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/renderer/extensions/vueNodes/components/NodeWidgets.test.ts

@@ -0,0 +1,123 @@
+import { createTestingPinia } from '@pinia/testing'
+import { mount } from '@vue/test-utils'
+import { describe, expect, it } from 'vitest'
+
+import type {
+  SafeWidgetData,
+  VueNodeData
+} from '@/composables/graph/useGraphNodeManager'
+
+import NodeWidgets from '@/renderer/extensions/vueNodes/components/NodeWidgets.vue'
+
+describe('NodeWidgets', () => {
+  const createMockWidget = (
+    overrides: Partial<SafeWidgetData> = {}
+  ): SafeWidgetData => ({
+    name: 'test_widget',
+    type: 'combo',
+    value: 'test_value',
+    options: {
+      values: ['option1', 'option2']
+    },
+    callback: undefined,
+    spec: undefined,
+    label: undefined,
+    isDOMWidget: false,
+    slotMetadata: undefined,
+    ...overrides
+  })
+
+  const createMockNodeData = (
+    nodeType: string = 'TestNode',
+    widgets: SafeWidgetData[] = []
+  ): VueNodeData => ({
+    id: '1',
+    type: nodeType,
+    widgets,
+    title: 'Test Node',
+    mode: 0,
+    selected: false,
+    executing: false,
+    inputs: [],
+    outputs: []
+  })
+
+  const mountComponent = (nodeData?: VueNodeData) => {
+    return mount(NodeWidgets, {
+      props: {
+        nodeData
+      },
+      global: {
+        plugins: [createTestingPinia()],
+        stubs: {
+          // Stub InputSlot to avoid complex slot registration dependencies
+          InputSlot: true
+        },
+        mocks: {
+          $t: (key: string) => key
+        }
+      }
+    })
+  }
+
+  describe('node-type prop passing', () => {
+    it('passes node type to widget components', () => {
+      const widget = createMockWidget()
+      const nodeData = createMockNodeData('CheckpointLoaderSimple', [widget])
+      const wrapper = mountComponent(nodeData)
+
+      // Find the dynamically rendered widget component
+      const widgetComponent = wrapper.find('.lg-node-widget')
+      expect(widgetComponent.exists()).toBe(true)
+
+      // Verify node-type prop is passed
+      const component = widgetComponent.findComponent({ name: 'WidgetSelect' })
+      if (component.exists()) {
+        expect(component.props('nodeType')).toBe('CheckpointLoaderSimple')
+      }
+    })
+
+    it('passes empty string when nodeData is undefined', () => {
+      const wrapper = mountComponent(undefined)
+
+      // No widgets should be rendered
+      const widgetComponents = wrapper.findAll('.lg-node-widget')
+      expect(widgetComponents).toHaveLength(0)
+    })
+
+    it('passes empty string when nodeData.type is undefined', () => {
+      const widget = createMockWidget()
+      const nodeData = createMockNodeData('', [widget])
+      const wrapper = mountComponent(nodeData)
+
+      const widgetComponent = wrapper.find('.lg-node-widget')
+      if (widgetComponent.exists()) {
+        const component = widgetComponent.findComponent({
+          name: 'WidgetSelect'
+        })
+        if (component.exists()) {
+          expect(component.props('nodeType')).toBe('')
+        }
+      }
+    })
+
+    it.for(['CheckpointLoaderSimple', 'LoraLoader', 'VAELoader', 'KSampler'])(
+      'passes correct node type: %s',
+      (nodeType) => {
+        const widget = createMockWidget()
+        const nodeData = createMockNodeData(nodeType, [widget])
+        const wrapper = mountComponent(nodeData)
+
+        const widgetComponent = wrapper.find('.lg-node-widget')
+        expect(widgetComponent.exists()).toBe(true)
+
+        const component = widgetComponent.findComponent({
+          name: 'WidgetSelect'
+        })
+        if (component.exists()) {
+          expect(component.props('nodeType')).toBe(nodeType)
+        }
+      }
+    )
+  })
+})