Use Assert.state improve code readability

[dukbong]

This PR is expected to improve code readability by using the Assert.state() method.

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[mp911de]

Thank you for your contribution. That's merged, fixed, polished, and backported now.

Assert method usage triggers exceptions if the condition evaluates to false. That has required to flip the condition. Please mind running tests/the build before submitting a pull request.

[dukbong]

Thank you for your contribution. That's merged, fixed, polished, and backported now.

I'm so sorry....
I will make testing a habit to avoid such incidents in the future.....