Response body array assertions in Postman - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a response body array assertion in API testing?

It is a check to confirm that the response from an API contains an array and that this array meets certain conditions like length, content, or structure.

beginner

How do you check if the response body contains an array with at least 3 items in Postman?

Use the assertion: pm.expect(pm.response.json()).to.be.an('array').with.lengthOf.at.least(3);

intermediate

Why is it important to assert the type of response body elements in an array?

To ensure the API returns data in the expected format, which helps avoid errors in later processing or display of data.

intermediate

Show how to assert that every item in a response array has a property 'id' in Postman.

Use: pm.response.json().forEach(item => pm.expect(item).to.have.property('id'));

intermediate

What does the assertion pm.expect(pm.response.json()).to.include.members([1, 2]) check in a response array?

It checks that the response array includes the members 1 and 2 somewhere in its elements.

Which Postman assertion checks if the response body is an array?

A pm.expect(pm.response.code).to.equal(200);

B pm.expect(pm.response.text()).to.be.a('string');

C pm.expect(pm.response.json()).to.have.property('length');

D pm.expect(pm.response.json()).to.be.an('array');

Option D correctly checks that the response body parsed as JSON is an array.

How do you assert that every object in a response array has a 'name' property?

A pm.response.json().forEach(item => pm.expect(item).to.have.property('name'));

B pm.expect(pm.response.json()).to.include('name');

C pm.expect(pm.response.json()).to.have.property('name');

D pm.expect(pm.response.json()).to.be.an('array');

Option A loops through each item and asserts the 'name' property exists.

What does this assertion check? pm.expect(pm.response.json()).to.have.lengthOf(5);

A Response array has exactly 5 items.

B Response array has at least 5 items.

C Response array has no more than 5 items.

D Response array is empty.

It checks the array length is exactly 5.

Which assertion verifies that the response array includes the number 10?

A pm.expect(pm.response.json()).to.include(10);

B pm.expect(pm.response.json()).to.include.members([10]);

C pm.expect(pm.response.json()).to.have.property(10);

D pm.expect(pm.response.json()).to.be.an('array');

Option B checks that the array includes the member 10.

Why should you assert the response array structure in API testing?

A To speed up the API response time.

B To change the API response data.

C To confirm the API returns data in the expected format.

D To ignore errors in the response.

Asserting structure ensures data is correct and usable.

Explain how to write assertions in Postman to verify that a response body contains an array with specific properties in each item.

Think about using pm.response.json(), array methods, and pm.expect() assertions.

Describe why it is important to assert the length and content of an array in an API response.

Consider what happens if the array is empty or missing expected elements.

Practice

1. What does a response body array assertion in Postman primarily check?

easy

A. If the API returns a list of items as expected

B. If the API response time is under 1 second

C. If the API headers contain authentication tokens

D. If the API URL is correctly formatted

Solution

1. Step 1: Understand the purpose of response body array assertions

   These assertions verify the data returned by the API, especially when it should be a list or array of items.

2. Step 2: Identify what is checked in the response body

   We check if the response contains an array, its length, and the properties of each item to ensure data correctness.

3. Final Answer:

   If the API returns a list of items as expected -> Option A

4. Quick Check:

   Response body array assertions check list presence [OK]

Hint: Focus on verifying the list of items in the response body [OK]

Common Mistakes:

• Confusing response time with response content
• Checking headers instead of body data
• Assuming URL format is part of body assertions

2. Which of the following is the correct Postman test code to assert that the response body is an array?

easy

A. pm.test('Response is array', () => pm.expect(pm.response.json()).to.be.a('string'))

B. pm.test('Response is array', () => pm.expect(pm.response.text()).to.be.an('array'))

C. pm.test('Response is array', () => pm.expect(pm.response.json()).to.be.an('array'))

D. pm.test('Response is array', () => pm.expect(pm.response.body).to.be.an('object'))

Solution

1. Step 1: Identify the correct method to parse JSON response

   pm.response.json() parses the response body as JSON, which is needed to check if it is an array.

2. Step 2: Use the correct Chai assertion syntax

   to.be.an('array') correctly asserts the type is an array. Using pm.response.text() or wrong types will fail.

