test(index): add integration tests for runAction entry point

__tests__/index.spec.ts

@@ -0,0 +1,56 @@
+/*
+ * File: index.spec.ts
+ * Description: Test entry point index.ts
+ * Created: 2026-06-16
+ */
+
+import * as path from 'path'
+import * as core from '@actions/core'
+import { runAction } from '../src/index'
+import { mockAction } from '../src/test-utils'
+
+describe('runAction function', () => {
+  beforeEach(() => {
+    jest.clearAllMocks()
+  })
+
+  test('succeeds when no errors exist', async () => {
+    process.env.GITHUB_WORKSPACE = path.resolve(process.cwd(), 'examples', 'only-warning')
+    mockAction(null as any, '.lintmdrc')
+
+    await runAction()
+
+    expect(core.info).toHaveBeenCalledWith(expect.stringContaining('Markdown Lint free'))
+    expect(core.setFailed).not.toHaveBeenCalled()
+  })
+
+  test('fails when lint errors are detected', async () => {
+    process.env.GITHUB_WORKSPACE = path.resolve(process.cwd(), 'examples', 'use-config-file')
+    mockAction(null as any, '.lintmdrc')
+
+    await runAction()
+
+    expect(core.error).toHaveBeenCalled()
+    expect(core.setFailed).toHaveBeenCalledWith(expect.stringContaining('lint errors'))
+  })
+
+  test('fails when failOnWarnings is true and warnings exist', async () => {
+    process.env.GITHUB_WORKSPACE = path.resolve(process.cwd(), 'examples', 'only-warning')
+    mockAction(null as any, '.lintmdrc', 'true')
+
+    await runAction()
+
+    expect(core.warning).toHaveBeenCalled()
+    expect(core.setFailed).toHaveBeenCalledWith(expect.stringContaining('lint errors'))
+  })
+
+  test('shows lint results and exits gracefully on errors', async () => {
+    process.env.GITHUB_WORKSPACE = path.resolve(process.cwd(), 'examples', 'no-config-file')
+    mockAction()
+
+    await runAction()
+
+    expect(core.error).toHaveBeenCalled()
+    expect(core.setFailed).toHaveBeenCalled()
+  })
+})