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Last updated: 9 Jul 2021

smart-answers: Deploying changes for fact-check

When making bigger changes that need to be tested or fact-checked before they are deployed to GOV.UK you can make use of [Heroku Review apps][]. These are created automatically when a new PR is opened and will also be automatically linked to from the PR. They will also update on each new commit to the PR.

The main branch of Smart Answers is deployed to Heroku with each update and this allows previewing draft Smart Answers. This is available at

Displaying rates for a specific date

Smart Answers are often used to illustrate certain costs or benefits applicable on a particular date. These are determined by looking up the correct rates (in config/smart_answers/rates) to display for the current date. When testing upcoming changes to rates you may want to simulate how they will appear on a particular date, this can be achieved by setting the RATES_QUERY_DATE environment variable.

To apply this to a particular review app you can set a value for this environment variable in the app.json, for example: "RATES_QUERY_DATE": "2020-04-01" - don't forget to remove this before merging.