Convert tests to Pest

- Update deps

.gitignore

@@ -1,2 +1,3 @@
 .idea
 vendor
+*-tests.txt

README.md

@@ -7,24 +7,31 @@ This project contains PHP utility classes whose functionality is inspired by the
 This early-stage library currently provides two classes, both of which are designed to wrap values and indicate the state of the action that produced them. `Option<T>` represents a variable that may or may not have a value. `Result<TOK, TError>` represents the result of an action; the "ok" and "error" states both provide a value.
 
 |                                                   | `Option<T>`<br>Replaces `null` checks                 | `Result<TOK, TError>`<br>Replaces exception-based error handling            |
-|----------------------------------------------------|--------------------------------------------------------------------------------|------------------------------------------------------------------|
+|---------------------------------------------------|-------------------------------------------------------|-----------------------------------------------------------------------------|
-| **Creating**                                       | `::Some(T)` for Some<br>`::None()` for None<br>`::of($value)` _None if `null`_ | `::OK(TOK)` for OK<br>`::Error(TError)` for Error                |
+| **Creating**                                      | `::Some(T)` for Some                                  | `::OK(TOK)` for OK                                                          |
-| **Querying**                                       | `->isSome()`<br>`->isNone()`                                                   | `->isOK()`<br>`->isError()`                                      |
+|                                                   | `::None()` for None                                   | `::Error(TError)` for Error                                                 |
-| **Reading**<br>_throws if called on missing value_ | `->get()`                                                                      | `->getOK()`<br>`->getError()`                                    |
+|                                                   | `::of($value)` _None if `null`_                       |                                                                             |
-| **Transforming**<br>_still `Option` or `Result`_   | `->map(callable(T): U)`                                                        | `->map(callable(TOK): U)`<br>`->mapError(callable(TError): U)`   |
+| **Querying**                                      | `->isSome(): bool`                                    | `->isOK(): bool`                                                            |
-| **Iterating**                                      | `->iter(callable(T): void)`                                                    | `->iter(callable(TOK): void)`                                    |
+|                                                   | `->isNone(): bool`                                    | `->isError(): bool`                                                         |
-| **Inspecting**<br>_returns the original instance_  | `->tap(callable(Option<T>): void)`                                             | `->tap(callable(Result<TOK, TError>): void)`                     |
+|                                                   | `->contains(T, $strict = true): bool`                 | `->contains(TOK, $strict = true): bool`                                     |
+|                                                   | `->exists(callable(T): bool): bool`                   | `->exists(callable(TOK): bool): bool`                                       |
+| **Reading**<br>                                   | `->get(): T`                                          | `->getOK(): TOK`                                                            |
+| _all throw if called on missing value_            |                                                       | `->getError(): TError`                                                      |
+| **Transforming**<br>                              | `->map(callable(T): TMapped): Option<TMapped>`        | `->map(callable(TOK): TMapped): Result<TMapped, TError>`                    |
+| _all still `Option` or `Result`_                  |                                                       | `->mapError(callable(TError): TMapped): Result<TOK, TMapped>`               |
+| **Iterating**                                     | `->iter(callable(T): void): void`                     | `->iter(callable(TOK): void): void`                                         |
+| **Inspecting**<br>_returns the original instance_ | `->tap(callable(Option<T>): void): Option<T>`         | `->tap(callable(Result<TOK, TError>): void): Result<TOK, TError>`           |
+| **Continued Processing**                          | `->bind(callable(T): Option<TBound>): Option<TBound>` | `->bind(callable(TOK): Result<TBoundOK, TError>): Result<TBoundOK, TError>` |
+| **Changing Types**                                | `->toArray(): T[]`                                    | `->toArray(): TOK[]`                                                        |
+|                                                   |                                                       | `->toOption(): Option<TOK>`                                                 |
 
 In addition to this, `Option<T>` provides:
 - `->getOrDefault(T)` will return the Some value if it exists or the given default if the option is None.
 - `->getOrCall(callable(): mixed)` will call the given function if the option is None. That function may return a value, or may be `void` or `never`.
+- `->getOrThrow(callable(): Exception)` will return the Some value if it exists, or throw the exception returned by the function if the option is None.
 - `->filter(callable(T): bool)` will compare a Some value against the callable, and if it returns `true`, will remain Some; if it returns `false`, the value will become None.
-- `->is(T, $strict = true)` will return `true` if the option is Some and the value matches. Strict equality (the default) uses `===` for the comparison; if strict is set to `false`, the comparison will use `==` instead.
 - `->unwrap()` will return `null` for None options and the value for Some options.
 
-`Result<TOK, TError>` also provides:
-- `toOption()` will transform an OK result to a Some option, and an Error result to a None option.
-
 Finally, we would be remiss to not acknowledge some really cool prior art in this area - the [PhpOption](https://github.com/schmittjoh/php-option) project. `Option::of` recognizes their options and converts them properly, and `Option<T>` instances have a `->toPhpOption()` method that will convert these back into PhpOption's `Some<T>` and `None` instances. There is also a [ResultType](https://github.com/GrahamCampbell/Result-Type) project from the same team, though this project's result does not (yet) have any conversion methods for it.
 
 ## The Inspiration

composer.json

@@ -17,11 +17,11 @@
     "rss": "https://git.bitbadger.solutions/bit-badger/inspired-by-fsharp.rss"
   },
   "require": {
-    "php": "^8.2"
+    "php": "8.2 - 8.3"
   },
   "require-dev": {
-    "phpunit/phpunit": "^11",
+    "phpoption/phpoption": "^1",
-    "phpoption/phpoption": "^1"
+    "pestphp/pest": "^3.5"
   },
   "autoload": {
     "psr-4": {
@@ -30,10 +30,15 @@
   },
   "autoload-dev": {
     "psr-4": {
-      "Test\\": "./tests"
+      "Tests\\": "./tests"
     }
   },
   "archive": {
     "exclude": [ "/tests", "/.gitattributes", "/.gitignore", "/.git", "/composer.lock" ]
+  },
+  "config": {
+    "allow-plugins": {
+      "pestphp/pest-plugin": true
+    }
   }
 }

phpunit.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.3/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         colors="true"
+>
+    <testsuites>
+        <testsuite name="Test Suite">
+            <directory suffix="Test.php">./tests</directory>
+        </testsuite>
+    </testsuites>
+    <source>
+        <include>
+            <directory suffix=".php">./src</directory>
+        </include>
+    </source>
+</phpunit>

src/Option.php

@@ -10,6 +10,7 @@ declare(strict_types=1);
 namespace BitBadger\InspiredByFSharp;
 
 use Error;
+use Exception;
 use InvalidArgumentException;
 
