Postman Flows: A Block Reference Guide

In my earlier blog post, I talked about Postman’s latest beta feature, Flows. This feature allows you to chain requests in a low/no code format. To build your own Flow, instead of using complex JavaScript in pre-request/test tabs, you move widgets called “Blocks” around on a canvas to allow you to easily visualise what is happening to the information as it Flows. For example, if I create a user, I can take the ID from the response body of my API call and pass it into my next request, loop or variable. Think of it a like using lego or duplo blocks to build a bridge from one place to another – your bridge is a lot more stable if you link the blocks together than if you simply place them side by side.

TLDR: You can find a great living GitHub page from the Postman team that describes a lot of what I am saying below here.

How can I access the blocks I need to create my Flow?

There are currently a few ways to view and add blocks to your Flow.

  • After creating a new flow, hit the “Add Block” plus sign next to the orange Start Button at the bottom of the canvas. This allows you to scroll through the blocks. When you select a block, it will create a standalone widget, that you can move to wherever you like in the Flow. Useful for when playing around or laying out larger flows.
Add block icon used to generate a Block list
  • After creating a new flow, a block list containing all the blocks you can select is auto-generated and connected via a “noodle” link to the start button. This allows you to get started on your flow straight away.
Example of clicking Event to the right of start button to generate Block list
  • Pressing the blue plus (“+”) icon to the right of an existing block will bring up the block list and allow you to continue your flow based on the outcome of the previous block.

Here is a quick vid to demonstrate all of these methods. Super quick and easy right?

But what do each of the blocks actually do?

Here is my brief reference guide. I’ll try to update this as and when Postman releases updates – which they do regularly. In fact, their latest block, named Check, was only released just this week. Exciting times!

Once you’ve found the block you need, either scroll through the blocklist or click into the Search field and begin to type the block name. Clicking on the name will create that block, that you can customise with input and/or output data to build your flow.

Block NameDescriptionExampleInputsOutputs
Send RequestPerforms a GET/POST/DELETE etc. Send a GET Booking request from API collection Restful Booker using Environment “Production”VariablesResponse
ConditionMake a condition check and fork the data to either accept or reject.If the status code is 200 AcceptDataAccept Reject
CheckPass the data through if the check passes. Can take inputs from 2 sources.If the BookingID does not exist AND the ping generates 200 then pass the data to the next block. Primary SecondaryPrimary
TerminalShows output logs. Note actual log data generated shown in terminal block top right hand corner of canvas.End of the line. Show all logs of all request that have made it through the flow.Data
Assign VariablesAssign data to variables and pass it to a requestTake the “token” value from the response body and assign this to an existing variable named “token”. DataVariables
Create VariablesGenerate a new variable(s)Take the userId from response of POST user endpoint and create a new variable called “newUserId”TriggerVariables
Parse JSONConvert text input data to JSON treeThe equivalent of var jsonData = pm.response.json();
Allowing interrogation of response body data.
DelayWait for specified duration before passing data throughWait for 300[milliseconds] before checking status code in order to allow for integration points e.g. database query, third party API.DataData
Test SummaryAggregates all assertions to generate a report. Note actual test summary data generated shown in test summary block top right hand corner of canvas.Tests Passed: 20Test
For EachPerforms a for each loop to iterate through each item in a listFor each ID in the response body, do X.DataItem
ConcatenateConcatenate two data packets together into a listTake all the users from endpoint A and add them to a list of all the rooms from endpoint B to make List C.List (data from first source)
Data (data from second source)
MergeMerge the source Object to the target ObjectTake all the users from endpoint A and merge them with all the users from endpoint B and output all the unique users into list C.Target
List – PopExtract the first element from the listGet the users from list C and “pop” the first user. Do this with the first user and do that with the rest.DataFirst
Group ByGrouping elements in a listTake list C and output all the users who have an ID from 1-100 into a group called “first_100_users”DataGroup
Table showing each Postman Flow Block, alongside a description, example and input and outputs.

I hope this has helped to get those juices whirring and thinking up all the ways you can use the list items to create some simple, or more advanced Flows. I am far from a Postman expert, so am always happy to hear feedback on changes to the content – if it doesn’t make sense then I want to hear about it!

See you soon, thanks for reading.


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