From 5527322678ccb606150b2c44a1f5add166d60a12 Mon Sep 17 00:00:00 2001
From: Sergei Predvoditelev <sergei@predvoditelev.ru>
Date: Tue, 3 Feb 2026 11:09:49 +0300
Subject: [PATCH 1/9] Add `StreamMock`

---
 CHANGELOG.md                         |   2 +-
 composer.json                        |   1 +
 docs/guide/en/README.md              |  66 ++++
 src/HttpMessage/StreamMock.php       | 204 +++++++++++
 tests/HttpMessage/StreamMockTest.php | 500 +++++++++++++++++++++++++++
 5 files changed, 772 insertions(+), 1 deletion(-)
 create mode 100644 src/HttpMessage/StreamMock.php
 create mode 100644 tests/HttpMessage/StreamMockTest.php

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 766451f..b7c4385 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,7 +2,7 @@
 
 ## 3.1.1 under development
 
-- no changes in this release.
+- New #85: Add `StreamMock` (@vjik)
 
 ## 3.1.0 December 01, 2025
 
diff --git a/composer.json b/composer.json
index ab35dd3..ae92c58 100644
--- a/composer.json
+++ b/composer.json
@@ -31,6 +31,7 @@
         "psr/clock": "^1.0",
         "psr/container": "^1.0 || ^2.0",
         "psr/event-dispatcher": "^1.0",
+        "psr/http-message": "^1.1 || ^2.0",
         "psr/log": "^2.0|^3.0",
         "psr/simple-cache": "^2.0|^3.0"
     },
diff --git a/docs/guide/en/README.md b/docs/guide/en/README.md
index c56f2ef..a7a7ea2 100644
--- a/docs/guide/en/README.md
+++ b/docs/guide/en/README.md
@@ -129,3 +129,69 @@ sleep(10);
 