 /**
@@ -84,21 +85,73 @@ readonly class Option
     /**
      * Get the value, or return the value of a callable function
      *
-     * @template U The return type of the callable provided
+     * @template TCalled The return type of the callable provided
-     * @param callable(): U $f The callable function to use for `None` options
+     * @param callable(): TCalled $f The callable function to use for `None` options
-     * @return T|mixed The value if `Some`, the result of the callable if `None`
+     * @return T|TCalled The value if `Some`, the result of the callable if `None`
      */
     public function getOrCall(callable $f): mixed
     {
         return $this->value ?? $f();
     }
 
+    /**
+     * Get the value, or throw the
+     * @param callable(): Exception $exFunc A function to construct the exception to throw
+     * @return T The value of the option if `Some`
+     * @throws Exception If the option is `None`
+     */
+    public function getOrThrow(callable $exFunc): mixed
+    {
+        return $this->value ?? throw $exFunc();
+    }
+
+    /**
+     * Bind a function to this option (railway processing)
+     *
+     * If this option is Some, the function will be called with the option's value. If this option is None, it will be
+     * immediately returned.
+     *
+     * @template TBound The type returned by Some in the bound function
+     * @param callable(T): Option<TBound> $f The function that will receive the Some value; can return a different type
+     * @return Option<TBound> The updated option if the starting value was Some, None otherwise
+     */
+    public function bind(callable $f): Option
+    {
+        return $this->isNone() ? $this : $f($this->get());
+    }
+
+    /**
+     * Does the option contain the given value?
+     *
+     * @param T $value The value to be checked
+     * @param bool $strict True for strict equality (`===`), false for loose equality (`==`); optional, default is true
+     * @return bool True if the value matches, false if not; `None` always returns false
+     */
+    public function contains(mixed $value, bool $strict = true): bool
+    {
+        return match (true) {
+            $this->isNone() => false,
+            default         => $strict ? $this->value === $value : $this->value == $value,
+        };
+    }
+
+    /**
+     * Does the value of the option match the given predicate function?
+     *
+     * @param callable(T): bool $f The function to determine whether the value matches
+     * @return bool True if the `Some` value matches the function, false otherwise
+     */
+    public function exists(callable $f): bool
+    {
+        return $this->isSome() ? $f($this->value) : false;
+    }
+
     /**
      * Map this optional value to another value
      *
-     * @template U The type of the mapping function
+     * @template TMapped The type of the mapping function
-     * @param callable(T): U $f The mapping function
+     * @param callable(T): TMapped $f The mapping function
-     * @return Option<U> A `Some` instance with the transformed value if `Some`, `None` otherwise
+     * @return Option<TMapped> A `Some` instance with the transformed value if `Some`, `None` otherwise
      */
     public function map(callable $f): self
     {
@@ -125,25 +178,7 @@ readonly class Option
      */
     public function filter(callable $f): self
     {
-        return match (true) {
+        return $this->isNone() || $this->exists($f) ? $this : self::None();
-            $this->isNone() => $this,
-            default         => $f($this->value) ? $this : self::None(),
-        };
-    }
-
-    /**
-     * Does the option have the given value?
-     *
-     * @param T $value The value to be checked
-     * @param bool $strict True for strict equality (`===`), false for loose equality (`==`)
-     * @return bool True if the value matches, false if not; `None` always returns false
-     */
-    public function is(mixed $value, bool $strict = true): bool
-    {
-        return match (true) {
-            $this->isNone() => false,
-            default         => $strict ? $this->value === $value : $this->value == $value,
-        };
     }
 
     /**
@@ -168,6 +203,16 @@ readonly class Option
         return $this;
     }
 
+    /**
+     * Convert this option into a 0 or 1 item array
+     *
+     * @return T[] An empty array for `None`, a 1-item array for `Some`
+     */
+    public function toArray(): array
+    {
+        return $this->isSome() ? [$this->value] : [];
+    }
+
     /**
      * Convert this to a PhpOption option
      *

src/Result.php

@@ -87,12 +87,54 @@ readonly class Result
         return $this->errorValue->isSome();
     }
 
+    /**
+     * Bind a function to this result (railway processing)
+     *
+     * If this result is OK, the function will be called with the OK value of the result. If this result is Error, it
+     * will be immediately returned. This allows for a sequence of functions to proceed on the happy path (OK all the
+     * way), or be shunted off to the exit ramp once an error occurs.
+     *
+     * @template TBoundOK The type returned by OK in the bound function
+     * @param callable(TOK): Result<TBoundOK, TError> $f The function that will receive the OK value; can return a different type
+     * @return Result<TBoundOK, TError> The updated result if the function was successful, an error otherwise
+     */
+    public function bind(callable $f): Result
+    {
+        return $this->isError() ? $this : $f($this->getOK());
+    }
+
+    /**
+     * Does this result's "OK" value match the given value?
+     *
+     * @param TOK $value The value to be matched
+     * @param bool $strict True for strict equality (`===`), false for loose equality (`==`); optional, default is true
+     * @return bool True if the "OK" value matches the one provided, false otherwise
+     */
+    public function contains(mixed $value, bool $strict = true): bool
+    {
+        return match (true) {
+            $this->isError() => false,
+            default          => $this->okValue->contains($value, $strict),
+        };
+    }
+
+    /**
+     * Does the "OK" value of this result match the given predicate function?
+     *
+     * @param callable(TOK): bool $f The function to determine whether the value matches
+     * @return bool True if the OK value matches the function, false otherwise
+     */
+    public function exists(callable $f): bool
+    {
+        return $this->isOK() ? $f($this->okValue->get()) : false;
+    }
+
     /**
      * Map an `OK` result to another, leaving an `Error` result unmodified
      *
-     * @template U The type of the mapping function
+     * @template TMapped The type of the mapping function
-     * @param callable(TOK): U $f The mapping function
+     * @param callable(TOK): TMapped $f The mapping function
-     * @return Result<U, TError> A transformed `OK` instance or the original `Error` instance
+     * @return Result<TMapped, TError> A transformed `OK` instance or the original `Error` instance
      */
     public function map(callable $f): self
     {
@@ -102,9 +144,9 @@ readonly class Result
     /**
      * Map an `Error` result to another, leaving an `OK` result unmodified
      *
-     * @template U The type of the mapping function
+     * @template TMapped The type of the mapping function
-     * @param callable(TError): U $f The mapping function
+     * @param callable(TError): TMapped $f The mapping function
-     * @return Result<TOK, U> A transformed `Error` instance or the original `OK` instance
+     * @return Result<TOK, TMapped> A transformed `Error` instance or the original `OK` instance
      */
     public function mapError(callable $f): self
     {
@@ -123,6 +165,16 @@ readonly class Result
         }
     }
 
