports within the Postman interface.
• Errors like console.clear not being a function can occur with Postman CLI, requiring conditional execution in scripts (e.g., if (typeof console.clear === ‘function’) { console.clear(); }).

3. Integration with CI/CD Pipelines

• Integrating Postman API tests into CI/CD pipelines (such as Jenkins, GitLab, Circle CI, GitHub Actions) is essential for continuous validation during development and deployment.
• It ensures that APIs are continuously validated and function as expected.
• Postman tests can be run at various stages, typically after deploying the API to a pre-production environment (e.g., test environment) and after deploying to the production environment.
• The Postman CLI is the tool used for this integration, allowing collections and their tests to be run without manual intervention.
• Secret management is critical: sensitive information like API keys should never be hardcoded directly into pipeline configuration files. Instead, they should be stored securely as environment variables or secrets within the CI/CD system (e.g., GitHub repository secrets).
• Postman provides pre-configured commands for various CI/CD providers (Bitbucket Pipelines, Jenkins, GitLab, Azure Pipelines, Travis CI), simplifying the setup process.

4. Foundational Concepts for Automation Effective automation in Postman relies on several core concepts:

• Postman Variables: Used to store and pass data between requests, and persist settings like base URLs or API keys. Random Postman variables can generate unique values for testing. Variables can be set directly from scripts (pm.collectionVariables.set()) and retrieved (pm.collectionVariables.get()).
• JavaScript Scripting: Tests are written in JavaScript, executed either before a request (pre-request scripts) or after receiving a response (tests/post-response scripts). The Postman Console is crucial for debugging scripts.
• Assertions: Postman primarily uses the Chai.js assertion library to check if API responses meet expected criteria. Assertions can validate status codes, response headers, and response body properties (e.g., value, data type, existence of properties, matching regular expressions).
• JSON Schema Validation: For complex responses, JSON schemas can be used to describe the expected structure and rules of JSON data, allowing for validation of the response body against a predefined schema. Mock servers are highly valuable for testing JSON schemas by simulating various response scenarios, helping to ensure the schema itself correctly identifies issues like missing required properties or unexpected additional properties.

5. Collaboration and Workspaces

• Postman Workspaces serve as a central point for team collaboration, enabling members to see run results, write comments, and manage collections.
• Forking a collection creates a copy, allowing individual team members to work on changes independently.
• Merging changes back into the original collection (often via pull requests) helps integrate contributions and track modifications. This workflow ensures changes are reviewed and integrated effectively, supporting the overall automation strategy.

By leveraging these features and understanding the underlying concepts, Postman provides a comprehensive environment for automating API testing, from individual requests to entire CI/CD pipelines.

JavaScript Essentials for Postman Automation

JavaScript is the programming language exclusively supported by Postman for writing scripts that automate API tests. Understanding JavaScript basics is fundamental for anyone looking to effectively use Postman for automation.

Here’s a discussion of essential JavaScript concepts relevant to Postman:

1. Scripting in Postman

• In Postman, scripts can be written in two main places for each request:
• Pre-request scripts: Executed before the request is sent.
• Test scripts: Executed after the request has been sent and a response has been retrieved.
• The Postman Console (console.log()) is a crucial tool for debugging these scripts, allowing users to print messages and variable values to understand code execution. A common practice is to use console.clear() in a pre-request script to clear the console before each run, though this command might require conditional execution when using the Postman CLI.

2. JavaScript Variables

• Variables are like containers that store data for use and manipulation within a script.
• They are declared using keywords such as let or const.
• let: Used for variables whose values can be changed during script execution.
• const: Used for constants, whose values cannot be changed once defined. Attempting to reassign a const will result in an error.
• Variables are typically assigned values using the equal sign (=).
• Variable Scope: A variable’s scope defines where it is available.
• JavaScript variables are scoped only to the script where they are defined and are not persisted between separate script executions or across pre-request and test scripts.
• Variables defined within a code block (enclosed by curly braces {}) have a local scope and are not accessible outside that block. This is a common pitfall for beginners.

3. Data Types JavaScript has various data types to represent information. The most common ones encountered in Postman scripts include:

• Strings: Represent text and are enclosed in single or double quotes (e.g., “Jamie”, ‘hello’). Even numbers become strings if enclosed in quotes (e.g., “29”).
• Numbers: Represent numerical values (e.g., 20, 30, 29.65) and do not require quotes.
• Booleans: Represent a state of something (on/off, true/false). Values are true or false and do not require quotes.
• Undefined: A special data type that represents a variable that has been declared but not initialized with a value. Attempting to access an undefined property on an object will return undefined instead of throwing an error.
• Objects: Used to group related data (properties) under a single variable.
• Defined using curly braces {}.
• Properties within an object are stored as key-value pairs, separated by a colon (:).
• Accessing properties: Use dot notation (e.g., person.name) for simple property names. For properties with special characters or spaces, square bracket notation with the property name as a string is required (e.g., person[’email-address’]).
• Adding/Modifying properties: Properties can be added or modified after an object’s creation using either dot or bracket notation (e.g., person.email = “test@example.com”).
• Arrays: A data structure that stores a collection or list of elements.
• Defined using square brackets [].
• Elements are identified by an index, starting from 0 (zero-indexed). For example, hobbies accesses the second element.
• Arrays are technically a specialized form of JavaScript objects, which is why typeof an array returns ‘object’.

