# Pre-population, validation and testing

Source: https://govform.com/resources/documentation/article/03-pre-population-validation-and-testing
Topic: Tutorials

Continue from [Uploads and conditional page flow](<https://govform.com/resources/documentation/article/02-uploads-and-conditional-page-flow>). You will pre-fill an answer from an earlier page, add a validation condition, inspect journey data and review versions before a QA release.

The calculation uses a fixed 20% rate as a learning example, based on the claim amount _excluding VAT_. Replace the sample rule with your service’s actual requirements before using it for real claims.

## 1\. Work from a copy

1.  Return to your library’s **Services** list. Tick the checkbox for your Tutorial 2 service, then select **Duplicate**.
2.  Keep the same **Destination library**, enter a new **Service ID** such as `tutorial-3-pre-fill-and-testing`, and select **Duplicate service**.
3.  Open the copy. In **Service settings → Service details**, set its name to “Tutorial 3 — pre-fill and testing” and select **Apply**.

![Duplicate service dialog with Demo library selected and a new tutorial service ID entered.](<https://govform.com/images/documentation/tutorials/03-duplicate-service.jpg>)

Duplicate the service with a new service ID; keep its existing component IDs, including `claimAmount` and `vatAmount`.

## 2\. Put VAT on the following page

For this example, the claim amount must be saved before the VAT page opens. Moving the existing component preserves its ID and validation settings.

1.  Open “About your claim” and select **Add next page → Empty page**. Title it “VAT amount for your claim”, then select **Add page**.
2.  Return to “About your claim”. Open the **Component menu** beside the VAT amount component and select **Cut component**.
3.  Open the new VAT page and select **Paste component from page 4** (the page number reflects its source). “About your claim” should now contain only `claimAmount`, with `vatAmount` on the next page.

## 3\. Pre-fill VAT

1.  Select the VAT amount component and open **Pre-fill**.
2.  Enter this **Pre-population template**:

```
{% if claimAmount != blank and claimAmount != 0 %}{{ claimAmount | times: 0.2 | round_fixed: 2 }}{% endif %}
```

Leave **Allow changes** enabled so you can test validation next. Click outside the editor and wait for **Saved**. This example uses a previous page’s saved answer, so leave in-page recalculation off.

![VAT component Pre-fill settings showing the Liquid template and Allow changes enabled.](<https://govform.com/images/documentation/tutorials/03-pre-fill.jpg>)

**Pre-fill** supplies the initial answer; it does not validate an answer someone edits.

Open **User view** and follow the valid-receipt route. Enter `100` for the claim amount and select **Continue**. The next page should show `20.00`. Starting a fresh test with `19.99` should give `4.00`.

![User view showing VAT amount for your claim with a £20 answer.](<https://govform.com/images/documentation/tutorials/03-prefilled-vat.jpg>)

The VAT page reads the amount saved on the preceding page.

The template returns nothing for a blank or numeric zero input. The claim amount’s required and minimum-value rules reject those inputs before this page. A user’s explicit override is an answer in its own right; check it when they change an earlier amount rather than assuming pre-fill always replaces it.

## 4\. Validate the edited answer

1.  Open **Service settings → Conditions → Add condition**. Name it “VAT matches the tutorial calculation”, use `vatMatchesCalculation` as its ID, choose **Template**, and select **Continue**.
2.  In **Condition template**, enter the following and select **Apply**:

```
{% assign expectedVat = claimAmount | times: 0.2 | round_fixed: 2 %}
{% assign enteredVat = vatAmount | plus: 0 | round_fixed: 2 %}
{% if enteredVat == expectedVat %}true{% else %}false{% endif %}
```

3.  Return to the VAT page, select its component, then open **Validation conditions**. Choose **Use saved conditions** and add “VAT matches the tutorial calculation”.
4.  Set **Error message** to “Enter 20% of the claim amount excluding VAT for this tutorial.” Wait for **Saved** in the side pane, or select **Apply changes** if you opened the full settings screen.
5.  In User view, try changing VAT from `20.00` to `19` and continuing. Check the custom error, then enter `20` and confirm you can continue.

![VAT Validation conditions with Use saved conditions selected, the calculation condition attached and a custom error message.](<https://govform.com/images/documentation/tutorials/03-validation-conditions.jpg>)

Attach the condition to the VAT component’s **Validation conditions**, keeping its normal required and number rules.

The template compares both amounts rounded to two decimal places, so `20` and `20.00` are treated alike. This condition validates the field; it does not decide whether the VAT page is shown.

## 5\. Use the data inspector

1.  Enter and continue past the claim and VAT pages in User view so the journey has saved values.
2.  Open **User view tools → Data inspector**. In **Form data explorer**, find `claimAmount` and `vatAmount`. Check their IDs and values.
3.  Paste the pre-fill template into **Liquid template tester → Template**, choose **Evaluate as → Value**, and select **Evaluate template**. With a claim amount of `100`, the result should be `20.00`.

![Prototype data inspector showing claim amount 100, VAT amount 20, the Liquid tester and result 20.00.](<https://govform.com/images/documentation/tutorials/03-data-inspector.jpg>)

The tester evaluates against this journey’s saved data. Use **Return to prototype** to try different answers and evaluate again.

You can also use **Preview Liquid output** beneath a component’s template to open the tester with that expression. It may open a different prototype journey; check its captured values first. Testing an expression does not save it back to the component.

## 6\. Review version history

Open **Change management**. The **Publishing status** cards compare the current draft with deployed environments. The **Change history** table records saved changes, including automatically saved component edits.

![Change management showing current draft, environment publishing status and the change history table.](<https://govform.com/images/documentation/tutorials/03-change-management.jpg>)

**Change management** shows saved versions and whether an environment has been deployed.

Select two version checkboxes and choose **Compare selected versions** to inspect their differences. **Undo latest change** and **Restore selected version** change the Builder draft; they do not deploy that design. Review the selected version and the confirmation before restoring. You do not need to restore anything to complete this tutorial.

## 7\. Test and review a QA release

First complete the User view journey through upload, check answers and confirmation. Repeat the two receipt exit routes, missing and invalid values, rounding, Back links and changes from Check your answers. Use **User view tools → Reset prototype → Clear data and restart** for independent test cases.

1.  When you have permission to publish a test version, open **Environments → QA environment**.
2.  Select **Deploy to QA**. In the **Deploy to QA?** dialog, review **Select version to deploy to QA** and the service name. Choose the tested version offered by the picker.
3.  Select **Deploy service** only when you intend to publish that version to QA. To practise reviewing the release without deploying it, select **Cancel**.
4.  After an intended deployment finishes, use the QA service link shown by Builder and repeat the relevant tests there.

![Deploy to QA review dialog with the current version selected and Deploy service and Cancel buttons.](<https://govform.com/images/documentation/tutorials/03-qa-deployment-review.jpg>)

The QA review dialog confirms the service and version before deployment.

QA requires Govform sign-in and access to the library, including the External QA tester role where appropriate. User view simulates integrations; real email, API and other integration tests belong in QA with suitable test destinations. The tutorial service has no real expense-processing integration.

## What you learned

-   Duplicate a service and move a component without changing its ID.
-   Pre-fill from a saved answer and validate an edited value.
-   Test Liquid against journey data.
-   Compare saved versions and review a deliberate QA deployment.