+    /**
+     * Convert this result into a 0 or 1 item array
+     *
+     * @return TOK[] An empty array for `Error`, a 1-item array for `OK`
+     */
+    public function toArray(): array
+    {
+        return $this->okValue->toArray();
+    }
+
     /**
      * Transform a `Result`'s `OK` value to an `Option`
      *

tests/OptionTest.php

@@ -1,295 +0,0 @@
-<?php
-/**
- * @author Daniel J. Summers <daniel@bitbadger.solutions>
- * @license MIT
- */
-
-declare(strict_types=1);
-
-namespace Test;
-
-use BitBadger\InspiredByFSharp\Option;
-use InvalidArgumentException;
-use PhpOption\{None, Some};
-use PHPUnit\Framework\Attributes\TestDox;
-use PHPUnit\Framework\TestCase;
-
-/**
- * Unit tests for the Option class
- */
-class OptionTest extends TestCase
-{
-    #[TestDox('Get succeeds for Some')]
-    public function testGetSucceedsForSome(): void
-    {
-        $it = Option::Some(9);
-        $this->assertTrue($it->isSome(), 'The option should have been "Some"');
-        $this->assertEquals(9, $it->get(), 'The value was incorrect');
-    }
-
-    #[TestDox('Get fails for None')]
-    public function testGetFailsForNone(): void
-    {
-        $this->expectException(InvalidArgumentException::class);
-        Option::None()->get();
-    }
-
-    #[TestDox('IsNone succeeds with None')]
-    public function testIsNoneSucceedsWithNone(): void
-    {
-        $this->assertTrue(Option::None()->isNone(), '"None" should return true');
-    }
-
-    #[TestDox('IsNone succeeds with Some')]
-    public function testIsNoneSucceedsWithSome(): void
-    {
-        $this->assertFalse(Option::Some(8)->isNone(), '"Some" should return false');
-    }
-
-    #[TestDox('IsSome succeeds with None')]
-    public function testIsSomeSucceedsWithNone(): void
-    {
-        $this->assertFalse(Option::None()->isSome(), '"None" should return false');
-    }
-
-    #[TestDox('IsSome succeeds with Some')]
-    public function testIsSomeSucceedsWithSome(): void
-    {
-        $this->assertTrue(Option::Some('boo')->isSome(), '"Some" should return true');
-    }
-
-    #[TestDox('GetOrDefault succeeds with None')]
-    public function testGetOrDefaultSucceedsWithNone(): void
-    {
-        $this->assertEquals('yes', Option::None()->getOrDefault('yes'), 'Value should have been default');
-    }
-
-    #[TestDox('GetOrDefault succeeds with Some')]
-    public function testGetOrDefaultSucceedsWithSome(): void
-    {
-        $this->assertEquals('no', Option::Some('no')->getOrDefault('yes'), 'Value should have been from option');
-    }
-
-    #[TestDox('GetOrCall succeeds with None')]
-    public function testGetOrCallSucceedsWithNone(): void
-    {
-        $value = Option::None()->getOrCall(new class { public function __invoke(): string { return 'called'; } });
-        $this->assertEquals('called', $value, 'The value should have been obtained from the callable');
-    }
-
-    #[TestDox('GetOrCall succeeds with Some')]
-    public function testGetOrCallSucceedsWithSome(): void
-    {
-        $value = Option::Some('passed')->getOrCall(
-            new class { public function __invoke(): string { return 'called'; } });
-        $this->assertEquals('passed', $value, 'The value should have been obtained from the option');
-    }
-
-    #[TestDox('Map succeeds with None')]
-    public function testMapSucceedsWithNone(): void
-    {
-        $tattle = new class { public bool $called = false; };
-        $none   = Option::None();
-        $mapped = $none->map(function () use ($tattle)
-        {
-            $tattle->called = true;
-            return 'hello';
-        });
-        $this->assertTrue($mapped->isNone(), 'The mapped option should be "None"');
-        $this->assertFalse($tattle->called, 'The mapping function should not have been called');
-        $this->assertSame($none, $mapped, 'The same "None" instance should have been returned');
-    }
-
-    #[TestDox('Map succeeds with Some')]
-    public function testMapSucceedsWithSome(): void
-    {
-        $mapped = Option::Some('abc ')->map(fn($it) => str_repeat($it, 2));
-        $this->assertTrue($mapped->isSome(), 'The mapped option should be "Some"');
-        $this->assertEquals('abc abc ', $mapped->get(), 'The mapping function was not called correctly');
-    }
-
-    #[TestDox('Map fails with Some when mapping is null')]
-    public function testMapFailsWithSomeWhenMappingIsNull(): void
-    {
-        $this->expectException(InvalidArgumentException::class);
-        Option::Some('oof')->map(fn($it) => null);
-    }
-
-    #[TestDox('Iter succeeds with None')]
-    public function testIterSucceedsWithNone(): void
-    {
-        $target = new class { public mixed $called = null; };
-        Option::None()->iter(function () use ($target) { $target->called = 'uh oh'; });
-        $this->assertNull($target->called, 'The function should not have been called');
-    }
-
-    #[TestDox('Iter succeeds with Some')]
-    public function testIterSucceedsWithSome(): void
-    {
-        $target = new class { public mixed $called = null; };
-        Option::Some(33)->iter(function ($it) use ($target) { $target->called = $it; });
-        $this->assertEquals(33, $target->called, 'The function should have been called with the "Some" value');
-    }
-
-    #[TestDox('Filter succeeds with None')]
-    public function testFilterSucceedsWithNone(): void
-    {
-        $tattle   = new class { public bool $called = false; };
-        $none     = Option::None();
-        $filtered = $none->filter(function () use ($tattle)
-        {
-            $tattle->called = true;
-            return true;
-        });
-        $this->assertTrue($filtered->isNone(), 'The filtered option should have been "None"');
-        $this->assertFalse($tattle->called, 'The callable should not have been called');
-        $this->assertSame($none, $filtered, 'The "None" instance returned should have been the one passed');
-    }
-
-    #[TestDox('Filter succeeds with Some when true')]
-    public function testFilterSucceedsWithSomeWhenTrue(): void