4. Functions

• A function is a block of code designed to perform a specific task. It promotes code organization and reusability.
• Definition: Functions are defined using the function keyword, followed by a name, parentheses for parameters, and a code block (curly braces) for the function’s body.
• Invocation (Calling): A function is executed by calling its name followed by parentheses (e.g., greet()).
• Parameters and Arguments: Functions can accept inputs through parameters defined in their signature. When the function is called, values passed to these parameters are called arguments. These parameters behave like local variables within the function’s scope.
• Return Statements: The return keyword specifies the value that a function should output. If no return statement is present, the function implicitly returns undefined.
• Methods: When a function is defined as a property of an object, it is called a method. Methods can access other properties of their parent object using the this keyword (e.g., this.firstName). console.log is an example of a method, where log is a method of the console object.
• Anonymous Functions: Functions that do not have a name. They are often stored in variables or passed directly as arguments to other functions.
• Callback Functions: Functions passed as arguments to other functions, to be executed later (often when an event occurs or an operation completes). Postman’s pm.test() function takes a callback function containing assertions.

5. JSON Parsing

• APIs often communicate using JSON (JavaScript Object Notation), which represents data in a key-value format similar to JavaScript objects, but with specific rules (e.g., keys must be double-quoted).
• Postman receives API responses as strings, which need to be parsed (transformed) into JavaScript objects before their properties can be accessed and used in scripts.
• The pm.response.json() method is used to parse the response body into a JavaScript object.

By mastering these JavaScript fundamentals, users can write robust and dynamic Postman tests, perform assertions on API responses, manage data flow between requests using Postman variables, and integrate their tests into CI/CD pipelines.

JSON Schema for API Response Validation

JSON Schema is a crucial tool for validating the structure and rules of API responses, especially when those responses are in JSON format. It is also written in JSON, and it helps ensure that the data you receive from an API follows the expected format.

Here’s a detailed discussion of JSON Schema:

1. Purpose and Definition

• JSON Schema is used to describe the structure and rules of responses when your APIs communicate using JSON.
• It helps you determine if the JSON data you are receiving actually adheres to the expected format, making it easier to catch errors.
• While an API response might look fine in Postman’s pretty view, the actual data is a string that needs to be parsed into a JavaScript object before its properties can be accessed or validated.

2. Structure and Key Properties A JSON Schema is itself an object and defines properties that specify the expected structure of your JSON data:

• type: This property defines the overall data type of the JSON response, often an object. It can also be array, string, number, boolean, or others, depending on what the top-level of your JSON represents.
• properties: If the top-level type is an object, the properties keyword is used to define the expected key-value pairs within that object. Each property itself can have a type (e.g., string, integer, array) and other validation keywords.
• required: This is an array of strings listing the names of properties that must be present in the JSON response. If a required property is missing, the schema validation will fail.
• additionalProperties: By default, JSON Schema allows for any additional properties not explicitly mentioned in the schema to be present without causing validation to fail. Setting additionalProperties to false (e.g., additionalProperties: false) explicitly disallows any properties not defined in the schema. This is useful for ensuring that unexpected new fields in the API response are flagged, alerting you to changes.

3. Advanced Validation with JSON Schema

• pattern: For string types, you can define a pattern using regular expressions to validate the format of the string (e.g., ensuring an ID consists only of uppercase letters and numbers and has a fixed length).
• format: This keyword can be used with string types to specify expected data formats like date-time. If the string does not match the specified format, the validation will fail.
• Nested Structures: JSON Schema can define complex nested structures, such as an array of objects, where each object in the array must conform to its own schema (e.g., an array of products, where each product object must have ID and quantity properties).

4. Using JSON Schema in Postman Tests

• In Postman’s test scripts (executed after the request and response), you can write assertions to validate the response against a JSON Schema.
• The pm.response.to.haveJsonSchema() method is used for this, taking your defined schema as an argument.
• Before validating with a schema, it’s a good practice to first parse the response body into a JavaScript object using pm.response.json(). Also, validating that the response body is Json is a common first test for API responses.
• JSON Schemas are typically defined as a const variable within the test script.

