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rubymockingtestunit

How do I mock or override Kernel.system?

How would be the correct way to mock or override the Kernel.system method so that when called with:

system("some command")

instead of executing the command, it executes some predefined code?

I tried adding the following to my Test class:

module Kernel
    def system
        puts "SYSTEM CALL!!"
    end
end

But it did not work as expected, instead, the system call was run when executing a test.

Solution

  • If you are talking about unit tests and use Rspec, you should be able to do it like this:

    Kernel.should_receive(:system)

    or a little more loose:

    Kernel.stub(:system)

    More info: https://www.relishapp.com/rspec/rspec-mocks/v/2-13/docs/message-expectations/expect-a-message