-    {
-        $some     = Option::Some(12);
-        $filtered = $some->filter(fn($it) => $it % 2 === 0);
-        $this->assertTrue($filtered->isSome(), 'The filtered option should have been "Some"');
-        $this->assertEquals(12, $filtered->get(), 'The filtered option value is incorrect');
-        $this->assertSame($some, $filtered, 'The same "Some" instance should have been returned');
-    }
-
-    #[TestDox('Filter succeeds with Some when false')]
-    public function testFilterSucceedsWithSomeWhenFalse(): void
-    {
-        $some     = Option::Some(23);
-        $filtered = $some->filter(fn($it) => $it % 2 === 0);
-        $this->assertTrue($filtered->isNone(), 'The filtered option should have been "None"');
-    }
-
-    #[TestDox('Is succeeds with None')]
-    public function testIsSucceedsWithNone(): void
-    {
-        $this->assertFalse(Option::None()->is(null), '"None" should always return false');
-    }
-
-    #[TestDox('Is succeeds with Some when strictly equal')]
-    public function testIsSucceedsWithSomeWhenStrictlyEqual(): void
-    {
-        $this->assertTrue(Option::Some(3)->is(3), '"Some" with strict equality should be true');
-    }
-
-    #[TestDox('Is succeeds with Some when strictly unequal')]
-    public function testIsSucceedsWithSomeWhenStrictlyUnequal(): void
-    {
-        $this->assertFalse(Option::Some('3')->is(3), '"Some" with strict equality should be false');
-    }
-
-    #[TestDox('Is succeeds with Some when loosely equal')]
-    public function testIsSucceedsWithSomeWhenLooselyEqual(): void
-    {
-        $this->assertTrue(Option::Some('3')->is(3, strict: false), '"Some" with loose equality should be true');
-    }
-
-    #[TestDox('Is succeeds with Some when loosely unequal')]
-    public function testIsSucceedsWithSomeWhenLooselyUnequal(): void
-    {
-        $this->assertFalse(Option::Some('3')->is(4, strict: false), '"Some" with loose equality should be false');
-    }
-
-    #[TestDox('Unwrap succeeds with None')]
-    public function testUnwrapSucceedsWithNone(): void
-    {
-        $this->assertNull(Option::None()->unwrap(), '"None" should return null');
-    }
-
-    #[TestDox('Unwrap succeeds with Some')]
-    public function testUnwrapSucceedsWithSome(): void
-    {
-        $this->assertEquals('boy howdy', Option::Some('boy howdy')->unwrap(), '"Some" should return its value');
-    }
-
-    #[TestDox('Tap succeeds with Some')]
-    public function testTapSucceedsWithSome(): void
-    {
-        $value    = '';
-        $original = Option::Some('testing');
-        $tapped   = $original->tap(
-            function (Option $it) use (&$value) { $value = $it->isSome() ? $it->get() : 'none'; });
-        $this->assertEquals('testing', $value, 'The tapped function was not called');
-        $this->assertSame($original, $tapped, 'The same option should have been returned');
-    }
-
-    #[TestDox('Tap succeeds with None')]
-    public function testTapSucceedsWithNone(): void
-    {
-        $value    = '';
-        $original = Option::None();
-        $tapped   = $original->tap(
-            function (Option $it) use (&$value) { $value = $it->isSome() ? $it->get() : 'none'; });
-        $this->assertEquals('none', $value, 'The tapped function was not called');
-        $this->assertSame($original, $tapped, 'The same option should have been returned');
-    }
-
-    #[TestDox('ToPhpOption succeeds for Some')]
-    public function testToPhpOptionSucceedsForSome(): void
-    {
-        $opt = Option::Some('php')->toPhpOption();
-        $this->assertNotNull($opt, 'The PhpOption should not have been null');
-        $this->assertInstanceOf('PhpOption\Some', $opt, 'The PhpOption should have been "Some"');
-        $this->assertTrue($opt->isDefined(), 'There should have been a value for the PhpOption');
-        $this->assertEquals('php', $opt->get(), 'The value was not correct');
-    }
-
-    #[TestDox('ToPhpOption succeeds for None')]
-    public function testToPhpOptionSucceedsForNone(): void
-    {
-        $opt = Option::None()->toPhpOption();
-        $this->assertNotNull($opt, 'The PhpOption should not have been null');
-        $this->assertInstanceOf('PhpOption\None', $opt, 'The PhpOption should have been "None"');
-        $this->assertFalse($opt->isDefined(), 'There should not have been a value for the PhpOption');
-    }
-
-    public function testSomeSucceedsWithValue(): void
-    {
-        $it = Option::Some('hello');
-        $this->assertTrue($it->isSome(), 'The option should have been "Some"');
-    }
-
-    public function testSomeFailsWithNull(): void
-    {
-        $this->expectException(InvalidArgumentException::class);
-        Option::Some(null);
-    }
-
-    public function testNoneSucceeds(): void
-    {
-        $it = Option::None();
-        $this->assertTrue($it->isNone(), 'The option should have been "None"');
-    }
-
-    public function testOfSucceedsWithNull(): void
-    {
-        $it = Option::of(null);
-        $this->assertTrue($it->isNone(), '"null" should have created a "None" option');
-    }
-
-    public function testOfSucceedsWithNonNull(): void
-    {
-        $it = Option::of('test');
-        $this->assertTrue($it->isSome(), 'A non-null value should have created a "Some" option');
-        $this->assertEquals('test', $it->get(), 'The value was not assigned correctly');
-    }
-
-    #[TestDox('Of succeeds with PhpOption\Some')]
-    public function testOfSucceedsWithPhpOptionSome(): void
-    {
-        $it = Option::of(Some::create('something'));
-        $this->assertTrue($it->isSome(), 'A "Some" PhpOption should have created a "Some" option');
-        $this->assertEquals('something', $it->get(), 'The value was not assigned correctly');
-    }
-
-    #[TestDox('Of succeeds with PhpOption\None')]
-    public function testOfSucceedsWithPhpOptionNone(): void
-    {
-        $it = Option::of(None::create());
-        $this->assertTrue($it->isNone(), 'A "None" PhpOption should have created a "None" option');
-    }
-}

