Assertions

Assertions let you define expected conditions on a response and evaluate them automatically after each request. The result appears inline in the request panel and in the response panel as a pass/fail list. No scripting required.

Accessing Assertions

Open a request and click the Tests tab. The tab shows a count badge when assertions are defined, for example “Tests (3)”.

Click Add Test to create a new assertion row.

Assertion Structure

Each assertion has four fields:

Field	Description
Checkbox	Enable or disable the assertion without deleting it
Target	What to test (status, body, JSONPath, header, etc.)
Property	Context-dependent input, such as a JSONPath expression or header name
Operator	How to compare the actual value to the expected value
Expected	The value to compare against

Targets

Target	Property field	Description
Status Code	(none)	The HTTP response status code
Response Time	(none)	Request duration in milliseconds
Response Size	(none)	Response body size in bytes
Response Body	(none)	Full response body as a string
JSON Path	JSONPath expression (e.g., $.data[0].name)	A value extracted from the JSON response body
Header	Header name (case-insensitive)	A response header value
Content-Type	(none)	Value of the Content-Type header
JSON Schema	(none)	Validates the response body against a JSON Schema you provide in the Expected field.
Set Variable	JSONPath expression	Extracts a value and stores it as an environment variable.

gRPC Targets

The following targets are available when the request protocol is gRPC:

Target	Property field	Description
gRPC Status Name	(none)	The gRPC status code name (e.g., OK, NOT_FOUND, UNAVAILABLE)
gRPC Trailer	Trailer key	A value from the gRPC response trailers
Stream Msg Count	(none)	Total number of messages received in a streaming call
Stream Message	Index or index + JSONPath	A specific stream message by index, or a field within it. Use 0 for the first message, or 0.$.field to extract a field with JSONPath.

Operators

Operator	Symbol	Notes
equals	=	Numeric-aware comparison
not equals	!=
contains	contains	Substring match
not contains	!contains
starts with	startsWith
ends with	endsWith
greater than	>	Numeric
less than	<	Numeric
greater than or equal	>=	Numeric
less than or equal	<=	Numeric
exists	exists	Value is not null or undefined (no Expected input)
not exists	!exists	Value is null or undefined (no Expected input)
is type	isType	JSON type check: string, number, boolean, array, object, null
is JSON	isJSON	The value is parseable JSON (no Expected input)
count	count	Array length or object key count
matches	regex	JavaScript regular expression
any item equals	anyItemEquals	At least one array item equals the expected value
any item contains	anyItemContains	At least one array item contains the expected string
any item starts with	anyItemStartsWith	At least one array item starts with the expected string
any item ends with	anyItemEndsWith	At least one array item ends with the expected string

Set Variable

Set Variable is a special target that extracts a value from the response and stores it in an environment variable. It does not produce a pass/fail result.

• Property: JSONPath expression pointing to the value to extract (e.g., $.data.token)
• Variable Name: the environment variable name to set (e.g., authToken)

After the request runs, the extracted value is available as {{authToken}} in subsequent requests. In the Collection Runner, Set Variable assertions run in order, so you can chain requests: extract a login token in one request and use it in the next.

Results

In the Request Panel

After sending a request, each assertion row shows a green checkmark or red cross. Failed assertions expand to show the actual value received. The Tests tab header shows a summary like “3/5 passed”.

In the Response Panel

A Tests tab appears in the response section alongside Body, Headers, and Cookies. It shows:

• A summary bar: “X/Y tests passed”
• A per-assertion list with pass/fail icons and the actual value for failures

In the Collection Runner

The runner results table shows an assertion badge per request (e.g., “3/4”). Click a row to expand and see individual assertion details for that request.

Examples

Validate status and speed

Status Code  =        200
Response Time <       500

Check a JSON field exists and has the right type

JSON Path  $.data        exists
JSON Path  $.data.users  isType   array
JSON Path  $.data.total  >        0

Extract a token for use in subsequent requests

Set Variable  $.token  (variable name: authToken)

In the next request, set the Authorization header to Bearer {{authToken}}.

Validate a gRPC streaming call

gRPC Status Name   =       OK
Stream Msg Count   >=      3
Stream Message     0.$.id  exists

Persistence

Assertions are saved as part of the request in your collection. They are included in Postman export and restored on Postman import.