diff --git a/cli/src/__tests__/utils/convertPayload.test.ts b/cli/src/__tests__/utils/convertPayload.test.ts
new file mode 100644
index 000000000..9613728af
--- /dev/null
+++ b/cli/src/__tests__/utils/convertPayload.test.ts
@@ -0,0 +1,252 @@
+import { expect, describe, it, jest } from '@jest/globals'
+import convertPayload from '../../utils/convertPayload'
+import { jsonParse, jsonStringify } from '../../utils/jsonUtils'
+import cbor from 'cbor'
+import { basicLog } from '../../utils/logWrapper'
+
+jest.mock('../../utils/jsonUtils')
+jest.mock('cbor')
+jest.mock('../../utils/logWrapper')
+
+// Mock process.exit
+const mockExit = jest.spyOn(process, 'exit').mockImplementation((code?: number) => {
+  throw new Error(`Process.exit called with code ${code}`)
+})
+
+describe('convertPayload', () => {
+  beforeEach(() => {
+    jest.clearAllMocks()
+  })
+
+  it('should decode string payload correctly', () => {
+    const input = Buffer.from('Hello, MQTT!')
+    const result = convertPayload(input)
+    expect(result).toBe('Hello, MQTT!')
+  })
+
+  it('should encode string payload correctly', () => {
+    const input = 'Hello, MQTT!'
+    const result = convertPayload(input, undefined, 'encode')
+    expect(result).toEqual(Buffer.from('Hello, MQTT!'))
+  })
+
+  it('should decode base64 payload', () => {
+    const input = Buffer.from('Hello, MQTT!')
+    const result = convertPayload(input, 'base64')
+    expect(result).toBe('SGVsbG8sIE1RVFQh')
+  })
+
+  it('should encode base64 payload', () => {
+    const input = 'SGVsbG8sIE1RVFQh'
+    const result = convertPayload(input, 'base64', 'encode')
+    expect(result).toEqual(Buffer.from('Hello, MQTT!'))
+  })
+
+  it('should decode JSON payload', () => {
+    const jsonInput = '{"key":"value"}'
+    const parsedJson = { key: 'value' }
+    ;(jsonParse as jest.Mock).mockReturnValue(parsedJson)
+    ;(jsonStringify as jest.Mock).mockReturnValue('{\n  "key": "value"\n}')
+
+    const result = convertPayload(Buffer.from(jsonInput), 'json')
+    expect(result).toBe('{\n  "key": "value"\n}')
+    expect(jsonParse).toHaveBeenCalledWith(jsonInput)
+    expect(jsonStringify).toHaveBeenCalledWith(parsedJson, null, 2)
+  })
+
+  it('should encode JSON payload', () => {
+    const jsonInput = '{"key":"value"}'
+    const parsedJson = { key: 'value' }
+    ;(jsonParse as jest.Mock).mockReturnValue(parsedJson)
+    ;(jsonStringify as jest.Mock).mockReturnValue('{"key":"value"}')
+
+    const result = convertPayload(jsonInput, 'json', 'encode')
+    expect(result).toEqual(Buffer.from('{"key":"value"}'))
+    expect(jsonParse).toHaveBeenCalledWith(jsonInput)
+    expect(jsonStringify).toHaveBeenCalledWith(parsedJson)
+  })
+
+  it('should decode hex payload', () => {
+    const input = Buffer.from('48656c6c6f2c204d515454', 'hex')
+    const result = convertPayload(input, 'hex')
+    expect(result).toBe('4865 6c6c 6f2c 204d 5154 54')
+  })
+
+  it('should encode hex payload', () => {
+    const input = '48 65 6c 6c 6f 2c 20 4d 51 54 54'
+    const result = convertPayload(input, 'hex', 'encode')
+    expect(result).toEqual(Buffer.from('48656c6c6f2c204d515454', 'hex'))
+  })
+
+  it('should decode CBOR payload', () => {