tests/Pest.php

@@ -0,0 +1,45 @@
+<?php
+
+/*
+|--------------------------------------------------------------------------
+| Test Case
+|--------------------------------------------------------------------------
+|
+| The closure you provide to your test functions is always bound to a specific PHPUnit test
+| case class. By default, that class is "PHPUnit\Framework\TestCase". Of course, you may
+| need to change it using the "pest()" function to bind a different classes or traits.
+|
+*/
+
+// pest()->extend(Tests\TestCase::class)->in('Feature');
+
+/*
+|--------------------------------------------------------------------------
+| Expectations
+|--------------------------------------------------------------------------
+|
+| When you're writing tests, you often need to check that values meet certain conditions. The
+| "expect()" function gives you access to a set of "expectations" methods that you can use
+| to assert different things. Of course, you may extend the Expectation API at any time.
+|
+*/
+
+expect()->extend('toBeOne', function () {
+    return $this->toBe(1);
+});
+
+/*
+|--------------------------------------------------------------------------
+| Functions
+|--------------------------------------------------------------------------
+|
+| While Pest is very powerful out-of-the-box, you may have some testing code specific to your
+| project that you don't want to repeat in every file. Here you can also expose helpers as
+| global functions to help you to reduce the number of lines of code in your test files.
+|
+*/
+
+function something()
+{
+    // ..
+}

