test: add tests for aiCore/middleware/utils (#8645)

- Add tests for createErrorChunk function
- Add tests for capitalize function
- Add tests for isAsyncIterable function
- Achieve 100% test coverage

src/renderer/src/aiCore/middleware/__tests__/utils.test.ts

@@ -0,0 +1,79 @@
+import { ChunkType } from '@renderer/types/chunk'
+import { describe, expect, it } from 'vitest'
+
+import { capitalize, createErrorChunk, isAsyncIterable } from '../utils'
+
+describe('utils', () => {
+  describe('createErrorChunk', () => {
+    it('should handle Error instances', () => {
+      const error = new Error('Test error message')
+      const result = createErrorChunk(error)
+
+      expect(result.type).toBe(ChunkType.ERROR)
+      expect(result.error.message).toBe('Test error message')
+      expect(result.error.name).toBe('Error')
+      expect(result.error.stack).toBeDefined()
+    })
+
+    it('should handle string errors', () => {
+      const result = createErrorChunk('Something went wrong')
+      expect(result.error).toEqual({ message: 'Something went wrong' })
+    })
+
+    it('should handle plain objects', () => {
+      const error = { code: 'NETWORK_ERROR', status: 500 }
+      const result = createErrorChunk(error)
+      expect(result.error).toEqual(error)
+    })
+
+    it('should handle null and undefined', () => {
+      expect(createErrorChunk(null).error).toEqual({})
+      expect(createErrorChunk(undefined).error).toEqual({})
+    })
+
+    it('should use custom chunk type when provided', () => {
+      const result = createErrorChunk('error', ChunkType.BLOCK_COMPLETE)
+      expect(result.type).toBe(ChunkType.BLOCK_COMPLETE)
+    })
+
+    it('should use toString for objects without message', () => {
+      const error = {
+        toString: () => 'Custom error'
+      }
+      const result = createErrorChunk(error)
+      expect(result.error.message).toBe('Custom error')
+    })
+  })
+
+  describe('capitalize', () => {
+    it('should capitalize first letter', () => {
+      expect(capitalize('hello')).toBe('Hello')
+      expect(capitalize('a')).toBe('A')
+    })
+
+    it('should handle edge cases', () => {
+      expect(capitalize('')).toBe('')
+      expect(capitalize('123')).toBe('123')
+      expect(capitalize('Hello')).toBe('Hello')
+    })
+  })
+
+  describe('isAsyncIterable', () => {
+    it('should identify async iterables', () => {
+      async function* gen() {
+        yield 1
+      }
+      expect(isAsyncIterable(gen())).toBe(true)
+      expect(isAsyncIterable({ [Symbol.asyncIterator]: () => {} })).toBe(true)
+    })
+
+    it('should reject non-async iterables', () => {
+      expect(isAsyncIterable([1, 2, 3])).toBe(false)
+      expect(isAsyncIterable(new Set())).toBe(false)
+      expect(isAsyncIterable({})).toBe(false)
+      expect(isAsyncIterable(null)).toBe(false)
+      expect(isAsyncIterable(123)).toBe(false)
+      expect(isAsyncIterable('string')).toBe(false)
+    })
+  })
+})