/**
* Unit Tests for Formatter
*
* Tests the formatter functionality including:
* - Error message size limiting
* - Error message truncation
* - No emoji characters in error messages
*
* NOTE: Error responses no longer include structuredContent.
* MCP SDK validates structuredContent against outputSchema if present,
* even when isError: true. Omitting it avoids schema validation failures.
*/
import { describe, expect, it } from 'vitest'
import { MAX_ERROR_LENGTH } from '../../../src/constants.js'
import { formatErrorResponse } from '../../../src/services/formatter.js'
describe('Formatter - Error Message Constraints', () => {
describe('Error Message Size Limiting', () => {
it('should not truncate short error messages', () => {
const shortError = 'This is a short error message.'
const response = formatErrorResponse(shortError)
expect(response.content[0].text).toBe(shortError)
expect(response.isError).toBe(true)
})
it('should truncate error messages exceeding MAX_ERROR_LENGTH', () => {
// Create an error message longer than MAX_ERROR_LENGTH
const longError = 'A'.repeat(MAX_ERROR_LENGTH + 100)
const response = formatErrorResponse(longError)
const expectedTruncated = `${'A'.repeat(MAX_ERROR_LENGTH)}\n\n[Error message truncated - exceeded maximum length]`
expect(response.content[0].text).toBe(expectedTruncated)
expect(response.content[0].text.length).toBeLessThan(longError.length)
})
it('should handle error messages exactly at MAX_ERROR_LENGTH', () => {
const exactLengthError = 'X'.repeat(MAX_ERROR_LENGTH)
const response = formatErrorResponse(exactLengthError)
// Should not be truncated since it's exactly at the limit
expect(response.content[0].text).toBe(exactLengthError)
})
it('should truncate multi-line error messages', () => {
const longMultilineError = 'Line 1\n'.repeat(100) + 'This should be truncated\n'.repeat(100)
const response = formatErrorResponse(longMultilineError)
expect(response.content[0].text.length).toBeLessThanOrEqual(
MAX_ERROR_LENGTH + '\n\n[Error message truncated - exceeded maximum length]'.length
)
expect(response.content[0].text).toContain('[Error message truncated')
})
})
describe('Error Message Content Validation', () => {
it('should not contain emoji characters in error messages', () => {
// Test common emoji that were in old error messages
const errorWithoutEmoji = formatErrorResponse('Error: Invalid data format')
expect(errorWithoutEmoji.content[0].text).not.toContain('❌')
expect(errorWithoutEmoji.content[0].text).not.toContain('✅')
expect(errorWithoutEmoji.content[0].text).not.toContain('💡')
expect(errorWithoutEmoji.content[0].text).not.toContain('📖')
})
it('should append suggestions to text content when provided', () => {
const errorMessage = 'Test error'
const options = {
errorCode: 'TEST_ERROR',
context: { detail: 'Additional context' },
retryable: true,
suggestions: ['Try this', 'Or try that']
}
const response = formatErrorResponse(errorMessage, options)
// Suggestions should be appended to text content
expect(response.content[0].text).toContain('Test error')
expect(response.content[0].text).toContain('**Suggestions:**')
expect(response.content[0].text).toContain('- Try this')
expect(response.content[0].text).toContain('- Or try that')
})
it('should handle error messages with special characters', () => {
const errorWithSpecialChars =
'Error: Invalid character in column "Name" at line 42: unexpected token "&"'
const response = formatErrorResponse(errorWithSpecialChars)
expect(response.content[0].text).toBe(errorWithSpecialChars)
})
})
describe('Error Response Structure', () => {
it('should always have isError flag set to true', () => {
const response = formatErrorResponse('Any error message')
expect(response.isError).toBe(true)
})
it('should always have content array with text type', () => {
const response = formatErrorResponse('Error message')
expect(response.content).toBeInstanceOf(Array)
expect(response.content).toHaveLength(1)
expect(response.content[0].type).toBe('text')
expect(response.content[0].text).toBeTruthy()
})
it('should NOT include structuredContent to avoid output schema validation', () => {
// MCP SDK validates structuredContent against outputSchema if present,
// even when isError: true. We omit structuredContent to avoid this.
const response = formatErrorResponse('Error message')
expect(response.structuredContent).toBeUndefined()
expect(response.isError).toBe(true)
})
})
describe('Truncation Edge Cases', () => {
it('should handle empty error messages', () => {
const response = formatErrorResponse('')
expect(response.content[0].text).toBe('')
})
it('should handle error messages with only whitespace', () => {
const whitespaceError = ' \n\n '
const response = formatErrorResponse(whitespaceError)
expect(response.content[0].text).toBe(whitespaceError)
})
it('should preserve newlines in non-truncated messages', () => {
const multilineError = 'Line 1\nLine 2\nLine 3'
const response = formatErrorResponse(multilineError)
expect(response.content[0].text).toBe(multilineError)
expect(response.content[0].text).toContain('\n')
})
})
})