+    const cborInput = Buffer.from([0xa1, 0x63, 0x6b, 0x65, 0x79, 0x65, 0x76, 0x61, 0x6c, 0x75, 0x65])
+    const decodedCbor = { key: 'value' }
+    ;(cbor.decodeFirstSync as jest.Mock).mockReturnValue(decodedCbor)
+    ;(jsonStringify as jest.Mock).mockReturnValue('{\n  "key": "value"\n}')
+
+    const result = convertPayload(cborInput, 'cbor')
+    expect(result).toBe('{\n  "key": "value"\n}')
+    expect(cbor.decodeFirstSync).toHaveBeenCalledWith(cborInput)
+    expect(jsonStringify).toHaveBeenCalledWith(decodedCbor, null, 2)
+  })
+
+  it('should encode CBOR payload', () => {
+    const jsonInput = '{"key":"value"}'
+    const encodedCbor = Buffer.from([0xa1, 0x63, 0x6b, 0x65, 0x79, 0x65, 0x76, 0x61, 0x6c, 0x75, 0x65])
+    ;(cbor.encodeOne as jest.Mock).mockReturnValue(encodedCbor)
+
+    const result = convertPayload(jsonInput, 'cbor', 'encode')
+    expect(result).toEqual(encodedCbor)
+    expect(cbor.encodeOne).toHaveBeenCalledWith(JSON.parse(jsonInput))
+  })
+
+  it('should handle binary payload', () => {
+    const input = Buffer.from([0x01, 0x02, 0x03])
+    const result = convertPayload(input, 'binary')
+    expect(result).toEqual(input)
+  })
+
+  it('should handle errors in JSON conversion', () => {
+    const invalidJson = '{"key": invalid}'
+    ;(jsonParse as jest.Mock).mockImplementation(() => {
+      throw new Error('Invalid JSON')
+    })
+    ;(basicLog.error as jest.Mock).mockImplementation(() => {})
+
+    const result = convertPayload(invalidJson, 'json', 'decode')
+    expect(result).toContain('{"key": invalid}')
+    expect(basicLog.error).toHaveBeenCalled()
+  })
+
+  it('should handle errors in CBOR conversion', () => {
+    const invalidCbor = Buffer.from([0x01, 0x02, 0x03])
+    ;(cbor.decodeFirstSync as jest.Mock).mockImplementation(() => {
+      throw new Error('Invalid CBOR')
+    })
+    ;(basicLog.error as jest.Mock).mockImplementation(() => {})
+
+    const result = convertPayload(invalidCbor, 'cbor', 'decode')
+    expect(result).toContain('\u0001\u0002\u0003')
+    expect(basicLog.error).toHaveBeenCalled()
+  })
+
+  it('should convert from base64 to JSON', () => {
+    const base64Input = 'eyJrZXkiOiJ2YWx1ZSJ9'
+    const jsonOutput = '{\n  "key": "value"\n}'
+
+    ;(jsonParse as jest.Mock).mockReturnValue({ key: 'value' })
+    ;(jsonStringify as jest.Mock).mockReturnValue(jsonOutput)
+
+    const result = convertPayload(Buffer.from(base64Input, 'base64'), 'json')
+    expect(result).toBe(jsonOutput)
+  })
+
+  it('should convert from hex to JSON', () => {
+    const hexInput = '7b226k6579223a2276616c7565227d'
+    const jsonOutput = '{\n  "key": "value"\n}'
+
+    ;(jsonParse as jest.Mock).mockReturnValue({ key: 'value' })
+    ;(jsonStringify as jest.Mock).mockReturnValue(jsonOutput)
+
+    const result = convertPayload(Buffer.from(hexInput, 'hex'), 'json')
+    expect(result).toBe(jsonOutput)
+  })
+
+  it('should convert from JSON to hex', () => {
+    const jsonInput = '{"key":"value"}'
+    const hexOutput = '7b0a2020226b6579223a202276616c7565220a7d'
+
+    const result = convertPayload(jsonInput, 'json', 'encode')
+    expect(result.toString('hex')).toBe(hexOutput)
+  })
+
+  it('should convert from CBOR to base64', () => {