 echo $clock->now(); // Same value as above.
 ```
+
+## Stream mock [PSR-7](https://www.php-fig.org/psr/psr-7/) 
+
+The `StreamMock` class is a test-specific implementation of `StreamInterface`.
+It allows you to create stream instances with configurable behavior for testing HTTP message handling.
+
+```php
+use Yiisoft\Test\Support\HttpMessage\StreamMock;
+
+// Create a stream with content
+$stream = new StreamMock('Hello, World!');
+
+echo $stream; // Hello, World!
+echo $stream->getSize(); // 13
+echo $stream->read(5); // Hello
+echo $stream->getContents(); // , World!
+```
+
+You can configure stream behavior through constructor parameters:
+
+```php
+// Create a read-only stream
+$readOnlyStream = new StreamMock('content', writable: false);
+
+// Create a non-seekable stream
+$nonSeekableStream = new StreamMock('content', seekable: false);
+
+// Create a stream with custom initial position
+$stream = new StreamMock('Hello', position: 3);
+echo $stream->getContents(); // lo
+```
+
+Custom metadata can be provided as an array or a closure:
+
+```php
+// Array metadata
+$stream = new StreamMock(
+    'content',
+    metadata: [
+        'uri' => 'php://memory',
+        'mode' => 'r+',
+    ],
+);
+
+// Closure metadata (receives the stream instance)
+$stream = new StreamMock(
+    'content', 
+    metadata: static fn(StreamMock $s) => [
+        'size' => $s->getSize(),
+        'eof' => $s->eof(),
+    ],
+);
+```
+
+The stream provides helper methods to check its state:
+
+```php
+$stream = new StreamMock('content');
+
+$stream->isClosed(); // false
+$stream->isDetached(); // false
+$stream->getPosition(); // 0
+
+$stream->close();
+$stream->isClosed(); // true
+```
diff --git a/src/HttpMessage/StreamMock.php b/src/HttpMessage/StreamMock.php
new file mode 100644
index 0000000..f5dfd08
--- /dev/null
+++ b/src/HttpMessage/StreamMock.php
@@ -0,0 +1,204 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Yiisoft\Test\Support\HttpMessage;
+
+use Closure;
+use Psr\Http\Message\StreamInterface;
+use RuntimeException;
+
+use function is_array;
+use function strlen;
+
+/**
+ * @psalm-type MetadataClosure = Closure(StreamMock): array<string, mixed>
+ */
+final class StreamMock implements StreamInterface
+{
+    private bool $closed = false;
+    private bool $detached = false;
+
+    /**
+     * @psalm-param MetadataClosure|array|null $metadata
+     */
+    public function __construct(
+        private string $content = '',
+        private int $position = 0,
+        private bool $readable = true,
+        private bool $writable = true,
+        private bool $seekable = true,
+        private Closure|array|null $metadata = null,
+    ) {
+    }
+
+    public function __toString(): string
+    {
+        return $this->content;
+    }
+
+    public function isClosed(): bool
+    {
+        return $this->closed;
+    }
+
+    public function isDetached(): bool
+    {
+        return $this->detached;
+    }
+
+    public function getPosition(): int
+    {
+        return $this->position;
+    }
+
+    public function close(): void
+    {
+        $this->closed = true;
+    }
+
+    public function detach()
+    {
+        $this->detached = true;
+        $this->close();
+        return null;
+    }
+
+    public function getSize(): ?int
+    {
+        return $this->getContentSize();
+    }
+
+    public function tell(): int
+    {
+        if ($this->closed) {
+            throw new RuntimeException('Stream is closed.');
+        }
+
+        return $this->position;
+    }
+
+    public function eof(): bool
+    {
+        return $this->closed || $this->position >= $this->getContentSize();
+    }
+
+    public function isSeekable(): bool
+    {
+        return $this->seekable && !$this->closed;
+    }
+
+    public function seek(int $offset, int $whence = SEEK_SET): void
+    {
+        if (!$this->seekable) {
+            throw new RuntimeException('Stream is not seekable.');
+        }
+
+        if ($this->closed) {
+            throw new RuntimeException('Stream is closed.');
+        }
+
+        $size = $this->getContentSize();
+
+        $newPosition = match ($whence) {
+            SEEK_SET => $offset,
+            SEEK_CUR => $this->position + $offset,
+            SEEK_END => $size + $offset,
+            default => throw new RuntimeException('Invalid whence value.'),
+        };
+
+        if ($newPosition < 0 || $newPosition > $size) {
+            throw new RuntimeException('Invalid seek position.');
+        }
+
+        $this->position = $newPosition;
+    }
+
+    public function rewind(): void
+    {
+        $this->seek(0);
+    }
+
+    public function isWritable(): bool
+    {
+        return $this->writable && !$this->closed;
+    }
+
+    public function write(string $string): int
+    {
+        if (!$this->writable) {
+            throw new RuntimeException('Stream is not writable.');
+        }
+
+        if ($this->closed) {
+            throw new RuntimeException('Stream is closed.');
+        }
+
+        $size = strlen($string);
+        $this->content = substr($this->content, 0, $this->position)
+            . $string
+            . substr($this->content, $this->position + $size);
+        $this->position += $size;
+
+        return $size;
+    }
+
+    public function isReadable(): bool
+    {
+        return $this->readable && !$this->closed;
+    }
+
+    public function read(int $length): string
+    {
+        if (!$this->readable) {
+            throw new RuntimeException('Stream is not readable.');
+        }
+
+        if ($this->closed) {
+            throw new RuntimeException('Stream is closed.');
+        }
+
+        if ($this->position >= $this->getContentSize()) {
+            return '';
+        }
+
+        $result = substr($this->content, $this->position, $length);
+        $this->position += strlen($result);
