Overview

Scriptorium.Nib is the assertion layer for the Scriptorium family.

It works with any F# framework — or directly in application code.

Installation

dotnet add package Scriptorium.Nib

Usage

All assertions follows a consistent pattern:

1. Start with assertThat
2. Pass subject to validate
3. Chain of assertions

Basic assertions

open Scriptorium.Nib.Assertion

assertThat 42 (isEqualTo 42)
assertThat "hello" (isNotEqualTo "world")
assertThat true isTrue

Compositions

Assertions compose with >>

Tip

You can read >> as and

assertThat 42 (isGreaterThan 0 >> isLessThan 100 >> isNotEqualTo 99)

Every assertion in the chain runs — failures are collected and reported together rather than stopping on the first one.

Nested assertions

Use inside and tag to drill into records and label failures:

assertThat
    {
        Name = ""
        Age = 15
    }
    (inside _.Name (tag "name" >> isNotEqualTo "")
     >> inside _.Age (tag "age" >> isGreaterOrEqual 18))

// Throws:
//   [name] given "" should not be equal to ""
//   [age] given 15 should be greater than or equal to 18

Collections, options, and results have dedicated assertions:

assertThat
    [
        1
        2
        3
    ]
    (isNotEmpty >> hasSize 3 >> contain 2)

assertThat (Some "alice") (Option.value >> isNotEqualTo "")

assertThat (Ok 42: Result<int, string>) (Result.okValue >> isGreaterThan 0)