Collection composition

[ShahOdin]

I have done some spikes into composing collections so that a business use-case can be created by composing individual collections. In the process, I have examined the different components that can overlap and thought you guys might appreciate the insight.

Before I go ahead and create my own little library, is this something postman team will be interested in pursuing?

[shamasis]

That’s a great. At Postman we support and appreciate our community leveraging the collection concept itself to amplify the value they derive out of Postman platform.

I would love to see what you develop and would be more than glad to be part of the process in any way feasible. At the moment, composing collections to form a scenario is in our feature list but not in near term horizon.

[ShahOdin]

Sure. So...

Requirements

1. Works on top of collections and doesn't require the collection themselves to have any notion of this sequencing. ie, nothing like postman.setNextRequest()

2. Should ideally work for both postman and newman.

3. Allows the full usage of all scopes. ie, collectionVariables, etc.

Case study

We examine the following requests and apply different solutions to them. We have three collections of the form:

• Foo.postman_collection.json : Config => Foo

• Bar.postman_collection.json : Config => Bar

• FooBar.postman_collection.json : (Foo, Bar) => FooBar

[ShahOdin]

Solution A

description

This is currently my only working solution. It's a newman only solution that works with the environment scope only. It makes use of export-environment flag in newman's run command.

We can run:

  cp envs.postman_environment.json envs-mutable.postman_environment.json

  newman run Foo.postman_collection.json \
  -e envs-mutable.postman_environment.json \
  --export-environment envs-mutable.postman_environment.json &&

  newman run Bar.postman_collection.json \
  -e envs-mutable.postman_environment.json \
  --export-environment envs-mutable.postman_environment.json &&

  newman run FooBar.postman_collection.json \
  -e envs-mutable.postman_environment.json \
  --export-environment envs-mutable.postman_environment.json
  /

The envs-mutable.postman_environment does the job of passing the context around. In this case, the context is only the environment scope variables.

Pros & Cons

• It satisfies requirement 1 beautifully.
• It doesn't respect requirement 2. The composition happens at newman level and is tied to the execution.
• Lastly, doesn't respect requirement 3: The solution is limited to the environment scope only since newman doesn't allow exporting the full context/"session".

Summary

This is a good solution for CI purposes that uses Newman.

[ShahOdin]

Solution B

description

Taking the idea behind req.1 a step further, we could say this composition process should happen independently of Postman/Newman and that this process should generate a combined collection. If we can achieve such a combined collection, then the requests can have full access to the collectionVarriables scope too for instance since it's just one big collection. Also, if this is just a single collection, Newman/Postman should just handle it as normal.

I looked around and came across postman-combine-collections. This looked like exactly what I wanted. Sadly it doesn't respect order and it only generates a collection with the specified collections present. If it did, I could have something of the form:

  postman-combine-collections --name composed \
  -f Foo.postman_collection.json \
  -f Bar.postman_collection.json \
  -f FooBar.postman_collection.json \
  -o composed.collection.json \
  /

to generate a single collection which can then be run in Postman/Newman.

Ideally, it should also accept a json with a postman-defined schema, containing an ordered list of the address of the collections to be composed. That would be really handy for CI purposes.

Pros & Cons

• It satisfies requirement 1.
• It satisfies requirement 2. The composition happens independently of execution.
• It satisfies requirement 3.

Summary

The only problem is, there currently isn't a library that supports this ordered combination feature. Ideally, this could be something that can be developed externally to newman/postman. In future, it could perhaps be added to them as a special type of import to Postman and as a command in Newman separate from run.

[ShahOdin]

I would love to see what you develop and would be more than glad to be part of the process in any way feasible.

Hi @shamasis did you get the chance to have a look at this? would love to have your feedback.