There is another F# assertion library that is completely different from FsUnit but with different design philosophies accomplishes the same thing, by making F# unit tests more functional. Just like FsUnit, this library provides the means of writing assertions, but relies on NUnit as a testing framework.

Instead of working with a DSL like FsUnit or API such as with the NUnit framework, the Unquote library assertions are based on F# code quotations.

Code quotations is a quite unknown feature of F# where you can turn any code into an abstract syntax tree. Namely, when the F# compiler finds a code quotation in your source file, it will not compile it, but rather expand it into a syntax tree that represents an F# expression.

The following is an example of a code quotation:

<@ 1 + 1 @>

If we execute this in F# Interactive, we'll get the following output:

val it : Quotations.Expr =
  Call (None, op_Addition, [Value (1), Value (1)])

This is truly code as data, and we can use it to write...