5. Testing JSON Schemas with Mock Servers

• It is crucial to ensure that your JSON Schema actually fails when it should. A schema that never fails, even when the response deviates, provides a false sense of security.
• Postman Mock Servers are invaluable for testing your JSON schemas.
• A mock server creates a fake version of your actual API, providing responses without performing real processing or validation.
• This allows you to manipulate the mock response body (by saving an example response and then modifying it) to deliberately introduce errors or missing properties, and then verify that your schema catches these issues. This is especially useful when you cannot easily modify the real API’s responses.
• To create a mock, you save an example response from a request, then create a mock collection based on that example. The mock server’s URL can be saved as an environment variable to easily switch between the real API and the mock.

6. Pitfalls and Best Practices

• Avoid Schema Generators: Do not solely rely on websites that generate schemas from given responses, as these often produce schemas that are not robust or easily understandable.
• Understand Your Schema: Always take the time to learn about JSON schemas step-by-step and write them yourself to fully understand what is being tested.
• Test for Failure: Always test if your schema will fail when necessary. This means intentionally breaking the response (e.g., via a mock server) to ensure the schema catches the error.
• Specificity: While JSON Schema can be highly specific, consider if it makes sense to hardcode every value. Sometimes, checking data types or existence of properties is more appropriate than asserting specific values, especially for dynamic data.
• External Library: Postman’s assertion syntax, including to.haveJsonSchema(), is powered by the Chai JS assertion library, which offers many options for sophisticated tests.

Postman Variables: Powering API Automation

Postman variables are powerful tools that allow you to store and manipulate data within your Postman environment, streamlining your API testing and automation workflows. They are distinct from JavaScript variables, which are temporary and scoped only to the script where they are defined.

Here’s a discussion of Postman variables:

What are Postman Variables?

Variables in Postman are like containers that store data, enabling you to reuse values, manage dynamic data, and securely handle sensitive information across your requests and scripts. Unlike JavaScript variables, Postman variables persist between requests and can store settings and data long-term, such as a base URL or an API key.

Types of Postman Variables

1. Collection Variables:

• Scope: These variables are scoped to an entire Postman Collection, meaning they can be accessed by any request within that collection. This is ideal for values that are common to all requests in a collection, such as an API key or a specific product ID.
• Setting: You can set collection variables manually by editing the collection details under the ‘Variables’ tab.
• Current vs. Initial Value: When defining a collection variable, you’ll see “Initial Value” and “Current Value”.
• Initial Value is what is shared with others in a public workspace.
• Current Value is the one actively used by Postman when running requests on your machine. This distinction is crucial for handling secrets like API keys: storing them as a current value prevents them from being exposed in public workspaces, while still allowing you to use them in your requests. For Postman Cloud runs (like scheduled runs), the Postman cloud typically only has access to the initial value, which means you might need to move your secret to the initial value for cloud-based automation, with caution.
• Example: An API key or a product ID that you want to reuse across multiple requests within a collection.

1. Environment Variables:

• While not explicitly detailed as a separate type in the provided text, the source mentions that a mock server’s URL can be saved as an environment variable. This implies that environment variables can be used to store configuration details that might change between different environments (e.g., development, testing, production, or mock servers). When an environment is selected, its variables can override collection variables of the same name.

1. Random Postman Variables:

• These are dynamically generated values provided by Postman for testing various scenarios without hardcoding specific data.
• Syntax: They use a specific syntax like {{$randomFullName}} or {{$randomEmail}} within the request builder.
• Use Cases: Useful for generating unique customer names or emails for new registrations or orders.
• Important Note: Each time a random Postman variable is invoked, a new value is generated. This means if you use {{$randomFullName}} in the request body and then try to assert its value in the test script using the same syntax, they might differ because two separate generations occurred. To work around this, you can generate the value once in a pre-request script and store it in a Postman variable, then use that variable in both the request body and the test script.

Setting and Getting Postman Variables

• Using Variables in Request Builder: You can reference Postman variables in your request URLs, headers, or bodies by enclosing their names in double curly braces (e.g., {{productID}}). Postman automatically replaces these placeholders with their current values before sending the request.
• Setting Variables from Scripts:
• You can dynamically update or create Postman variables from your pre-request scripts or test scripts.
• The pm.collectionVariables.set(“variableName”, value) method is used to set or update a collection variable. This is particularly useful for extracting data from a response and passing it to subsequent requests, such as capturing a newly created orderID and using it to retrieve that order.
• Getting Variables from Scripts:
• To access the value of a Postman variable within a script, you use pm.collectionVariables.get(“variableName”).
• It’s important to remember that the {{variableName}} syntax does not work inside scripts; it’s only for the request builder.
• For random Postman variables accessed within scripts, pm.variables.replaceIn(“{{$randomFullName}}”) can be used to get the generated value.

