chore: migrate tests from tests-ui/ to colocate with source files (#7811)

## Summary

Migrates all unit tests from `tests-ui/` to colocate with their source
files in `src/`, improving discoverability and maintainability.

## Changes

- **What**: Relocated all unit tests to be adjacent to the code they
test, following the `<source>.test.ts` naming convention
- **Config**: Updated `vitest.config.ts` to remove `tests-ui` include
pattern and `@tests-ui` alias
- **Docs**: Moved testing documentation to `docs/testing/` with updated
paths and patterns

## Review Focus

- Migration patterns documented in
`temp/plans/migrate-tests-ui-to-src.md`
- Tests use `@/` path aliases instead of relative imports
- Shared fixtures placed in `__fixtures__/` directories

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7811-chore-migrate-tests-from-tests-ui-to-colocate-with-source-files-2da6d73d36508147a4cce85365dee614)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: GitHub Action <action@github.com>

src/schemas/nodeDefSchema.validation.test.ts

@@ -0,0 +1,74 @@
+import { describe, expect, it } from 'vitest'
+
+import { validateComfyNodeDef } from '@/schemas/nodeDefSchema'
+import type { ComfyNodeDef } from '@/schemas/nodeDefSchema'
+
+const EXAMPLE_NODE_DEF: ComfyNodeDef = {
+  input: {
+    required: {
+      ckpt_name: [['model1.safetensors', 'model2.ckpt'], {}]
+    }
+  },
+  output: ['MODEL', 'CLIP', 'VAE'],
+  output_is_list: [false, false, false],
+  output_name: ['MODEL', 'CLIP', 'VAE'],
+  name: 'CheckpointLoaderSimple',
+  display_name: 'Load Checkpoint',
+  description: '',
+  python_module: 'nodes',
+  category: 'loaders',
+  output_node: false,
+  experimental: false,
+  deprecated: false
+}
+
+describe('validateNodeDef', () => {
+  it('Should accept a valid node definition', async () => {
+    expect(validateComfyNodeDef(EXAMPLE_NODE_DEF)).not.toBeNull()
+  })
+
+  describe.each([
+    [{ ckpt_name: ['foo', { default: 1 }] }, ['foo', { default: 1 }]],
+    // Extra input spec should be preserved
+    [{ ckpt_name: ['foo', { bar: 1 }] }, ['foo', { bar: 1 }]],
+    [{ ckpt_name: ['INT', { bar: 1 }] }, ['INT', { bar: 1 }]],
+    [{ ckpt_name: [[1, 2, 3], { bar: 1 }] }, [[1, 2, 3], { bar: 1 }]]
+  ])(
+    'validateComfyNodeDef with various input spec formats',
+    (inputSpec, expected) => {
+      it(`should accept input spec format: ${JSON.stringify(inputSpec)}`, async () => {
+        expect(
+          // @ts-expect-error fixme ts strict error
+          validateComfyNodeDef({
+            ...EXAMPLE_NODE_DEF,
+            input: {
+              required: inputSpec
+            }
+          }).input.required.ckpt_name
+        ).toEqual(expected)
+      })
+    }
+  )
+
+  describe.each([
+    [{ ckpt_name: { 'model1.safetensors': 'foo' } }],
+    [{ ckpt_name: ['*', ''] }],
+    [{ ckpt_name: ['foo', { default: 1 }, { default: 2 }] }],
+    // Should reject incorrect default value type.
+    [{ ckpt_name: ['INT', { default: '124' }] }]
+  ])(
+    'validateComfyNodeDef rejects with various input spec formats',
+    (inputSpec) => {
+      it(`should accept input spec format: ${JSON.stringify(inputSpec)}`, async () => {
+        expect(
+          validateComfyNodeDef({
+            ...EXAMPLE_NODE_DEF,
+            input: {
+              required: inputSpec
+            }
+          })
+        ).toBeNull()
+      })
+    }
+  )
+})