Adds FAQ explaining why stories show as new

src/content/troubleshooting/faq/why-tests-show-as-new.md

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+---
+layout: "../../../layouts/FAQLayout.astro"
+sidebar: { hide: true }
+title: Why do tests show as new in builds?
+section: "uiTestsAndReview"
+---
+
+# Why do tests show as new in builds?
+
+Tests are identified by their **story name**, which is a combination of key elements in the test file. If any of these elements change, the test will be considered new. Here's a breakdown of how story names are constructed and why they might change.
+
+## Story Name Construction
+
+The story name is generated from:
+
+1. **File Name**: The name of the test file (e.g., `spec.cy.ts`).
+2. **Describe Block**: The names of `describe` blocks that organize and group related tests.
+3. **It Block**: The name of the specific test within the `it` block.
+
+If **any** of these elements change—file name, `describe` block name, or `it` block name—the story name changes. As a result, Chromatic interprets the test as new because it no longer matches the previously known story name.
+
+### Example
+
+Consider the following test file structure:
+
+- **File name**: `spec.cy.ts`
+- **Describe block**: `template spec`
+- **It block**: `loads homepage`
+
+The story name for this test would be:
+`spec.cy.ts > template spec > loads homepage`
+
+## How to Avoid Unintentional New Stories
+
+To prevent tests from showing as new unintentionally:
+
+- **Keep naming consistent**: Avoid renaming files, `describe` blocks, or `it` blocks unless necessary.
+- **Refactor carefully**: If changes are needed, be aware that the story name will change, and Chromatic will treat it as new.
+- **Review build diffs**: If a test appears as new, check whether the naming structure has been altered.