Importance in API Test Automation

• Eliminating Manual Data Transfer: Postman variables are crucial for avoiding the manual copy-pasting of data between requests. For instance, an orderID generated by one API call can be automatically captured and used in a subsequent call to retrieve that specific order, significantly automating the workflow.
• Managing Dynamic Values: APIs often return dynamic data (e.g., unique IDs, timestamps). Variables allow you to capture and use these values in your tests without hardcoding, making your tests more robust and adaptable.
• Handling Authentication: API keys and tokens can be stored as collection variables, making it easy to manage authentication across multiple requests without embedding credentials directly in each request.
• Configuring Environments: Variables, especially environment variables, allow you to easily switch between different API environments (e.g., development, staging, production, or mock servers) by changing a single variable value.
• Debugging: By logging variable values to the Postman Console, you can inspect the data flow and troubleshoot your scripts effectively.

In essence, Postman variables are fundamental for building flexible, robust, and automated API tests, allowing for efficient management of data and secrets throughout your Postman collections.

By Amjad Izhar
Contact: amjad.izhar@gmail.com
https://amjadizhar.blog

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This comprehensive guide introduces Postman as a vital tool for API testing, explaining its utility in interacting with web-based APIs and automating test processes. It details fundamental API concepts, including HTTP methods (GET, POST, PATCH, DELETE), request/response structures, and status codes. The resource demonstrates practical Postman features such as collections, variables (global, collection, environment), and scripting for automated tests using JavaScript, emphasizing assertions and dynamic data handling. Finally, it explores Postman’s Collection Runner for sequential test execution and Newman for command-line automation and report generation, showcasing how these tools integrate into continuous integration pipelines for robust API validation.

Postman API Testing: Concepts, Automation, and Limitations

API testing involves interacting with APIs to ensure they work as expected. Instead of verifying the API manually, the goal is to automate this process by writing API tests, allowing Postman to perform the checks and only requiring human intervention if something goes wrong. The source specifically focuses on using Postman for web-based API testing, where APIs work over the internet, exchanging data rather than electricity through a server interface.

Key Concepts in API Testing with Postman:

• APIs as Interfaces/Contracts: An API is an interface to a server that provides data or performs actions. To use an API, you need to know and follow its specifications, much like a power outlet requires a specific plug.
• Postman as a Tool: Postman simplifies connecting to APIs and making the process of sending and receiving data easier. It allows users to configure various aspects of an HTTP request and view the corresponding response.
• HTTP Messages: Communication between a client (e.g., Postman) and a server (the API) uses HTTP messages.
• Request: The message sent from Postman to the API. It contains:
• URL/Address: The location where the request is sent, consisting of a base URL and specific endpoints.
• Request Method (HTTP Verbs): Indicates the intended action. Common methods include:
• GET: Used to retrieve data.
• POST: Used to send data to create a new resource, like ordering a book or registering an API client.
• PATCH: Used to update existing data, such as changing a customer name for an order.
• DELETE: Used to remove a resource, like deleting an order.
• Headers: Provide meta-information about the message, such as Content-Type (e.g., application/json) or User-Agent. They are often used for authentication.
• Body: Contains the data being sent with the request, typically used with POST and PATCH methods, often in JSON format.
• Response: The message coming back from the API. It contains:
• Status Code: A numerical code indicating the outcome of the request.
• 2xx (Success):200 OK: Request was understood, and everything was fine.
• 201 Created: A resource was successfully created.
• 204 No Content: The request was successful, but there is no content to return in the response body.
• 4xx (Client Error): Indicates an issue with the request sent by the client.
• 400 Bad Request: The API understood the request, but what was sent was incorrect or invalid (e.g., invalid query parameter value, missing body property).
• 401 Unauthorized: Missing authorization header, indicating that authentication is required.
• 404 Not Found: The requested resource (e.g., book ID, order ID, or endpoint) does not exist.
• 409 Conflict: The request could not be processed because of a conflict (e.g., API client already registered).
• 5xx (Server Error): Typically indicates a server issue.
• Headers: Additional meta-information about the response.
• Response Body: The most important part, containing the actual data or information requested from the server.
• Endpoints: Specific addresses within an API that offer different responses or functionalities (e.g., /status, /books, /orders).
• Parameters:Query Parameters: Optional or mandatory additional data sent with a request, appearing after a question mark (?) in the URL as key-value pairs separated by & (e.g., ?type=fiction&limit=2). Their behavior is defined in the API documentation.
• Path Parameters (Path Variables): Values embedded directly in the URL path, representing a specific resource (e.g., /books/{bookId}). They change dynamically and do not use a question mark.
• Authentication: Many API endpoints, especially those that create or modify data, require authentication. This often involves registering an API client to obtain an access token, which acts like a temporary password and is typically sent in an Authorization header with subsequent requests.
• JSON (JavaScript Object Notation): A common data format for sending and receiving data with APIs due to its portability and ease of parsing in programming languages. It uses key-value pairs, where keys are strings in double quotes, and values can be strings, numbers, booleans, objects, or arrays.