tests/ResultTest.php

@@ -1,223 +0,0 @@
-<?php
-/**
- * @author Daniel J. Summers <daniel@bitbadger.solutions>
- * @license MIT
- */
-
-declare(strict_types=1);
-
-namespace Test;
-
-use BitBadger\InspiredByFSharp\Result;
-use InvalidArgumentException;
-use PHPUnit\Framework\Attributes\TestDox;
-use PHPUnit\Framework\TestCase;
-
-/**
- * Unit tests for the Result class
- */
-class ResultTest extends TestCase
-{
-    #[TestDox('GetOK succeeds for OK result')]
-    public function testGetOKSucceedsForOKResult(): void
-    {
-        $result = Result::OK('yay');
-        $this->assertEquals('yay', $result->getOK(), 'The OK result should have been returned');
-    }
-
-    #[TestDox('GetOK fails for Error result')]
-    public function testGetOKFailsForErrorResult(): void
-    {
-        $this->expectException(InvalidArgumentException::class);
-        Result::Error('whoops')->getOK();
-    }
-
-    #[TestDox('GetError succeeds for Error result')]
-    public function testGetErrorSucceedsForErrorResult(): void
-    {
-        $result = Result::Error('boo');
-        $this->assertEquals('boo', $result->getError(), 'The Error result should have been returned');
-    }
-
-    #[TestDox('GetError fails for OK result')]
-    public function testGetErrorFailsForOKResult(): void
-    {
-        $this->expectException(InvalidArgumentException::class);
-        Result::OK('yeah')->getError();
-    }
-
-    #[TestDox('IsOK succeeds for OK result')]
-    public function testIsOKSucceedsForOKResult(): void
-    {
-        $result = Result::OK('ok');
-        $this->assertTrue($result->isOK(), 'The check for "OK" should have returned true');
-    }
-
-    #[TestDox('IsOK succeeds for Error result')]
-    public function testIsOKSucceedsForErrorResult(): void
-    {
-        $result = Result::Error('error');
-        $this->assertFalse($result->isOK(), 'The check for "OK" should have returned false');
-    }
-
-    #[TestDox('IsError succeeds for Error result')]
-    public function testIsErrorSucceedsForErrorResult(): void
-    {
-        $result = Result::Error('not ok');
-        $this->assertTrue($result->isError(), 'The check for "Error" should have returned true');
-    }
-
-    #[TestDox('IsError succeeds for OK result')]
-    public function testIsErrorSucceedsForOKResult(): void
-    {
-        $result = Result::OK('fine');
-        $this->assertFalse($result->isError(), 'The check for "Error" should have returned false');
-    }
-
-    #[TestDox('Map succeeds for OK result')]
-    public function testMapSucceedsForOKResult(): void
-    {
-        $ok     = Result::OK('yard');
-        $mapped = $ok->map(fn($it) => strrev($it));
-        $this->assertTrue($mapped->isOK(), 'The mapped result should be "OK"');
-        $this->assertEquals('dray', $mapped->getOK(), 'The mapping function was not called correctly');
-    }
-
-    #[TestDox('Map fails for OK result when mapping is null')]
-    public function testMapFailsForOKResultWhenMappingIsNull(): void
-    {
-        $this->expectException(InvalidArgumentException::class);
-        Result::OK('not null')->map(fn($it) => null);
-    }
-
-    #[TestDox('Map succeeds for Error result')]
-    public function testMapSucceedsForErrorResult(): void
-    {
-        $tattle = new class { public bool $called = false; };
-        $error  = Result::Error('nope');
-        $mapped = $error->map(function () use ($tattle)
-        {
-            $tattle->called = true;
-            return 'hello';
-        });
-        $this->assertTrue($mapped->isError(), 'The mapped result should be "Error"');
-        $this->assertFalse($tattle->called, 'The mapping function should not have been called');
-        $this->assertSame($error, $mapped, 'The same "Error" instance should have been returned');
-    }
-
-    #[TestDox('MapError succeeds for OK result')]
-    public function testMapErrorSucceedsForOKResult(): void
-    {
-        $tattle = new class { public bool $called = false; };
-        $ok     = Result::OK('sure');
-        $mapped = $ok->mapError(function () use ($tattle)
-        {
-            $tattle->called = true;
-            return 'hello';
-        });
-        $this->assertTrue($mapped->isOK(), 'The mapped result should be "OK"');
-        $this->assertFalse($tattle->called, 'The mapping function should not have been called');
-        $this->assertSame($ok, $mapped, 'The same "OK" instance should have been returned');
-    }
-
-    #[TestDox('MapError succeeds for Error result')]
-    public function testMapErrorSucceedsForErrorResult(): void
-    {
-        $error  = Result::Error('taco');
-        $mapped = $error->mapError(fn($it) => str_repeat('*', strlen($it)));
-        $this->assertTrue($mapped->isError(), 'The mapped result should be "Error"');
-        $this->assertEquals('****', $mapped->getError(), 'The mapping function was not called correctly');
-    }
-
-    #[TestDox('MapError fails for Error result when mapping is null')]
-    public function testMapErrorFailsForErrorResultWhenMappingIsNull(): void
-    {
-        $this->expectException(InvalidArgumentException::class);
-        Result::Error('pizza')->mapError(fn($it) => null);
-    }
-
-    #[TestDox('Iter succeeds for OK result')]
-    public function testIterSucceedsForOKResult(): void
-    {
-        $target = new class { public mixed $called = null; };
-        Result::OK(77)->iter(function ($it) use ($target) { $target->called = $it; });
-        $this->assertEquals(77, $target->called, 'The function should have been called with the "OK" value');
-    }
-
-    #[TestDox('Iter succeeds for Error result')]
-    public function testIterSucceedsForErrorResult(): void
-    {
-        $target = new class { public mixed $called = null; };
-        Result::Error('')->iter(function () use ($target) { $target->called = 'uh oh'; });
-        $this->assertNull($target->called, 'The function should not have been called');
-    }
-
-    #[TestDox('ToOption succeeds for OK result')]
-    public function testToOptionSucceedsForOKResult()
-    {
-        $value = Result::OK(99)->toOption();
-        $this->assertTrue($value->isSome(), 'An "OK" result should map to a "Some" option');
-        $this->assertEquals(99, $value->get(), 'The value is not correct');
-    }
-
-    #[TestDox('ToOption succeeds for Error result')]
-    public function testToOptionSucceedsForErrorResult()
-    {
-        $value = Result::Error('file not found')->toOption();
-        $this->assertTrue($value->isNone(), 'An "Error" result should map to a "None" option');
-    }
-
-    #[TestDox('Tap succeeds for OK result')]
-    public function testTapSucceedsForOKResult(): void
-    {
-        $value    = '';
-        $original = Result::OK('working');
-        $tapped   = $original->tap(function (Result $it) use (&$value) {
-            $value = $it->isOK() ? 'OK: ' . $it->getOK() : 'Error: ' . $it->getError();
-        });
-        $this->assertEquals('OK: working', $value, 'The tapped function was not called');
-        $this->assertSame($original, $tapped, 'The same result should have been returned');
-    }
-
-    #[TestDox('Tap succeeds for Error result')]
-    public function testTapSucceedsForErrorResult(): void
-    {
-        $value    = '';
-        $original = Result::Error('failed');
-        $tapped   = $original->tap(function (Result $it) use (&$value) {
-            $value = $it->isOK() ? 'OK: ' . $it->getOK() : 'Error: ' . $it->getError();
-        });
-        $this->assertEquals('Error: failed', $value, 'The tapped function was not called');
-        $this->assertSame($original, $tapped, 'The same result should have been returned');
-    }
-
-    #[TestDox('OK succeeds for non null result')]
-    public function testOKSucceedsForNonNullResult(): void
-    {
-        $result = Result::OK('something');
-        $this->assertTrue($result->isOK(), 'The result should have been "OK"');
-        $this->assertEquals('something', $result->getOK(), 'The "OK" value was incorrect');
-    }
-
-    #[TestDox('OK fails for null result')]
-    public function testOKFailsForNullResult(): void
-    {
-        $this->expectException(InvalidArgumentException::class);
-        Result::OK(null);
-    }
-
-    #[TestDox('Error succeeds for non null result')]
-    public function testErrorSucceedsForNonNullResult(): void
-    {
-        $result = Result::Error('sad trombone');
-        $this->assertTrue($result->isError(), 'The result should have been "Error"');
-        $this->assertEquals('sad trombone', $result->getError(), 'The "Error" value was incorrect');
-    }
-
-    #[TestDox('Error fails for null result')]
-    public function testErrorFailsForNullResult(): void
-    {
-        $this->expectException(InvalidArgumentException::class);
-        Result::Error(null);
-    }
-}

