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Write F# unit test assertions as quoted expressions, get step-by-step failure messages for free


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Unquote is not just another DSL or API for making unit test assertions. Instead, assertions are written as plain, statically-checked F# quoted expressions and test failure messages are given as step-by-step F# expression evaluations.

Unquote integrates configuration-free with all exception-based unit testing frameworks including, NUnit, MbUnit, Fuchu, and MSTest. For example, the following failing test

let ``demo Unquote xUnit support`` () =
    test <@ [3; 2; 1; 0] |> ((+) 1) = [1 + 3..1 + 0] @>

produces the following failure message

Test 'Module.demo Unquote xUnit support' failed: 

[3; 2; 1; 0] |> ((+) 1) = [1 + 3..1 + 0]
[4; 3; 2; 1] = [4..1]
[4; 3; 2; 1] = []

	C:\File.fs(28,0): at Module.demo Unquote xUnit support()

Unquote may even be used within FSI sessions, enabling the direct migration of ad-hoc FSI tests during interactive development to formal test suites.

In addition to test : Quotations.Expr<bool> -> unit used for performing most assertions, Unquote has convenience operators =!, >!, <!, >=!, <=!, and <>! for performing simple comparison assertions. And finally, Unquote has operators raises<'a when 'a :> exn> : Quotations.Expr -> unit and raisesWith : Expr -> (#exn -> Expr<bool>) -> unit for asserting whether a quoted expression raises an expected exception.

At the heart of Unquote, are (public) operators for decompiling, evaluating, and incrementally reducing F# Quotations. Unquote can decompile many F# quoted expressions as single line, non-light syntax strings. See Decompiler Features for a list of notable decompiler features.

The incremental evaluator performs reduction steps until a non-reducible expression is reached. During a reduction step, an expression will be reduced if all of its subexpressions are already reduced, recursively reducing the sub-expressions otherwise. Hence order of evaluation is not strictly adhered to, but shouldn't be a problem in practice since assertion expressions are not expected to depend on order of evaluation side effects. Except for sequential expressions, which are evaluated from left to right, and control structures and boolean operator expressions, which follow valid branch paths and short-circuiting rules. If a test expression throws an exception, the test will fail and print each reduction step up to the point of the exception, and then print the exception.

To learn more about how to use Unquote, see User Guide

To learn about how you can contribute to Unquote's development, see Contributing

Unquote was originally inspired by Groovy Power Asserts.

You are welcome to Pay What You Want for Unquote via PayPal.

Copyright 2011-2024 Swensen Software


Write F# unit test assertions as quoted expressions, get step-by-step failure messages for free







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