Graphgen
Generate a graph of values declaratively based on probability distributions
For test cases, local development, and application previews, we already appreciate the incredible value of having high-fidelity fake data. The problem is how do we obtain it? And how do we keep it fresh?
The simplest way to accomplish this is with “fixtures”: static snapshots that can be saved on disk and loaded into the system on demand. However, maintaining such fixtures is a tedious process because the data must conform to your schema, and as the schema evolves, so to must your fixtures.
Factories partially alleviate this problem by parameterizing and
automating the generation of parts of your scghema data. That way, as your
schema evolves, rather than having to update entire data sets, you
only have to update your factories. However, this also falls short for
two reasons. First, is that you still have to write and maintain
factories which for large schemas can be cumbersome. The second is
that factories as we know them are really bad at generating networks
of data, and so we see hacks and workarounds like afterCreate()
hooks to generate related data after a portion of data has been
created. The problem with these is that they
are not declarative (it is very difficult to parameterize afterCreate
hooks), and they are not whole-meal. In other words, they only
consider what happens next after creating a singe datum and not the
entire set as a whole.
Our goal here is to make high fidelity data that
- is always valid no matter which context it is being generated from
- requires a minimum of maintenance. Having a representation of your schema, whether in SDL, OpenAPI, or even just TypeScript, should be sufficient to create a highly realistic data set.
We take a probablistic approach to generating the data where we assume that our data adheres to some statistical distribution of values. We can then sample from that distribution to simulate a realistic value.
Development
While it works in both browser and Node, Deno is the primary development tool. You will need to install that first.
checkout:
$ git clone git@github.com:thefrontside/graphgen.gittest:
$ deno test