Writing API Tests in Postman:

1. Tests Tab: Postman allows users to write tests in the “Tests” tab of a request using JavaScript code.
2. Assertions: Tests typically involve assertions, which check if the response meets specific expectations.

• Status Code Test: The most common test is to verify the HTTP status code (e.g., pm.response.to.have.status(200)).
• Response Body Tests:Parsing JSON: The raw JSON response needs to be parsed into a JavaScript object using pm.response.json() before its properties can be accessed and tested.
• Checking Property Values: Assertions can verify specific values or properties within the parsed response body (e.g., pm.expect(response.status).to.equal(‘okay’)).
• Checking Conditions: Tests can also check if numerical values are above a certain threshold (e.g., pm.expect(response[‘current-stock’]).to.be.above(0)).

1. Debugging with Postman Console: The Postman Console is a crucial tool for debugging. It logs requests and responses and can be used to console.log() variable values or parsed responses during test execution to understand what data is being processed.

Automating API Tests:

To move beyond manual testing, Postman offers several automation features:

• Variables: Using variables helps avoid hardcoding data and makes tests more dynamic and reusable.
• Collection Variables: Saved within a specific collection and accessible to all requests within it (e.g., base_url).
• Global Variables: Available across the entire Postman workspace for all collections.
• Environment Variables: Useful for different environments (e.g., local, testing, production), allowing easy switching of configurations like base URLs.
• Random Variables: Postman provides special variables (e.g., $randomFullName, $randomLastName) to generate random data for requests, useful for diverse test data.
• Dynamic Variable Setting: Variables (like orderId or bookId) can be set programmatically within tests from the response body of one request, then used in subsequent requests, eliminating manual copy-pasting.
• Collection Runner: A built-in Postman tool that allows you to execute an entire collection of requests with one click. You can define the run order of requests, save responses for review, and enable/disable specific requests.
• Monitors: Postman monitors allow you to schedule collections to run automatically on Postman’s cloud infrastructure at defined frequencies (e.g., daily, hourly). They send notifications (e.g., by email) if tests fail, providing a way to continuously check API health without keeping Postman open locally. Debugging can be more challenging here compared to local runs.
• Newman: A command-line interface (CLI) tool for Postman collections. Newman allows you to run Postman collections and their tests from the command line, making it ideal for integration into Continuous Integration/Continuous Deployment (CI/CD) pipelines (e.g., Jenkins, GitLab CI, TeamCity, CircleCI).
• Exporting Collections: Collections can be exported as JSON files or accessed via public links/Postman API for use with Newman.
• Reporting: Newman can generate various reports, including the highly useful HTML Extra report, which provides a detailed, visual overview of all requests, responses, headers, and test results, aiding significantly in debugging.

What Postman is NOT Designed For:

Postman is primarily for API interaction and testing, but it has limitations:

• User Interaction Testing: It is not for testing user interfaces, forms, or button clicks on websites.
• Performance Testing: It is not designed for sending a large volume of requests in a short time frame for performance testing.
• Primary Security Testing: While it can be used, it’s not its primary focus, and other tools are better suited for comprehensive security testing.

Overall, API testing with Postman involves understanding API structure, crafting requests, analyzing responses, writing automated tests using JavaScript, and then automating these tests through features like the Collection Runner, Monitors, or Newman for continuous integration.

Postman: A Comprehensive Guide to API Interaction and Testing

Postman is a tool designed for interacting with web-based APIs, meaning APIs that operate over the internet. It acts as an interface to a server, allowing users to send data and receive responses easily. The primary purpose of Postman is to simplify the process of connecting to APIs and to facilitate the sending and receiving of data.

Key Functionalities and Features of Postman:

• API Interaction: Postman enables you to configure various aspects of an HTTP request and view the corresponding response. This includes setting the URL, choosing the request method (like GET, POST, PATCH, DELETE), defining headers, and adding a request body.
• Request and Response Handling:Requests: In Postman, you can build HTTP requests by specifying the URL (which combines a base URL and an endpoint), the HTTP method (also known as HTTP verb), headers for meta-information (e.g., Content-Type, User-Agent, Authorization), and a body for sending data (typically with POST or PATCH requests).
• Responses: Postman displays the API’s response, which includes the status code (e.g., 200 OK, 201 Created, 400 Bad Request, 401 Unauthorized, 404 Not Found, 409 Conflict, 5xx Server Error), response headers, and the response body, which contains the actual data from the server. Data is often formatted in JSON.
• Organizing Work with Collections: Postman allows you to organize multiple requests into collections, typically for the same API or related use cases. This helps in managing and reusing requests.
• Variables: To avoid hardcoding values and make requests more dynamic and reusable, Postman supports various types of variables:
• Collection Variables: Saved within a collection and accessible by all requests in that collection (e.g., base_url).
• Global Variables: Available across the entire Postman workspace for all collections.
• Environment Variables: Useful for different deployment environments (e.g., local, testing, production), allowing easy switching of configurations like base URLs.
• Random Variables: Postman provides special variables (e.g., $randomFullName, $randomLastName) to generate random data for requests, useful for diverse test data.
• Dynamic Variable Setting: Crucially for automation, Postman allows you to programmatically extract data from a response and set it as a variable for use in subsequent requests, eliminating manual copy-pasting (e.g., setting an orderId after an order is created).
• API Authentication: Postman simplifies handling authentication by allowing users to register API clients to obtain access tokens (temporary passwords). These tokens are then typically included in an Authorization header for subsequent requests, often using an “Authorization helper” like “Bearer Token” to auto-generate the header.
• API Testing Capabilities: Postman is central to API testing by enabling users to:
• Write Tests: Users can write JavaScript code in the “Tests” tab of a request to define assertions.
• Use Code Snippets: Postman provides built-in code snippets to quickly generate common tests, such as verifying the status code (pm.response.to.have.status(200)) or parsing JSON responses.
• Assertions: Tests involve asserting expectations against the API’s response, like checking specific property values in the JSON body (pm.expect(response.status).to.equal(‘okay’)) or numerical conditions (pm.expect(response[‘current-stock’]).to.be.above(0)).
• Debugging: The Postman Console is a vital debugging tool, logging requests and responses and allowing console.log() statements to inspect variable values or parsed responses during test execution.

Automation of API Testing with Postman:

Postman offers several ways to automate the API testing process, moving beyond manual execution:

• Collection Runner: A built-in feature that allows you to execute an entire collection of requests with one click. You can define the run order, enable/disable requests, and save responses for review. It can also use postman.setNextRequest() to control the flow of execution within a collection.
• Monitors: Postman Monitors enable scheduling collections to run automatically on Postman’s cloud infrastructure at specified frequencies (e.g., daily, hourly). They can send notifications (e.g., by email) if tests fail, providing continuous API health checks. Note that debugging can be more challenging here compared to local runs.
• Newman: A command-line interface (CLI) tool for Postman collections. Newman allows you to run Postman collections and their tests from the command line, making it ideal for integration into Continuous Integration/Continuous Deployment (CI/CD) pipelines (e.g., Jenkins, GitLab CI, TeamCity, CircleCI). Collections can be exported as JSON files or accessed via public links for use with Newman. Newman also supports various reporting options, including the valuable HTML Extra report, which provides a detailed, visual overview of requests, responses, and test results for debugging.

What Postman is NOT Designed For:

While powerful for API testing, Postman has specific limitations:

• User Interaction Testing: It is not for testing user interfaces, forms, or button clicks on websites.
• Performance Testing: It is not designed for sending a large volume of requests in a short time frame for performance testing.
• Primary Security Testing: While it can be used for some security checks, it is not its primary focus, and other specialized tools are better suited for comprehensive security testing.

Mastering HTTP Requests in Postman

HTTP requests are fundamental to how Postman interacts with web-based APIs. In a client-server communication model, an HTTP request is the message sent from the client (e.g., Postman) to the server or API. The server then sends back an HTTP response.

Postman allows you to configure many aspects of an HTTP request, enabling users to easily send data and receive responses.

Components of an HTTP Request:

1. URL (Uniform Resource Locator): This is the address where the request is sent. It often consists of a base URL and an endpoint.

• Base URL: The main address of the API (e.g., https://simple-books-api.com). Postman allows you to save this as a variable (e.g., base_url) to avoid hardcoding and make requests more reusable.
• Endpoints: Specific paths that offer different kinds of responses or functionalities within an API (e.g., /status, /books, /orders).

1. Request Method (HTTP Verb): This specifies the action you want to perform on the server. Postman provides a dropdown to select the method.

• GET: Used to retrieve data from the server. It typically does not include a request body.
• POST: Used to send data to the server to create a new resource (e.g., to order a book, register an API client). This method requires a request body.
• PATCH: Used to update an existing resource on the server by sending only the changed data. This method also allows for a request body.
• DELETE: Used to remove a resource from the server. It typically does not require a request body, only the identifier of the resource to be deleted.

1. Headers: These are like meta-information or additional information that travels with the request. Postman automatically adds some headers, such as User-Agent.

• Content-Type: A common header that tells the server the format of the request body (e.g., application/json).
• Authorization: A crucial header for authentication, used to send access tokens or other credentials to private API endpoints. Postman provides an “Authorization helper” (e.g., “Bearer Token”) to auto-generate this header correctly.