3. Final Answer:

   pm.test('Response is array', () => pm.expect(pm.response.json()).to.be.an('array')) -> Option C

4. Quick Check:

   Use pm.response.json() and to.be.an('array') [OK]

Hint: Use pm.response.json() with to.be.an('array') for array checks [OK]

Common Mistakes:

• Using pm.response.text() instead of json()
• Checking for 'string' instead of 'array'
• Using pm.response.body without parsing

3. Given this response body: [{"id":1,"name":"Alice"},{"id":2,"name":"Bob"} ], what will this Postman test output?

pm.test('Check length', () => {
  const jsonData = pm.response.json();
  pm.expect(jsonData.length).to.eql(3);
});

medium

A. Test fails because length is 2

B. Test passes because length is undefined

C. Test throws syntax error

D. Test passes because length is 3

Solution

1. Step 1: Parse the response and check array length

   The response JSON is an array with 2 objects, so jsonData.length equals 2.

2. Step 2: Compare expected length with actual length

   The test expects length 3, but actual length is 2, so the assertion fails.

3. Final Answer:

   Test fails because length is 2 -> Option A

4. Quick Check:

   Array length is 2, expected 3, test fails [OK]

Hint: Count array items carefully before asserting length [OK]

Common Mistakes:

• Assuming length is 3 without counting items
• Expecting syntax error when code is correct
• Confusing length property with array content

4. Identify the error in this Postman test code that checks if all items in the response array have an 'id' property:

pm.test('All items have id', () => {
  const jsonData = pm.response.json();
  jsonData.forEach(item => {
    pm.expect(item.id).to.exist;
  });
});

medium

A. pm.expect syntax is incorrect

B. Should use pm.expect(item).to.have.property('id') instead

C. forEach cannot be used on jsonData

D. No error, the test is correct

Solution

1. Step 1: Check if jsonData is an array and forEach usage

   pm.response.json() returns an array, so forEach is valid to iterate over items.

2. Step 2: Validate assertion syntax for property existence

   pm.expect(item.id).to.exist correctly asserts that the 'id' property exists on each item.

3. Final Answer:

   No error, the test is correct -> Option D

4. Quick Check:

   forEach and to.exist used correctly [OK]

Hint: Use forEach with to.exist to check property presence [OK]

Common Mistakes:

• Thinking forEach can't be used on arrays
• Confusing to.exist with to.have.property
• Incorrect pm.expect syntax assumptions

5. You want to assert that the response array contains at least one item with status equal to active. Which Postman test code correctly does this?

hard

A. pm.test('Has active status', () => {
const jsonData = pm.response.json();
pm.expect(jsonData.every(item => item.status === 'active')).to.be.true;
});

B. pm.test('Has active status', () => {
const jsonData = pm.response.json();
pm.expect(jsonData.some(item => item.status === 'active')).to.be.true;
});

C. pm.test('Has active status', () => {
const jsonData = pm.response.json();
pm.expect(jsonData.find(item => item.status === 'active')).to.be.undefined;
});

D. pm.test('Has active status', () => {
const jsonData = pm.response.json();
pm.expect(jsonData.filter(item => item.status === 'active').length).to.eql(0);
});

Solution

1. Step 1: Understand the requirement to find at least one item with status 'active'

   The method some() returns true if any item matches the condition, which fits the requirement.

2. Step 2: Analyze each option's logic

   pm.test('Has active status', () => { const jsonData = pm.response.json(); pm.expect(jsonData.some(item => item.status === 'active')).to.be.true; }); uses some() and expects true, correctly asserting presence. pm.test('Has active status', () => { const jsonData = pm.response.json(); pm.expect(jsonData.every(item => item.status === 'active')).to.be.true; }); uses every(), which requires all items to be active. pm.test('Has active status', () => { const jsonData = pm.response.json(); pm.expect(jsonData.find(item => item.status === 'active')).to.be.undefined; }); expects find() result to be undefined, which means no active items. pm.test('Has active status', () => { const jsonData = pm.response.json(); pm.expect(jsonData.filter(item => item.status === 'active').length).to.eql(0); }); expects filter length to be 0, meaning no active items.

3. Final Answer:

   pm.test('Has active status', () => { const jsonData = pm.response.json(); pm.expect(jsonData.some(item => item.status === 'active')).to.be.true; }); -> Option B

4. Quick Check:

   Use some() to check at least one match [OK]

Hint: Use some() to check if any array item matches condition [OK]

Common Mistakes:

• Using every() which requires all items to match
• Checking for undefined instead of true
• Asserting zero length for presence check