gnomon-postgres (Ruby)

Helpers for apps on a PostgreSQL database with the gnomon extension: pg and ActiveRecord on a branch, a Rack middleware for a branch per request, RSpec examples on scratch branches, and snapshots of a branch's diff.

require "gnomon"
conn = PG.connect(dbname: "shop", options: Gnomon.branch_options("feature"))  # sessions start on a branch
Gnomon.with_branch(conn, "feature") { conn.exec("update accounts set ...") }   # one transaction
Gnomon.connection_options(conn, "feature")    # what the database says the branch needs

use, create_branch, create_scratch, drop_branch, diff, merge. Rails: require "gnomon/rails", Gnomon::Rails.with_branch(branch) { ... } and the Gnomon::Rails::Middleware (a branch per request from X-Gnomon-Branch); the routing views' primary keys are taught to ActiveRecord.

RSpec:

require "gnomon/rspec"
require "gnomon/testing"
RSpec.configure { |c| Gnomon::RSpec.install(c, -> { ActiveRecord::Base.connection.raw_connection }) }

it "cancels an order" do
  Order.find(1).cancel!
  expect(ActiveRecord::Base.connection.raw_connection).to match_gnomon_snapshot   # GNOMON_UPDATE_SNAPSHOTS=1 records
end

Every example runs on its own scratch branch; tag a group gnomon: false to run it on main. Gnomon::Testing.assert_no_changes and assert_changed check a branch's diff directly. Snapshots use the format and golden files the Python and TypeScript SDKs share.