test: add Playwright tests for clearHistory()

Tests verify:
- Undo cannot revert into a pre-refresh diagram after clearHistory()
- Operations performed after clearHistory() are themselves undoable/redoable
- The first undo baseline is the refreshed diagram state, not a prior one

Author: DisciplinedSoftware

tests/clear-history.spec.ts

@@ -0,0 +1,107 @@
+import { test, expect } from './mind-elixir-test'
+
+const diagramA = {
+  nodeData: {
+    id: 'root-a',
+    topic: 'Diagram A',
+    children: [
+      { id: 'child-a', topic: 'Child A' },
+    ],
+  },
+}
+
+const diagramB = {
+  nodeData: {
+    id: 'root-b',
+    topic: 'Diagram B',
+    children: [
+      { id: 'child-b', topic: 'Child B' },
+    ],
+  },
+}
+
+test.beforeEach(async ({ me }) => {
+  await me.init(diagramA)
+})
+
+test('clearHistory - undo cannot revert into the pre-refresh diagram', async ({ page, me }) => {
+  // Perform an operation in Diagram A
+  await me.click('Child A')
+  await page.keyboard.press('Tab')
+  await page.keyboard.press('Enter')
+  await expect(me.getByText('New Node')).toBeVisible()
+
+  // Load a new diagram and clear the history
+  await page.evaluate(data => {
+    const mind = (window as any)['#map']
+    mind.refresh(data)
+    mind.clearHistory()
+  }, diagramB)
+
+  // Diagram B should now be shown
+  await expect(me.getByText('Diagram B')).toBeVisible()
+  await expect(me.getByText('Diagram A')).toBeHidden()
+
+  // Undo should NOT travel back into Diagram A
+  await page.keyboard.press('Control+z')
+  await expect(me.getByText('Diagram B')).toBeVisible()
+  await expect(me.getByText('Diagram A')).toBeHidden()
+
+  // Redo should also be a no-op
+  await page.keyboard.press('Control+y')
+  await expect(me.getByText('Diagram B')).toBeVisible()
+  await expect(me.getByText('Diagram A')).toBeHidden()
+})
+
+test('clearHistory - operations after clearHistory are undoable normally', async ({ page, me }) => {
+  // Perform an operation in Diagram A then load Diagram B and clear history
+  await me.click('Child A')
+  await page.keyboard.press('Delete')
+  await expect(me.getByText('Child A')).toBeHidden()
+
+  await page.evaluate(data => {
+    const mind = (window as any)['#map']
+    mind.refresh(data)
+    mind.clearHistory()
+  }, diagramB)
+
+  // Now add a node to Diagram B
+  await me.click('Child B')
+  await page.keyboard.press('Tab')
+  await page.keyboard.press('Enter')
+  await expect(me.getByText('New Node')).toBeVisible()
+
+  // Undo the add — should work
+  await page.keyboard.press('Control+z')
+  await expect(me.getByText('New Node')).toBeHidden()
+
+  // Redo the add — should also work
+  await page.keyboard.press('Control+y')
+  await expect(me.getByText('New Node')).toBeVisible()
+
+  // One more undo should be a no-op (no history before the cleared point)
+  await page.keyboard.press('Control+z') // undo add
+  await page.keyboard.press('Control+z') // should be no-op, not reach Diagram A
+  await expect(me.getByText('Diagram B')).toBeVisible()
+  await expect(me.getByText('Diagram A')).toBeHidden()
+})
+
+test('clearHistory - first undo baseline is the refreshed diagram state', async ({ page, me }) => {
+  // Load Diagram B, clear history, then add a node and undo
+  await page.evaluate(data => {
+    const mind = (window as any)['#map']
+    mind.refresh(data)
+    mind.clearHistory()
+  }, diagramB)
+
+  await me.click('Child B')
+  await page.keyboard.press('Tab')
+  await page.keyboard.press('Enter')
+  await expect(me.getByText('New Node')).toBeVisible()
+
+  // Undo restores exactly to the state right after refresh (Diagram B with just Child B)
+  await page.keyboard.press('Control+z')
+  await expect(me.getByText('New Node')).toBeHidden()
+  await expect(me.getByText('Child B')).toBeVisible()
+  await expect(me.getByText('Diagram B')).toBeVisible()
+})