Require

A simple lightweight fluent assertion library.

Features

Fully tested
Readable error messages
Correct argument exceptions based on assertion type
Fluent api for simple "one-liner" assertions
Map to destination type assuming validity
Implicit assignment
Easily plug in your favourite validation or add custom validators

Why?

Yes, other libraries exist. Sometimes you just need something stupidly simple to use. There is a Guard Class in modern versions of .NET but it isn't fluent. FluentAssertions is great but is arguably much more than you need for simple things.

Getting Started

All the methods stem from the calling a static assertion on the Requires class. From there, simply chain further assertion calls. Every method has a corresponding And{Method} for chaining.

If an assertion fails, an exception is thrown. If not, you can assume it's valid.

Usage

// Validate the response with implicit assignment back to the target type
string value = Requires.NotNull("")
    .AndNotDefault(); // Look ma, no param!

// Map data post-assertion using Map method
string unwrappedValue = Requires.NotNull(new Example("NestedValue"))
    .Map(v => v.NestedProp);
    
// Then will only be called if all assertions pass
Requires.NotNull(new Example("NestedValue"))
    .Then(v => { /* Ah! This feels like JavaScript! */ });

Note: There are many other assertion methods available for object references, strings, ints, decimals,IEnumberables etc. Missing something? See advanced usage and contribution guidelines.

Advanced Usage

"Advanced" seems a bit much - this isn't rocket-science. However, if you're missing an assertion method, all is not lost! You have a couple options without needing to break out of the fluent assertion chain.

Pro Tip: These are also a cool way to integrate the built in Guard class methods

Generic `And` Fallback

// This will throw if the value is equal to "bucket of cheese"
Require.NotNull("").And(v => v != "bucket of cheese")

Extension Method

public static FluentRequireResult<string> AndNotBucketOfCheese(this FluentRequireResult<string> fluentResult) => fluentResult.Value != "bucket of cheese"

Contributing/Questions

Please create an issue for any questions, bugs and feature requests.

Roadmap

Things I'd like to do:

Separate each method into it's own file so that Requires isn't so big
Separate each method's tests into it's own file too

Lukejkw/Require