+
+        return $result;
+    }
+
+    public function getContents(): string
+    {
+        return $this->read(
+            $this->getContentSize() - $this->position,
+        );
+    }
+
+    public function getMetadata(?string $key = null)
+    {
+        if ($this->closed) {
+            return $key === null ? [] : null;
+        }
+
+        $metadata = match (true) {
+            is_array($this->metadata) => $this->metadata,
+            $this->metadata instanceof Closure => ($this->metadata)($this),
+            default => [
+                'eof' => $this->eof(),
+                'seekable' => $this->isSeekable(),
+            ],
+        };
+
+        if ($key === null) {
+            return $metadata;
+        }
+
+        return $metadata[$key] ?? null;
+    }
+
+    private function getContentSize(): int
+    {
+        return strlen($this->content);
+    }
+}
diff --git a/tests/HttpMessage/StreamMockTest.php b/tests/HttpMessage/StreamMockTest.php
new file mode 100644
index 0000000..67c2a41
--- /dev/null
+++ b/tests/HttpMessage/StreamMockTest.php
@@ -0,0 +1,500 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Yiisoft\Test\Support\Tests\HttpMessage;
+
+use PHPUnit\Framework\TestCase;
+use RuntimeException;
+use Yiisoft\Test\Support\HttpMessage\StreamMock;
+
+final class StreamMockTest extends TestCase
+{
+    public function testBase(): void
+    {
+        $stream = new StreamMock();
+
+        $this->assertSame(0, $stream->getSize());
+        $this->assertSame(0, $stream->getPosition());
+        $this->assertSame('', (string) $stream);
+        $this->assertSame('', $stream->getContents());
+        $this->assertTrue($stream->isReadable());
+        $this->assertTrue($stream->isWritable());
+        $this->assertTrue($stream->isSeekable());
+        $this->assertFalse($stream->isClosed());
+        $this->assertFalse($stream->isDetached());
+    }
+
+    public function testConstructorWithContent(): void
+    {
+        $stream = new StreamMock('Hello, World!');
+
+        $this->assertSame('Hello, World!', (string) $stream);
+        $this->assertSame(13, $stream->getSize());
+    }
+
+    public function testConstructorWithPosition(): void
+    {
+        $stream = new StreamMock('Hello', position: 3);
+
+        $this->assertSame(3, $stream->getPosition());
+        $this->assertSame('lo', $stream->getContents());
+    }
+
+    public function testConstructorWithReadableFlag(): void
+    {
+        $stream = new StreamMock(readable: false);
+
+        $this->assertFalse($stream->isReadable());
+    }
+
+    public function testConstructorWithWritableFlag(): void
+    {
+        $stream = new StreamMock(writable: false);
+
+        $this->assertFalse($stream->isWritable());
+    }
+
+    public function testConstructorWithSeekableFlag(): void
+    {
+        $stream = new StreamMock(seekable: false);
+
+        $this->assertFalse($stream->isSeekable());
+    }
+
+    public function testToString(): void
+    {
+        $stream = new StreamMock('Test content');
+
+        $this->assertSame('Test content', (string) $stream);
+    }
+
+    public function testClose(): void
+    {
+        $stream = new StreamMock('content');
+
+        $this->assertFalse($stream->isClosed());
+
+        $stream->close();
+
+        $this->assertTrue($stream->isClosed());
+        $this->assertFalse($stream->isReadable());
+        $this->assertFalse($stream->isWritable());
+        $this->assertFalse($stream->isSeekable());
+    }
+
+    public function testDetach(): void
+    {
+        $stream = new StreamMock('content');
+
+        $this->assertFalse($stream->isDetached());
+
+        $result = $stream->detach();
+
+        $this->assertNull($result);
+        $this->assertTrue($stream->isDetached());
+        $this->assertTrue($stream->isClosed());
+    }
+
+    public function testGetSize(): void
+    {
+        $stream = new StreamMock('');
+        $this->assertSame(0, $stream->getSize());
+
+        $stream = new StreamMock('Hello');
+        $this->assertSame(5, $stream->getSize());
+
+        $stream = new StreamMock('Привет');
+        $this->assertSame(12, $stream->getSize()); // UTF-8 bytes
+    }
+
+    public function testTell(): void
+    {
+        $stream = new StreamMock('Hello', position: 0);
+        $this->assertSame(0, $stream->tell());
+
+        $stream = new StreamMock('Hello', position: 3);
+        $this->assertSame(3, $stream->tell());
+    }
+
+    public function testTellThrowsExceptionWhenClosed(): void
+    {
+        $stream = new StreamMock('Hello');
+        $stream->close();
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Stream is closed.');
+        $stream->tell();
+    }
+
+    public function testEof(): void
+    {
+        $stream = new StreamMock('Hello', position: 0);
+        $this->assertFalse($stream->eof());
+
+        $stream = new StreamMock('Hello', position: 5);
+        $this->assertTrue($stream->eof());
+
+        $stream = new StreamMock('Hello', position: 10);
+        $this->assertTrue($stream->eof());
+    }
+
+    public function testEofWhenClosed(): void
+    {
+        $stream = new StreamMock('Hello');
+        $stream->close();
+
+        $this->assertTrue($stream->eof());
+    }
+
+    public function testSeekSet(): void
+    {
+        $stream = new StreamMock('Hello World');
+
+        $stream->seek(5);
+        $this->assertSame(5, $stream->getPosition());
+
+        $stream->seek(0);
+        $this->assertSame(0, $stream->getPosition());
+    }
+
+    public function testSeekCur(): void
+    {
+        $stream = new StreamMock('Hello World', position: 3);
+
+        $stream->seek(2, SEEK_CUR);
+        $this->assertSame(5, $stream->getPosition());
+
+        $stream->seek(-3, SEEK_CUR);
+        $this->assertSame(2, $stream->getPosition());
+    }
+