tests/Unit/OptionTest.php

@@ -0,0 +1,256 @@
+<?php
+/**
+ * @author Daniel J. Summers <daniel@bitbadger.solutions>
+ * @license MIT
+ */
+
+declare(strict_types=1);
+
+use BitBadger\InspiredByFSharp\Option;
+use PhpOption\{None, Some};
+
+describe('->get()', function () {
+    test('retrieves the value for Some', function () {
+        expect(Option::Some(9)->get())->toBe(9);
+    });
+    test('throws an exception for None', function () {
+        expect(fn() => Option::None()->get())->toThrow(InvalidArgumentException::class);
+    });
+});
+
+describe('->isNone()', function () {
+    test('returns true for None', function () {
+        expect(Option::None()->isNone())->toBeTrue();
+    });
+    test('returns false for Some', function () {
+        expect(Option::Some(8)->isNone())->toBeFalse();
+    });
+});
+
+describe('->isSome()', function () {
+    test('returns false for None', function () {
+        expect(Option::None()->isSome())->toBeFalse();
+    });
+    test('returns true for Some', function () {
+        expect(Option::Some('boo')->isSome())->toBeTrue();
+    });
+});
+
+describe('->getOrDefault()', function () {
+    test('returns default value for None', function () {
+        expect(Option::None()->getOrDefault('yes'))->toBe('yes');
+    });
+    test('returns option value for Some', function () {
+        expect(Option::Some('no')->getOrDefault('yes'))->toBe('no');
+    });
+});
+
+describe('->getOrCall()', function () {
+    test('returns value from callable for None', function () {
+        expect(Option::None()->getOrCall(fn() => 'called'))->toBe('called');
+    });
+    test('returns option value for Some', function () {
+        expect(Option::Some('passed')->getOrCall(fn() => 'called'))->toBe('passed');
+    });
+});
+
+describe('->getOrThrow()', function () {
+    test('throws an exception for None', function () {
+        expect(fn() => Option::None()->getOrThrow(fn() => throw new BadMethodCallException()))
+            ->toThrow(BadMethodCallException::class);
+    });
+    test('returns option value for Some', function () {
+        expect(Option::Some('no throw')->getOrThrow(fn() => throw new BadMethodCallException()))->toBe('no throw');
+    });
+});
+
+describe('->bind()', function () {
+    test('returns None when binding against None', function () {
+        $original = Option::None();
+        $bound = $original->bind(fn($it) => Option::Some('value'));
+        expect($bound)->isNone()->toBeTrue()->and($bound)->toBe($original);
+    });
+    test('returns Some when binding against Some with Some', function () {
+        expect(Option::Some('hello')->bind(fn($it) => Option::Some('goodbye')))
+            ->isSome()->toBeTrue()->get()->toBe('goodbye');
+    });
+    test('returns None when binding against Some with None', function () {
+        expect(Option::Some('greetings')->bind(fn($it) => Option::None()))->isNone()->toBeTrue();
+    });
+});
+
+describe('->contains()', function () {
+    test('returns false for None', function () {
+        expect(Option::None()->contains(null))->toBeFalse();
+    });
+    test('returns true for Some when strict equality is matched', function () {
+        expect(Option::Some(3)->contains(3))->toBeTrue();
+    });
+    test('returns false for Some when strict equality is not matched', function () {
+        expect(Option::Some('3')->contains(3))->toBeFalse();
+    });
+    test('returns true for Some when loose equality is matched', function () {
+        expect(Option::Some('3')->contains(3, strict: false))->toBeTrue();
+    });
+    test('returns false for Some when loose equality is not matched', function () {
+        expect(Option::Some('3')->contains(4, strict: false))->toBeFalse();
+    });
+});
+
+describe('->exists()', function () {
+    test('returns false for None', function () {
+        expect(Option::None()->exists(fn($it) => true))->toBeFalse();
+    });
+    test('returns true for Some and matching condition', function () {
+        expect(Option::Some(14)->exists(fn($it) => $it < 100))->toBeTrue();
+    });
+    test('returns false for Some and non-matching condition', function () {
+        expect(Option::Some(14)->exists(fn($it) => $it > 100))->toBeFalse();
+    });
+});
+
+describe('->map()', function () {
+    test('does nothing for None', function () {
+        $tattle = new class { public bool $called = false; };
+        $none   = Option::None();
+        $mapped = $none->map(function () use ($tattle)
+        {
+            $tattle->called = true;
+            return 'hello';
+        });
+        expect($mapped)
+            ->isNone()->toBeTrue()
+            ->and($tattle->called)->toBeFalse()
+            ->and($mapped)->toBe($none);
+    });
+    test('maps value for Some', function () {
+        expect(Option::Some('abc ')->map(fn($it) => str_repeat($it, 2)))
+            ->isSome()->toBeTrue()->get()->toBe('abc abc ');
+    });
+    test('throws an exception if mapping returns null', function () {
+        expect(fn() => Option::Some('oof')->map(fn($it) => null))->toThrow(InvalidArgumentException::class);
+    });
+});
+
+describe('->iter()', function () {
+    test('does nothing for None', function () {
+        $target = new class { public mixed $called = null; };
+        Option::None()->iter(function () use ($target) { $target->called = 'uh oh'; });
+        expect($target->called)->toBeNull();
+    });
+    test('iterates for Some', function () {
+        $target = new class { public mixed $called = null; };
+        Option::Some(33)->iter(function ($it) use ($target) { $target->called = $it; });
+        expect($target->called)->toBe(33);
+    });
+});
+
+describe('->filter()', function () {
+    test('does nothing for None', function () {
+        $tattle   = new class { public bool $called = false; };
+        $none     = Option::None();
+        $filtered = $none->filter(function () use ($tattle)
+        {
+            $tattle->called = true;
+            return true;
+        });
+        expect($filtered)
+            ->isNone()->toBeTrue()
+            ->and($tattle->called)->toBeFalse()
+            ->and($filtered)->toBe($none);
+    });
+    test('returns Some when filter is matched', function () {
+        $some     = Option::Some(12);
+        $filtered = $some->filter(fn($it) => $it % 2 === 0);
+        expect($filtered)
+            ->isSome()->toBeTrue()
+            ->get()->toBe(12)
+            ->and($filtered)->toBe($some);
+    });
+    test('returns None when filter is not matched', function () {
+        expect(Option::Some(23)->filter(fn($it) => $it % 2 === 0)->isNone())->toBeTrue();
+    });
+});
+
+describe('->unwrap()', function () {
+    test('returns null for None', function () {
+        expect(Option::None()->unwrap())->toBeNull();
+    });
+    test('returns option value for Some', function () {
+        expect(Option::Some('boy howdy')->unwrap())->toBe('boy howdy');
+    });
+});
+
+describe('->tap()', function () {
+    test('is called for None', function () {
+        $value    = '';
+        $original = Option::None();
+        $tapped   = $original->tap(
+            function (Option $it) use (&$value) { $value = $it->isSome() ? $it->get() : 'none'; });
+        expect($value)->toBe('none')->and($original)->toBe($tapped);
+    });
+    test('is called for Some', function () {
+        $value    = '';
+        $original = Option::Some('testing');
+        $tapped   = $original->tap(
+            function (Option $it) use (&$value) { $value = $it->isSome() ? $it->get() : 'none'; });
+        expect($value)->toBe('testing')->and($original)->toBe($tapped);
+    });
+});
+
+describe('->toArray()', function () {
+    test('returns empty array for None', function () {
+        expect(Option::None()->toArray())->not->toBeNull()->toBeEmpty();
+    });
+    test('returns one-item array for Some', function () {
+        expect(Option::Some('15')->toArray())->not->toBeNull()->toBe(['15']);
+    });
+});
+
+describe('->toPhpOption()', function () {
+    test('converts None', function () {
+        expect(Option::None()->toPhpOption())
+            ->toBeInstanceOf('PhpOption\None')
+            ->not->toBeNull()
+            ->isDefined()->toBeFalse();
+    });
+    test('converts Some', function () {
+        expect(Option::Some('php')->toPhpOption())
+            ->toBeInstanceOf('PhpOption\Some')
+            ->not->toBeNull()
+            ->isDefined()->toBeTrue()
+            ->get()->toBe('php');
+    });
+});
+
+describe('::Some()', function () {
+    test('creates a Some option when given a value', function () {
+        expect(Option::Some('hello'))->not->toBeNull()->isSome()->toBeTrue();
+    });
+    test('throws an exception when given null', function () {
+        expect(fn() => Option::Some(null))->toThrow(InvalidArgumentException::class);
+    });
+});
+
+describe('::None()', function () {
+    test('creates a None option', function () {
+        expect(Option::None())->not->toBeNull()->isNone()->toBeTrue();
+    });
+});
+
+describe('::of()', function () {
+    test('creates a None option when given null', function () {
+        expect(Option::of(null))->not->toBeNull()->isNone()->toBeTrue();
+    });
+    test('creates a Some option when given a value', function () {
+        expect(Option::of('test'))->not->toBeNull()
+            ->isSome()->toBeTrue()
+            ->get()->toBe('test');
+    });
+    test('creates a None option when given PhpOption\None', function () {
+        expect(Option::of(None::create()))->isNone()->toBeTrue();
+    });
+    test('creates a Some option when given PhpOption\Some', function () {
+        expect(Option::of(Some::create('something')))->isSome()->toBeTrue()->get()->toBe('something');
+    });
+});

