Add minimum length validator.

Author: CodingFlow

CodingFlow.FluentValidation.UnitTests/MinimumLengthValidatorTests.cs

@@ -0,0 +1,37 @@
+using CodingFlow.FluentValidation.Validators;
+using FluentAssertions;
+using static CodingFlow.FluentValidation.Validations;
+
+namespace CodingFlow.FluentValidation.UnitTests;
+
+public class MinimumLengthValidatorTests
+{
+    [TestCase("short")]
+    [TestCase("long string")]
+    public void MinimumLength_Valid(string input)
+    {
+        var result = RuleFor(input)
+            .MinimumLength(5)
+            .Result();
+
+        result.Should().BeEquivalentTo(new ValidationResult
+        {
+            IsValid = true,
+            Errors = []
+        });
+    }
+
+    [TestCase("four")]
+    public void MinimumLength_Invalid(string input)
+    {
+        var result = RuleFor(input)
+            .MinimumLength(5)
+            .Result();
+
+        result.Should().BeEquivalentTo(new ValidationResult
+        {
+            IsValid = false,
+            Errors = [new() { Message = $"Value '{input}' has a length less than 5." }]
+        });
+    }
+}

CodingFlow.FluentValidation/Validators/MinimumLengthValidator.cs

@@ -0,0 +1,27 @@
+namespace CodingFlow.FluentValidation.Validators;
+
+public static class MinimumLengthValidator
+{
+    /// <summary>
+    /// Ensures the string has a length that is at least as long as a minimum.
+    /// </summary>
+    /// <typeparam name="T">Input type.</typeparam>
+    /// <param name="validation"></param>
+    /// <param name="input">String to check length.</param>
+    /// <param name="minimum">Minimum length of the string.</param>
+    /// <returns></returns>
+    public static FluentValidation<string> MinimumLength(this FluentValidation<string> validation, int minimum)
+    {
+        Validate(validation, minimum);
+
+        return validation;
+    }
+
+    private static void Validate(FluentValidation<string> validation, int minimum)
+    {
+        validation.Validate(
+            validation => validation.Input.Length >= minimum,
+            new ValidationError($"Value '{validation.Input}' has a length less than {minimum}.")
+        );
+    }
+}

Examples/MinimumLengthExample.cs

@@ -0,0 +1,18 @@
+using CodingFlow.FluentValidation.Validators;
+using static CodingFlow.FluentValidation.Validations;
+
+namespace Examples;
+
+internal class MinimumLengthExample
+{
+    public void Run()
+    {
+        var input = "some string";
+
+        // begin-snippet: MinimumLengthExample
+        RuleFor(input)
+            .MinimumLength(5) // Must be at least 5 characters long.
+            .Result();
+        // end-snippet
+    }
+}

README.md

@@ -106,6 +106,20 @@ RuleFor(input)
 <sup><a href='/Examples/EqualBasicExample.cs#L12-L16' title='Snippet source file'>snippet source</a> | <a href='#snippet-EqualBasicExample' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
+## MinimumLength Validator
+
+Ensures the string has a minimum length.
+
+<!-- snippet: MinimumLengthExample -->
+<a id='snippet-MinimumLengthExample'></a>
+```cs
+RuleFor(input)
+    .MinimumLength(5) // Must be at least 5 characters long.
+    .Result();
+```
+<sup><a href='/Examples/MinimumLengthExample.cs#L12-L16' title='Snippet source file'>snippet source</a> | <a href='#snippet-MinimumLengthExample' title='Start of snippet'>anchor</a></sup>
+<!-- endSnippet -->
+
 ## Regular Expression Validator
 
 Aka `Matches`, ensure the string passes a regular expression test.

README.source.md

@@ -47,6 +47,12 @@ Ensures the input is considered equal to the provided value. For reference types
 
 snippet: EqualBasicExample
 
+## MinimumLength Validator
+
+Ensures the string has a minimum length.
+
+snippet: MinimumLengthExample
+
 ## Regular Expression Validator
 
 Aka `Matches`, ensure the string passes a regular expression test.