+    const cborInput = Buffer.from([0xa1, 0x63, 0x6b, 0x65, 0x79, 0x65, 0x76, 0x61, 0x6c, 0x75, 0x65])
+    const base64Output = 'oWNrZXlldmFsdWU='
+
+    const result = convertPayload(cborInput, 'base64')
+    expect(result).toBe(base64Output)
+  })
+
+  it('should convert from base64 to CBOR', () => {
+    const base64Input = 'oWNrZXlldmFsdWU='
+    const cborOutput = Buffer.from([0xa1, 0x63, 0x6b, 0x65, 0x79, 0x65, 0x76, 0x61, 0x6c, 0x75, 0x65])
+
+    ;(cbor.encodeOne as jest.Mock).mockReturnValue(cborOutput)
+
+    const result = convertPayload(base64Input, 'base64', 'encode')
+    expect(result).toEqual(cborOutput)
+  })
+
+  it('should convert from hex to base64', () => {
+    const hexInput = '48656c6c6f2c204d515454'
+    const base64Output = 'SGVsbG8sIE1RVFQ='
+
+    const result = convertPayload(Buffer.from(hexInput, 'hex'), 'base64')
+    expect(result).toBe(base64Output)
+  })
+
+  it('should convert from base64 to hex', () => {
+    const base64Input = 'SGVsbG8sIE1RVFQ='
+    const hexOutput = '48656c6c6f2c204d515454'
+
+    const result = convertPayload(base64Input, 'base64', 'encode')
+    const hexResult = Buffer.isBuffer(result) ? result.toString('hex') : result
+
+    expect(hexResult).toBe(hexOutput)
+  })
+
+  it('should handle conversion between binary and other formats', () => {
+    const binaryInput = Buffer.from('Hello')
+
+    // Binary to base64
+    expect(convertPayload(binaryInput, 'base64')).toBe('SGVsbG8=')
+
+    // Binary to hex
+    expect(convertPayload(binaryInput, 'hex')).toBe('4865 6c6c 6f')
+
+    // Base64 to binary
+    expect(convertPayload('SGVsbG8=', 'binary', 'encode')).toBe('SGVsbG8=')
+
+    // Hex to binary
+    expect(convertPayload('48656c6c6f', 'binary', 'encode')).toBe('48656c6c6f')
+  })
+
+  it('should handle errors in JSON encoding', () => {
+    const invalidJson = '{"key": invalid}'
+    ;(jsonParse as jest.Mock).mockImplementation(() => {
+      throw new Error('Invalid JSON')
+    })
+    ;(basicLog.error as jest.Mock).mockImplementation(() => {})
+
+    expect(() => convertPayload(invalidJson, 'json', 'encode')).toThrow('Process.exit called with code 1')
+    expect(mockExit).toHaveBeenCalledWith(1)
+    expect(basicLog.error).toHaveBeenCalled()
+  })
+
+  it('should handle errors in CBOR encoding', () => {
+    const invalidCbor = '{"key": "value"}'
+    ;(cbor.encodeOne as jest.Mock).mockImplementation(() => {
+      throw new Error('Invalid CBOR')
+    })
+    ;(basicLog.error as jest.Mock).mockImplementation(() => {})
+
+    expect(() => convertPayload(invalidCbor, 'cbor', 'encode')).toThrow('Process.exit called with code 1')
+    expect(mockExit).toHaveBeenCalledWith(1)
+    expect(basicLog.error).toHaveBeenCalled()
+  })
+
+  it('should use default behavior when format is undefined', () => {
+    const input = 'Hello, MQTT!'
+    const buffer = Buffer.from(input)
+
+    const decodeResult = convertPayload(buffer)
+    expect(decodeResult).toBe(input)
+
+    const encodeResult = convertPayload(input, undefined, 'encode')
+    expect(encodeResult).toEqual(buffer)
+
+    expect(jsonParse).not.toHaveBeenCalled()
+    expect(jsonStringify).not.toHaveBeenCalled()
+  })
+})