Book Image

Mastering Clojure

By : Akhil Wali
Book Image

Mastering Clojure

By: Akhil Wali

Overview of this book

Clojure is a general-purpose language from the Lisp family with an emphasis on functional programming. It has some interesting concepts and features such as immutability, gradual typing, thread-safe concurrency primitives, and macro-based metaprogramming, which makes it a great choice to create modern, performant, and scalable applications. Mastering Clojure gives you an insight into the nitty-gritty details and more advanced features of the Clojure programming language to create more scalable, maintainable, and elegant applications. You’ll start off by learning the details of sequences, concurrency primitives, and macros. Packed with a lot of examples, you’ll get a walkthrough on orchestrating concurrency and parallelism, which will help you understand Clojure reducers, and we’ll walk through composing transducers so you know about functional composition and process transformation inside out. We also explain how reducers and transducers can be used to handle data in a more performant manner. Later on, we describe how Clojure also supports other programming paradigms such as pure functional programming and logic programming. Furthermore, you’ll level up your skills by taking advantage of Clojure's powerful macro system. Parallel, asynchronous, and reactive programming techniques are also described in detail. Lastly, we’ll show you how to test and troubleshoot your code to speed up your development cycles and allow you to deploy the code faster.
Table of Contents (19 chapters)
Mastering Clojure
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
References
Index

Writing tests


Being a thoughtfully designed language, Clojure has a built-in unit testing library, namely clojure.test. Apart from that, there are a couple constructs in the core language that are helpful with regard to testing. Of course, these constructs don't allow us to define and run any tests in the formal sense, and the constructs from the clojure.test namespace must be preferred for that purpose.

Let's start off by briefly discussing the constructs from the core language that can be used for unit testing. The assert function checks whether an expression evaluates to a truthy value at runtime. This function will throw an exception if the expression passed to it does not evaluate to a truthy value, and the message of this exception can be optionally specified as a second argument to the assert form. We can effectively disable all the assert forms in a given program by using the global *assert* compile time var. This variable can only be changed by a top-level set! form in a given program...