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The Anatomy of a mocked call - RuLu 2014
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Penelope Phippen
June 18, 2014
Technology
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The Anatomy of a mocked call - RuLu 2014
Penelope Phippen
June 18, 2014
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Transcript
The Anatomy of a mocked call
!/samphippen
Hello everyone :)
Why is testing?
x`
None
Tests force behaviour
Without tests Anything could happen
Unit Testing makes me happy :)
Stubbing and mocking
Stubbing
Fake response to a method
allow(x).to( receive(:foo).and_return(3) )
x.foo will return 3
Mocking
Testing methods get called
expect(x).to receive(:foo)
Test fails if x does not receive foo
expect(x).to receive(:foo).with(3)
expect(x).to( receive(:foo) .with(3) .exactly(4).times )
How does it work?
Stubs
it “does something” do allow(foo).to receive(:bar) expect(foo.bar).to eq(nil) end
it “does something” do allow(foo).to receive(:bar) expect(foo.bar).to eq(nil) end
allow is syntax sugar for AllowanceTarget.new
Allowance Target
Allowance Target TargetBase
AllowanceTarget calls #delegate_to with :setup_allowance on TargetBase
Allowance Target TargetBase
TargetBase defines #to on AllowanceTarget
Defined #to calls :setup_allowance on matchers passed to #to
Allowance Target TargetBase
it “does something” do allow(foo).to receive(:bar) expect(foo.bar).to eq(nil) end
Things passed to #to are called “matchers”
Receive is a commonly used mocking/stubbing matcher
AllowanceTarget#to calls setup_allowance on the passed matcher
Allowance Target TargetBase Allowance Target TargetBase Receive
Receive#setup_allowance creates a Mock Proxy for object
Receive#setup_allowance calls #add_stub on the Mock Proxy
Allowance Target TargetBase Receive Proxy
Proxy objects manage all mocks/stubs for an object
it “does something” do allow(foo).to receive(:bar) allow(foo).to receive(:baz) expect(foo.bar).to eq(nil)
end
Proxy#add_stub creates a MethodDouble for the stubbed method
Allowance Target TargetBase Proxy Receive Method Double
MethodDouble saves the original implementation
MethodDouble creates stub implementation
it “does something” do allow(foo).to receive(:bar) expect(foo.bar).to eq(nil) end
it “does something” do allow(foo).to receive(:bar) expect(foo.bar).to eq(nil) end
foo.bar is the stubbed implementation
Call foo.bar
Method Double Call foo.bar
Method Double Call foo.bar Proxy
Method Double Call foo.bar Proxy Invokes stub
Method Double Call foo.bar Proxy Invokes stub Return value
it “does something” do allow(foo).to receive(:bar) expect(foo.bar).to eq(nil) end
RSpec manages lifecycle of mocks
RSpec::Mocks.setup
RSpec::Mocks.setup Your test
RSpec::Mocks.setup Your test RSpec::Mocks.verify
RSpec::Mocks.teardown RSpec::Mocks.setup Your test RSpec::Mocks.verify
All of this happens in a mock space
Allowance Target TargetBase Proxy Receive Method Double
RSpec::Mocks.teardown calls #reset_all on the current Space
Space#reset_all calls #reset on each proxy
Proxy#reset calls #reset on each MethodDouble
MethodDouble#reset returns original methods to objects
RSpec::Mocks.teardown RSpec::Mocks.setup Your test RSpec::Mocks.verify
Phew
Mocks
it “does something” do expect(foo).to receive(:bar).with(3) expect(foo.bar(3)).to eq(nil) end
expect is syntax sugar for ExpectationTarget.new
Expectation Target TargetBase Proxy Receive Method Double
Calls #setup_expectation
it “does something” do expect(foo).to receive(:bar).with(3) expect(foo.bar(3)).to eq(nil) end
Receive stores details of stubbed/ mocked implementation
Expectation Target TargetBase Proxy Receive Method Double
Method Double Call foo.bar Proxy Invokes stub Return value
Proxy callback checks arguments
Proxy raises if args don’t match
it “does something” do expect(foo).to receive(:bar).with(3) expect(foo.bar(3)).to eq(nil) end
RSpec::Mocks.teardown RSpec::Mocks.setup Your test RSpec::Mocks.verify
RSpec::Mocks.verify calls Space#verify_all
Space#verify_all calls #verify on each Proxy
Proxy raises if mock not called
And that’s how it all works :)
RSpec::Mocks.teardown RSpec::Mocks.setup Your test RSpec::Mocks.verify
expect(x).to receive(:foo) allow(x).to receive(:foo)
Target TargetBase
expect(x).to receive(:foo) allow(x).to receive(:foo)
Target TargetBase
expect(x).to receive(:foo) allow(x).to receive(:foo)
Receive
Proxy Receive
Proxy Receive Method Double
Target TargetBase Proxy Receive Method Double
Method Double Call foo.bar Proxy Invokes stub Return value
Target TargetBase Proxy Receive Method Double
RSpec 3.0.0 is out Please use it
tinyurl.com/ samrl2014
Let’s have some questions !/samphippen sam@funandplausible.com