1. Request Body: This is where you send the actual data to the server, typically with POST or PATCH requests.

• The body is often formatted as JSON (JavaScript Object Notation), which is a key-value way of sending data. Postman helps ensure JSON validity, warning you if it’s malformed.
• Data types within JSON (e.g., strings in double quotes, numbers without quotes, booleans) are important for valid JSON.

Parameters in Requests:

HTTP requests can include parameters to filter, limit, or identify resources.

• Query Parameters:Additional data submitted with the request, found in the URL after a question mark (?).
• They are structured as key-value pairs (e.g., type=fiction, limit=2).
• Multiple query parameters are separated by an ampersand (&).
• Their availability and expected values are defined in the API documentation. If an incorrect value is sent, the API may return a 400 Bad Request status code with an informative error message in the response body.
• Path Parameters (or Path Variables):Part of the URL path itself, used to specify a value for a variable within the path (e.g., /books/{bookId}).
• Unlike query parameters, they do not involve a question mark and the key (e.g., bookId) is not sent, only its value.
• Postman displays them nicely in the editor, making it easier to see and change the values (e.g., changing bookId from 1 to 2).

Request Outcomes (Status Codes in Response):

While status codes are part of the response, they directly indicate the outcome of the request:

• 2xx (Success): Indicates the request was understood and processed successfully.
• 200 OK: General success.
• 201 Created: A new resource was successfully created as a result of the request.
• 204 No Content: The request was successful, but there is no content to return in the response body (e.g., for successful PATCH or DELETE requests).
• 4xx (Client Error): Indicates that something was wrong with the request sent by the client.
• 400 Bad Request: The API understood the request, but the data sent was incorrect or invalid (e.g., invalid query parameter value, invalid request body).
• 401 Unauthorized: The request requires authentication, but no valid authorization credentials were provided.
• 404 Not Found: The requested resource does not exist (e.g., trying to get a book with a non-existent ID, trying to order an out-of-stock book).
• 409 Conflict: The request could not be completed due to a conflict with the current state of the resource (e.g., trying to register an API client that’s already registered).
• 5xx (Server Error): Indicates an issue on the server side.

Automating Requests with Postman:

Postman facilitates the automation of sending requests and managing their data:

• Variables: Requests can use collection, global, or environment variables to store values like base_url or access_token, making requests reusable and adaptable across different scenarios or environments.
• Dynamic Variable Setting: Postman tests can extract data from a response body and set it as a variable for subsequent requests. This avoids manual copy-pasting and enables chained requests (e.g., creating an order and then using the returned orderId to get or delete that specific order).
• Random Variables: Special variables (e.g., $randomFullName) can be used in request bodies to generate random data, useful for testing with diverse inputs.
• Postman Console: This debugging tool logs the full request and response, including headers and body, which is crucial for understanding what was sent and received, especially when issues arise.

Postman: Mastering API Test Automation

Test automation in Postman transforms the manual process of verifying API functionality into an efficient, repeatable, and less time-consuming operation. Instead of manually inspecting API responses, Postman can be configured to automatically check if the API behaves as expected.

Why Automate API Testing with Postman?

• Reduced Manual Effort: Automating tests means you no longer have to retest everything manually when an API changes, which saves a significant amount of time.
• Eliminate Manual Copy-Pasting: Automation avoids the need to manually copy data (like an orderId or access_token) from one request’s response to another request’s body or URL.
• Proactive Issue Detection: Postman can be set up to perform continuous checks, notifying you if something goes wrong with the API.

Key Components Enabling Automation

1. Writing API Tests:

• JavaScript Code: Postman allows you to write JavaScript code in the “Tests” tab of a request. This code executes after the API receives a response.
• Assertions: Tests involve assertions, which are statements that check if the API response meets certain expectations. For example, pm.response.to.have.status(200) checks if the status code is 200.
• Code Snippets: Postman offers built-in code snippets to quickly generate common tests, making it easier for beginners.
• Parsing JSON Responses: Since API response bodies are often in JSON format, tests commonly involve parsing the JSON response into a JavaScript object (e.g., pm.response.json()) to access specific data points for assertions.
• Debugging with Postman Console: The Postman Console is a crucial tool for debugging. It logs requests and responses, and console.log() statements can be used within tests to inspect variable values or parsed JSON objects, helping in understanding what data is available for testing.

1. Using Variables for Dynamic Data:

• Variable Scopes: Postman supports different variable scopes:
• Collection Variables: Saved within a collection and accessible by all requests in that collection (e.g., base_url).
• Global Variables: Available across the entire Postman workspace, accessible by all collections.
• Environment Variables: Useful for different deployment environments (e.g., local, testing, production).
• Dynamic Variable Setting: A powerful automation feature is the ability to programmatically extract data from a response and set it as a variable for subsequent requests. For example, after creating an order, the orderId from the response can be stored in a global variable and then used in “Get an Order” or “Delete Order” requests, eliminating manual copy-pasting.
• Random Variables: Postman provides special random variables (e.g., $randomFullName, $randomLastName) that can be used in request bodies to generate diverse test data without manual input.

