11.4.1 - Common Assertions

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Introduction to Assertions

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Teacher
Teacher

Welcome, class! Today, we will be discussing assertions and how they help in validating API responses. Can anyone tell me what they think an assertion is?

Student 1
Student 1

I think it's something to check if the response from the API is correct?

Teacher
Teacher

Exactly, Student_1! Assertions are statements that validate whether the actual outcome matches the expected outcome. They are crucial in ensuring our APIs behave as intended.

Student 2
Student 2

What kind of things can we check with assertions?

Teacher
Teacher

Great question! We can check for things like status codes, specific fields in the response, and their values. For example, we can assert that the status code we expect is 200, indicating a successful response.

Student 3
Student 3

So, verifying that we receive '200 OK' is a common assertion, right?

Teacher
Teacher

That's right! It's fundamental. Let's remember it with the acronym 'COV' - Correct Outcome Validation. By focusing on these validations, we ensure our APIs are reliable.

Teacher
Teacher

To summarize, assertions are key for validating API responses. We can check status codes and expected fields in the JSON response to make sure everything works as it should.

Writing Assertions in Postman

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Teacher
Teacher

Now that we understand what assertions are, let's talk about how to write them in Postman. Who remembers where we can write these assertions?

Student 1
Student 1

Is it in the 'Tests' tab after sending a request?

Teacher
Teacher

Correct, Student_1! The 'Tests' tab is where we write our JavaScript code to validate responses. Let's look at a simple assertion.

Student 2
Student 2

What would be an example of such an assertion?

Teacher
Teacher

Let's say we want to test if the response has a specific user name. We could write it like this: `pm.test('Response has user name', function() { var jsonData = pm.response.json(); pm.expect(jsonData.name).to.eql('Charlie'); });`

Student 4
Student 4

How does that work?

Teacher
Teacher

Good question, Student_4! In this code, we check if the 'name' field in our JSON response equals 'Charlie'. If it does, our test passes; if not, it fails.

Teacher
Teacher

Remember to use 'JSON' for parsing. To summarize, assertions in Postman can validate fields in API responses, ensuring our applications work as intended!

Introduction & Overview

Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.

Quick Overview

This section introduces common assertions used in API testing with Postman, emphasizing their significance in validating responses.

Standard

It covers key components of API testing using Postman's capabilities, detailing how to write assertions to check response status, fields, and values. The section highlights practical examples to illustrate how these assertions function in ensuring API reliability.

Detailed

Detailed Summary

In this section, we focus on the significance of assertions in API testing using Postman. Assertions are crucial for validating the responses received from APIs to ensure that the application behaves as expected. The ability to write assertions allows QA professionals to automate tests effectively, reducing human error and increasing efficiency.

What are Assertions?

Assertions are statements written in JavaScript that test expected outcomes against actual outcomes. In Postman, assertions can be written in the Tests tab after sending a request. They can check various aspects such as the HTTP response status code, the presence of certain fields in the response body, and the correctness of the data types of those fields.

Common Assertions:

  1. Status Code Validation: Ensures that the API returns the correct HTTP status codes (like 200 for success).
    • Example: pm.test("Status code is 200", function () { pm.response.to.have.status(200); });
  2. Field Presence Validation: Validates that the expected fields are present in the response.
    • Example: pm.test("Response has user name", function () { var jsonData = pm.response.json(); pm.expect(jsonData.name).to.eql("Charlie"); });

Importance of Assertions

Assertions not only enhance the reliability of the API by confirming that the responses are correct but also allow for regression testing, where previous tests can be re-run to ensure new changes haven't adversely affected existing functionalities. They also provide clear feedback when tests fail, aiding in the quick identification and resolution of issues. Thus, mastering assertions is vital for effective API testing.

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Introduction to Assertions in Postman

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Postman allows you to write JavaScript-based tests under the Tests tab to automate validation of response data.

Detailed Explanation

In Postman, users can create automated tests to validate API responses. This is done in the 'Tests' tab, where you can write JavaScript code that checks various aspects of the response. This automation is crucial for ensuring that the API behaves as expected every time a request is made.

Examples & Analogies

Think of it like a teacher grading a stack of papers from students. Instead of checking each paper manually, they create a rubric (which is comparable to a test in Postman) to quickly check if students have followed the guidelines and performed well.

Writing Basic Assertions

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// Status code is 200
pm.test("Status code is 200", function () {
pm.response.to.have.status(200);
});

// Response contains expected field
pm.test("Response has user name", function () {
var jsonData = pm.response.json();
pm.expect(jsonData.name).to.eql("Charlie");
});

Detailed Explanation

This chunk showcases two examples of assertions written in Postman. The first checks if the API response status code is 200, meaning the request was successful. The second checks if the response contains a specific field ('name') and verifies that its value matches 'Charlie'. These checks ensure that the API is functioning correctly and returning the expected data.

Examples & Analogies

Consider a restaurant where you order food. The first assertion is like checking if the meal you ordered (status code 200) arrived on time. The second assertion is like verifying that the meal has the correct dish with your name written (the expected field) on it, ensuring you got exactly what you asked for.

Where to Add Assertions

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● After sending a request, go to the Tests tab
● Write or paste JavaScript code to check status, headers, body, etc.

Detailed Explanation

After you send an API request in Postman, you can navigate to the 'Tests' tab to add your assertions. This is where you can enter the JavaScript code to validate different parts of the response, such as status codes, response headers, and the body content. This step enhances the testing process by ensuring you can automatically verify the response structure and content.

Examples & Analogies

Imagine baking a cake and wanting to ensure it turns out right. After baking (sending the request), you would check various features like taste (body), appearance (headers), and texture (status codes) by having a checklist (your JavaScript assertions) to confirm that everything is in order.

Definitions & Key Concepts

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Key Concepts

  • Assertions: Statements that validate expected outcomes against actual API responses.

  • Status Codes: Numeric codes that indicate the result of HTTP requests.

  • Response Body: The main data returned by an API in response to a request.

  • JavaScript Testing: The use of JavaScript code to automate validation in Postman.

Examples & Real-Life Applications

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Examples

  • Example of a status code assertion: pm.test('Status code is 200', function() { pm.response.to.have.status(200); });

  • Example of field validation: pm.test('Response has user name', function() { pm.expect(jsonData.name).to.eql('Charlie'); });

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎵 Rhymes Time

  • API tests are never a bore, assertions help us check what's in store.

📖 Fascinating Stories

  • Once in a digital land, a developer used Postman to ensure her APIs worked well. Each time she sent a request, she wrote assertions to confirm that the responses were correct. It became a magical routine that kept everything reliable.

🧠 Other Memory Gems

  • For assertions, remember 'COV' for Correct Outcome Validation.

🎯 Super Acronyms

R.A.C.E. = Response Assertions Check Everything.

Flash Cards

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Glossary of Terms

Review the Definitions for terms.

  • Term: Assertion

    Definition:

    A statement in Postman that tests whether the actual outcome matches the expected outcome in API responses.

  • Term: Status Code

    Definition:

    A code sent by the server that indicates the outcome of the HTTP request (e.g., 200 for success, 404 for not found).

  • Term: Response Body

    Definition:

    The data returned by the API after a request is made, usually in JSON or XML format.

  • Term: JSON

    Definition:

    JavaScript Object Notation, a lightweight data exchange format that is easy for humans to read and write, and easy for machines to parse and generate.