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In the course of developing and testing various components for working with Puppet, I had a particularly difficult time with stubbing calls to other Ruby objects outside of my control.
After a ridiculous amount of searching, I finally found the answer that made the whole process seamless.
In general, when testing, you really don’t want to stub out methods on objects that you don’t actually control. However, when you’re testing components that explicitly deal with system interactions, you’re going to run into numerous cases where this simply isn’t tenable.
The code that I was wrangling with was a Puppet Fact called login_defs that
simply read the contents of /etc/login.defs and converted it into a
reasonable Hash for processing by other Ruby code.
As you may expect, I had the following call in my code
login_defs_content = File.read('/etc/login.defs')The logical method for testing this is something like the following:
describe 'custom fact login_defs' do
before(:each) do
Facter.clear
end
context 'when reading /etc/login.defs' do
let(:login_defs_content) { <<-EOM
UID_MIN 1000
UID_MAX 60000
EOM
}
it 'should return hash values from /etc/login.defs' do
File.expects(:read).with('/etc/login.defs').returns(login_defs_content)
expect(Facter.fact('login_defs').value).to eq({
'uid_min' => 1000,
'uid_max' => 60000
})
end
end
endUnfortunately, when the code above is executed, something else is almost
guaranteed to call File.read at some point and, regardless of the with
statement, you’ll end up with an Unexpected Invocation error from Mocha.
Honestly, while this does not work the way that I expects, it works how it works and there’s not much that I could find to do about the default behavior.
Honestly, I stumbled across this solution somewhere online (If I find it again, I’ll cite it here), and realized that I really needed to get this recorded so that I could find it again in the future.
To make stubs work generally how you would expect, you need to have an
associated statement similar to the following that essentially stubs all other
matching calls and ignores them.
File.stubs(:read).with(Not(equals('/etc/login.defs')))Now, this may have unintended side effects but, so long as your tests are well confined, there should be no issue in general.
The resulting code would looks something like the following:
describe 'custom fact login_defs' do
before(:each) do
Facter.clear
end
context 'when reading /etc/login.defs' do
let(:login_defs_content) { <<-EOM
UID_MIN 1000
UID_MAX 60000
EOM
}
it 'should return hash values from /etc/login.defs' do
File.expects(:read).with('/etc/login.defs').returns(login_defs_content)
File.stubs(:read).with(Not(equals('/etc/login_defs')))
expect(Facter.fact('login_defs').value).to eq({
'uid_min' => 1000,
'uid_max' => 60000
})
end
end
end
Trevor has worked in a variety of IT fields over the last
decade, including systems engineering, operating system
automation, security engineering, and various levels of
development.
At OP his responsibilities include maintaining overall
technical oversight for Onyx Point solutions, providing
technical leadership and mentorship to the DevOps teams. He is
also responsible for leading OP’s solutions and intellectual
property development efforts, setting the technical focus of
the company, and managing OP products and related services. In
this regard, he oversees product development and delivery as
well as developing the strategic roadmap for OP’s product line.
At Onyx Point, our engineers focus on Security, System Administration, Automation, Dataflow, and DevOps consulting for government and commercial clients. We offer professional services for Puppet, RedHat, SIMP, NiFi, GitLab, and the other solutions in place that keep your systems running securely and efficiently. We offer Open Source Software support and Engineering and Consulting services through GSA IT Schedule 70. As Open Source contributors and advocates, we encourage the use of FOSS products in Government as part of an overarching IT Efficiencies plan to reduce ongoing IT expenditures attributed to software licensing. Our support and contributions to Open Source, are just one of our many guiding principles