Postman’s Automation Tools

1. Collection Runner:

• A built-in Postman tool that allows you to execute an entire collection of requests with a single click.
• You can define the run order of requests, enable or disable specific requests, and choose to save responses for review and debugging.
• It offers a visual report of test successes and failures.
• The postman.setNextRequest() function can be used in tests to control the flow of execution within a collection, allowing you to skip requests or create conditional workflows.

1. Monitors:

• Postman Monitors enable you to schedule collections to run automatically on Postman’s cloud infrastructure at specified frequencies (e.g., daily, hourly).
• They can send notifications (e.g., by email) if tests fail, providing continuous API health checks even when Postman is not open.
• Debugging issues that occur in monitors can be more challenging compared to local runs, often due to missing or improperly set variables (especially if not defined in the “initial value” when sharing collections).

1. Newman:

• Newman is a command-line interface (CLI) tool for Postman collections.
• It allows you to run Postman collections and their associated tests from the command line, making it ideal for integration into Continuous Integration/Continuous Deployment (CI/CD) pipelines like Jenkins, GitLab CI, TeamCity, or CircleCI.
• Exporting Collections: Collections can be exported as JSON files or accessed via public links for use with Newman.
• Reporting: Newman supports various reporting options, with the HTML Extra report being particularly valuable. This report provides a detailed, visual overview of requests, responses, and test results, crucial for debugging in an automated pipeline. It includes full request and response logs.

By leveraging these features, Postman enables comprehensive API test automation, ensuring the reliability and functionality of web-based APIs within development and deployment workflows.

Newman: Postman Collection Automation for CI/CD Pipelines

Newman is a command-line interface (CLI) tool for Postman collections. It allows you to run Postman collections and their associated tests directly from the command line, making it an essential tool for integrating API tests into Continuous Integration/Continuous Deployment (CI/CD) pipelines.

Key Aspects of Newman CLI:

• Purpose and Benefits:
• Automated Execution: Newman automates the execution of your Postman collections, eliminating the need to manually click through requests in the Postman application.
• CI/CD Integration: It is designed for use in professional build and testing servers like Jenkins, GitLab CI, TeamCity, or CircleCI. This means you can automatically run your API tests as part of your software build and deployment process.
• Proactive Issue Detection: Newman helps ensure the API is working properly after deployment, notifying you if tests fail within the pipeline.
• Prerequisites:
• To use Newman locally on your computer, you need to have Node.js installed.
• Accessing Postman Collections for Newman: There are multiple ways to provide your Postman collection to Newman for execution:
• Export as JSON File: You can export your collection as a JSON file from Postman.
• Public Link: Postman allows you to generate a public link for your collection. However, remember to update the link manually in Postman every time you make changes to the collection for Newman to pick them up.
• Postman API: It’s also possible to access collections via the Postman API using an API key.
• Running Collections with Newman:
• The basic command to run a collection is newman run [collection_path_or_link].
• Newman can run collections supplied either as a local JSON file or via a public HTTP link.
• Potential Failures: Runs might fail due to missing Postman variables or tokens that were not set as initial values or were only available as global variables and not properly exported (e.g., if environments are not exported along with the collection).
• Reporting with Newman:
• Importance of Reports: Generating reports is crucial for debugging and understanding what happened during the test run, especially in an automated pipeline where you don’t have direct access to the Postman GUI.
• HTML Extra Report: The HTML Extra report is highly favored in the Postman community.
• It provides a detailed, visual overview of what has happened, including requests and responses.
• It contains full request and response logs, which are extremely helpful for debugging issues.
• You can specify multiple reporters (e.g., cli and htmlextra) using the –reporters flag.
• Integration into CI/CD Pipelines:
• In a typical CI/CD pipeline, after an API’s code is compiled and deployed to a server, Newman is used to run API tests.
• The results of these tests, including detailed reports from HTML Extra, can then be reviewed within the pipeline’s interface (e.g., in GitLab CI, Jenkins) to determine the success or failure of the deployment.
• Newman allows you to specify environments and other configurations when running tests in a pipeline.
• Debugging with Newman:
• The rich data in Newman reports (like full request headers, request bodies, and response bodies) is invaluable for debugging when tests fail in an automated context. If a Postman variable wasn’t resolved, for example, the report will show it, indicating a potential configuration issue.

By Amjad Izhar
Contact: amjad.izhar@gmail.com
https://amjadizhar.blog

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