Failure on the expect statement when comparing numbers in Jest..."The Jest magic number comparison is

I am currently conducting a test to verify that the magic number of a Buffer is in zip format.

This involves extracting the first 4 bytes of the buffer into a string and comparing it with the magic number for zip, which is PK.

   const zipMagicNumber: string = 'PK'
   const uploadedMagicNumber: string = uploadMock.mock.calls[0][0].Body.subarray(0, 4).toString()

   expect(zipMagicNumber).toBe(uploadedMagicNumber)

However, the test is failing with the following error:

    expect(received).toBe(expected) // Object.is equality

    Expected: "PK"
    Received: "PK"

Both values are the same and they are both strings. I'm unsure what might be causing this issue. Can anyone help me identify the problem?

typescriptjestjsmagic-numbers

Answer №1

After discovering hidden characters causing a comparison error, I decided to switch to hex comparisons for better readability. This adjustment resolved the issue:

const zipMagicNumber = Buffer.from('504B0304', 'hex').toString('hex')
const uploadedMagicNumber = uploadMock.mock.calls[0][0].Body.subarray(0, 4).toString('hex')

expect(zipMagicNumber).toBe(uploadedMagicNumber)

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