WRITING CUSTOM RSPEC MATCHERS

Custom RSpec matchers can help with this problem. ArgumentError – occures, but there might be edge cases where you want to pass the exception to the user. Note that we can change the block argument names to match our domain. This should demonstrate the difference between a generic, re-usable matcher to hide implementation details from the reader of the code, and modelling your domain language so you can write human-friendly specifications. This gave us the opportunity to use the much terser ternary operator and split out the fetching of the status code from the matcher comparison.

Make sure your matcher returns either true or false. Home Feed About Archives github twitter. I believe you should start writing custom matchers as soon as possible in a project. You should handle each StandardError with care! You might argue that this matcher is not quite high-level enough to actually model our domain.

Note that we can change the block argument names to match our domain.

writing custom rspec matchers

We can therefore create a new file. It all boils down to coming up with a true or false response to indicate whether the test passed or failed.

writing custom rspec matchers

It therefore needs to be well-factored and use the domain language. This helps you build a suite of easily re-usable cusfom that the entire team can use.

RSpec dumps the actual and expected values and combines them with the name of our matcher to create a generic error message.

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Define a custom matcher – Custom matchers – RSpec Expectations – RSpec – Relish

We could write the above matcher as a class as follows:. Our matcher is quite useful, but we could make it neater. To add a collaborator to this project you will need to use the Relish gem to add the collaborator via a terminal command.

We want to assert that sensitive information is omitted from the JSON document for unauthorised users. Note that we can change the block argument names to match our domain.

You might argue that this matcher is not quite high-level enough to actually model our domain. Next post Previous post. Close To add a collaborator to this project you will need to use the Relish gem to add the collaborator via a terminal command.

writing custom rspec matchers

The specs are fair enough, but there are two different levels of abstraction in play here: We can improve our matcher further with a custom exception message. This example has only demonstrated the basics of RSpec matchers. This example has only demonstrated the basics of RSpec matchers.

Behind the scenes RSpec:: Defining Custom Matchers in RSpec Defining custom RSpec matchers is really easy and a great way to increase the readability of your tests. Which is not as nice as with our DSL -version. ArgumentError – occures, but there might be edge cases where you want to pass the exception to the user.

If you need to write a more complex matcher and would like to use the Class -approach yourself, please head over to our API -documentation and read the docs about the MatcherProtocol.

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We want to assert that sensitive information is omitted from the XML for unauthorised users.

We can introduce a helper method to make things pretty again:. Test rspfc is code like any other code, which needs to be maintained. However, the APIs can differ e. Define a custom matcher rspec-expectations provides a DSL for defining custom matchers. It therefore needs to be readable and DRY.

How to Use Custom RSpec Matchers to Specify Behaviour

Custom RSpec matchers can help with this problem. Our matcher is basically ready for use, but we can do better. To get into this habit, try to limit yourself to a maximum of three lines per test: You should handle each StandardError with care! The DSL-version looked much better. Defining custom RSpec matchers is rspce easy and a great way to increase the readability of your tests.

First comes the expected value, second the actual one.