tests/Unit/ResultTest.php

@@ -0,0 +1,206 @@
+<?php
+/**
+ * @author Daniel J. Summers <daniel@bitbadger.solutions>
+ * @license MIT
+ */
+
+declare(strict_types=1);
+
+use BitBadger\InspiredByFSharp\{Option, Result};
+
+describe('->getOK()', function () {
+    test('returns OK value for OK result', function () {
+        expect(Result::OK('yay')->getOK())->toBe('yay');
+    });
+    test('throws an exception for Error result', function () {
+        expect(fn() => Result::Error('whoops')->getOK())->toThrow(InvalidArgumentException::class);
+    });
+});
+
+describe('->getError()', function () {
+    test('throws an exception for OK result', function () {
+        expect(fn() => Result::OK('yeah')->getError())->toThrow(InvalidArgumentException::class);
+    });
+    test('returns Error value for Error result', function () {
+        expect(Result::Error('boo')->getError())->toBe('boo');
+    });
+});
+
+describe('->isOK()', function () {
+    test('returns true for OK result', function () {
+        expect(Result::OK('ok')->isOK())->toBeTrue();
+    });
+    test('returns false for Error result', function () {
+        expect(Result::Error('error')->isOK())->toBeFalse();
+    });
+});
+
+describe('->isError()', function () {
+    test('returns false for OK result', function () {
+        expect(Result::OK('fine')->isError())->toBeFalse();
+    });
+    test('returns true for Error result', function () {
+        expect(Result::Error('not ok')->isError())->toBeTrue();
+    });
+});
+
+describe('->bind()', function () {
+    test('returns OK when binding against OK with OK', function () {
+        expect(Result::OK('one')->bind(fn($it) => Result::OK("$it two")))
+            ->isOK()->toBeTrue()->getOK()->toBe('one two');
+    });
+    test('returns Error when binding against OK with Error', function () {
+        expect(Result::OK('three')->bind(fn($it) => Result::Error('back to two')))
+            ->isError()->toBeTrue()->getError()->toBe('back to two');
+    });
+    test('returns Error when binding against Error', function () {
+        $original = Result::Error('oops');
+        $result   = $original->bind(fn($it) => Result::OK('never mind - it worked!'));
+        expect($result->isError())->toBeTrue()
+            ->and($result)->toBe($original);
+    });
+});
+
+describe('->contains()', function () {
+    test('returns true when OK is strictly equal', function () {
+        expect(Result::OK(18)->contains(18))->toBeTrue();
+    });
+    test('returns false when OK is not strictly equal', function () {
+        expect(Result::OK(18)->contains('18'))->toBeFalse();
+    });
+    test('returns true when OK is loosely equal', function () {
+        expect(Result::OK(18)->contains('18', strict: false))->toBeTrue();
+    });
+    test('returns false when OK is not loosely equal', function () {
+        expect(Result::OK(18)->contains(17, strict: false))->toBeFalse();
+    });
+    test('returns false for Error', function () {
+        expect(Result::Error('ouch')->contains('ouch'))->toBeFalse();
+    });
+});
+
+describe('->exists()', function () {
+    test('returns true for OK when condition matches', function () {
+        expect(Result::OK(14)->exists(fn($it) => $it < 100))->toBeTrue();
+    });
+    test('returns false for OK when condition does not match', function () {
+        expect(Result::OK(14)->exists(fn($it) => $it > 100))->toBeFalse();
+    });
+    test('returns false for Error', function () {
+        expect(Result::Error(true)->exists(fn($it) => true))->toBeFalse();
+    });
+});
+
+describe('->map()', function () {
+    test('maps value for OK', function () {
+        expect(Result::OK('yard')->map(fn($it) => strrev($it)))
+            ->isOK()->toBeTrue()->getOK()->toBe('dray');
+    });
+    test('throws an exception for OK when mapping result is null', function () {
+        expect(fn() => Result::OK('not null')->map(fn($it) => null))->toThrow(InvalidArgumentException::class);
+    });
+    test('does nothing for Error', function () {
+        $tattle = new class { public bool $called = false; };
+        $error  = Result::Error('nope');
+        $mapped = $error->map(function () use ($tattle)
+        {
+            $tattle->called = true;
+            return 'hello';
+        });
+        expect($mapped)
+            ->isError()->toBeTrue()
+            ->and($tattle->called)->toBeFalse()
+            ->and($mapped)->toBe($error);
+    });
+});
+
+describe('->mapError()', function () {
+    test('does nothing for OK', function () {
+        $tattle = new class { public bool $called = false; };
+        $ok     = Result::OK('sure');
+        $mapped = $ok->mapError(function () use ($tattle)
+        {
+            $tattle->called = true;
+            return 'hello';
+        });
+        expect($mapped)
+            ->isOK()->toBeTrue()
+            ->and($tattle->called)->toBeFalse()
+            ->and($mapped)->toBe($ok);
+    });
+    test('maps value for Error', function () {
+        expect(Result::Error('taco')->mapError(fn($it) => str_repeat('*', strlen($it))))
+            ->isError()->toBeTrue()->getError()->toBe('****');
+    });
+    test('throws an exception for Error when mapping result is null', function () {
+        expect(fn() => Result::Error('pizza')->mapError(fn($it) => null))->toThrow(InvalidArgumentException::class);
+    });
+});
+
+describe('->iter()', function () {
+    test('iterates for OK', function () {
+        $target = new class { public mixed $called = null; };
+        Result::OK(77)->iter(function ($it) use ($target) { $target->called = $it; });
+        expect($target->called)->toBe(77);
+    });
+    test('does nothing for Error', function () {
+        $target = new class { public mixed $called = null; };
+        Result::Error('')->iter(function () use ($target) { $target->called = 'uh oh'; });
+        expect($target->called)->toBeNull();
+    });
+});
+
+describe('->toArray()', function () {
+    test('returns a one-item array for OK', function () {
+        expect(Result::OK('yay')->toArray())->not->toBeNull()->toBe(['yay']);
+    });
+    test('returns an empty array for Error', function () {
+        expect(Result::Error('oh no')->toArray())->not->toBeNull()->toBeEmpty();
+    });
+});
+
+describe('->toOption()', function () {
+    test('returns a Some option for OK', function () {
+        expect(Result::OK(99)->toOption())->isSome()->toBeTrue()->get()->toBe(99);
+    });
+    test('returns a None option for Error', function () {
+        expect(Result::Error('file not found')->toOption())->isNone()->toBeTrue();
+    });
+});
+
+describe('->tap()', function () {
+    test('is called for OK', function () {
+        $value = '';
+        $original = Result::OK('working');
+        $tapped = $original->tap(function (Result $it) use (&$value) {
+            $value = $it->isOK() ? 'OK: ' . $it->getOK() : 'Error: ' . $it->getError();
+        });
+        expect($value)->toBe('OK: working')->and($tapped)->toBe($original);
+    });
+    test('is called for Error', function () {
+        $value    = '';
+        $original = Result::Error('failed');
+        $tapped   = $original->tap(function (Result $it) use (&$value) {
+            $value = $it->isOK() ? 'OK: ' . $it->getOK() : 'Error: ' . $it->getError();
+        });
+        expect($value)->toBe('Error: failed')->and($tapped)->toBe($original);
+    });
+});
+
+describe('::OK()', function () {
+    test('creates an OK result for a non-null value', function () {
+        expect(Result::OK('something'))->isOK()->toBeTrue()->getOK()->toBe('something');
+    });
+    test('throws an exception for OK with a null value', function () {
+        expect(fn() => Result::OK(null))->toThrow(InvalidArgumentException::class);
+    });
+});
+
+describe('::Error()', function () {
+    test('creates an Error result for a non-null value', function () {
+        expect(Result::Error('sad trombone'))->isError()->toBeTrue()->getError()->toBe('sad trombone');
+    });
+    test('throws an exception for Error with a null value', function () {
+        expect(fn() => Result::Error(null))->toThrow(InvalidArgumentException::class);
+    });
+});