+    public function testSeekEnd(): void
+    {
+        $stream = new StreamMock('Hello World');
+
+        $stream->seek(0, SEEK_END);
+        $this->assertSame(11, $stream->getPosition());
+
+        $stream->seek(-5, SEEK_END);
+        $this->assertSame(6, $stream->getPosition());
+    }
+
+    public function testSeekThrowsExceptionWhenNotSeekable(): void
+    {
+        $stream = new StreamMock('Hello', seekable: false);
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Stream is not seekable.');
+        $stream->seek(0);
+    }
+
+    public function testSeekThrowsExceptionWhenClosed(): void
+    {
+        $stream = new StreamMock('Hello');
+        $stream->close();
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Stream is closed.');
+        $stream->seek(0);
+    }
+
+    public function testSeekThrowsExceptionForInvalidWhence(): void
+    {
+        $stream = new StreamMock('Hello');
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Invalid whence value.');
+        $stream->seek(0, 999);
+    }
+
+    public function testSeekThrowsExceptionForNegativePosition(): void
+    {
+        $stream = new StreamMock('Hello');
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Invalid seek position.');
+        $stream->seek(-1);
+    }
+
+    public function testSeekThrowsExceptionForPositionBeyondSize(): void
+    {
+        $stream = new StreamMock('Hello');
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Invalid seek position.');
+        $stream->seek(100);
+    }
+
+    public function testRewind(): void
+    {
+        $stream = new StreamMock('Hello', position: 5);
+
+        $stream->rewind();
+
+        $this->assertSame(0, $stream->getPosition());
+    }
+
+    public function testWrite(): void
+    {
+        $stream = new StreamMock();
+
+        $bytesWritten = $stream->write('Hello');
+
+        $this->assertSame(5, $bytesWritten);
+        $this->assertSame('Hello', (string) $stream);
+        $this->assertSame(5, $stream->getPosition());
+    }
+
+    public function testWriteAtPosition(): void
+    {
+        $stream = new StreamMock('Hello World', position: 6);
+
+        $stream->write('PHP');
+
+        $this->assertSame('Hello PHPld', (string) $stream);
+        $this->assertSame(9, $stream->getPosition());
+    }
+
+    public function testWriteOverwrite(): void
+    {
+        $stream = new StreamMock('AAAAA', position: 0);
+
+        $stream->write('BB');
+
+        $this->assertSame('BBAAA', (string) $stream);
+    }
+
+    public function testWriteThrowsExceptionWhenNotWritable(): void
+    {
+        $stream = new StreamMock(writable: false);
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Stream is not writable.');
+        $stream->write('test');
+    }
+
+    public function testWriteThrowsExceptionWhenClosed(): void
+    {
+        $stream = new StreamMock();
+        $stream->close();
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Stream is closed.');
+        $stream->write('test');
+    }
+
+    public function testRead(): void
+    {
+        $stream = new StreamMock('Hello World');
+
+        $result = $stream->read(5);
+
+        $this->assertSame('Hello', $result);
+        $this->assertSame(5, $stream->getPosition());
+    }
+
+    public function testReadFromPosition(): void
+    {
+        $stream = new StreamMock('Hello World', position: 6);
+
+        $result = $stream->read(5);
+
+        $this->assertSame('World', $result);
+    }
+
+    public function testReadBeyondContent(): void
+    {
+        $stream = new StreamMock('Hi');
+
+        $result = $stream->read(100);
+
+        $this->assertSame('Hi', $result);
+        $this->assertSame(2, $stream->getPosition());
+    }
+
+    public function testReadAtEof(): void
+    {
+        $stream = new StreamMock('Hello', position: 5);
+
+        $result = $stream->read(10);
+
+        $this->assertSame('', $result);
+    }
+
+    public function testReadThrowsExceptionWhenNotReadable(): void
+    {
+        $stream = new StreamMock('content', readable: false);
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Stream is not readable.');
+        $stream->read(5);
+    }
+
+    public function testReadThrowsExceptionWhenClosed(): void
+    {
+        $stream = new StreamMock('content');
+        $stream->close();
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Stream is closed.');
+        $stream->read(5);
+    }
+
+    public function testGetContents(): void
+    {
+        $stream = new StreamMock('Hello World');
+
+        $result = $stream->getContents();
+
+        $this->assertSame('Hello World', $result);
+        $this->assertSame(11, $stream->getPosition());
+    }
+
+    public function testGetContentsFromPosition(): void
+    {
+        $stream = new StreamMock('Hello World', position: 6);
+
+        $result = $stream->getContents();
+
+        $this->assertSame('World', $result);
+    }
+
+    public function testGetContentsAtEof(): void
+    {
+        $stream = new StreamMock('Hello', position: 5);
+
+        $result = $stream->getContents();
+
+        $this->assertSame('', $result);
+    }
+
+    public function testGetMetadataDefault(): void
+    {
+        $stream = new StreamMock('Hello');
+
+        $metadata = $stream->getMetadata();
+
+        $this->assertIsArray($metadata);
+        $this->assertArrayHasKey('eof', $metadata);
+        $this->assertArrayHasKey('seekable', $metadata);
+        $this->assertFalse($metadata['eof']);
+        $this->assertTrue($metadata['seekable']);
+    }
+
+    public function testGetMetadataDefaultAtEof(): void
+    {
+        $stream = new StreamMock('Hello', position: 5);
+
+        $metadata = $stream->getMetadata();
+
+        $this->assertTrue($metadata['eof']);
+    }
+
+    public function testGetMetadataWithKey(): void
+    {
+        $stream = new StreamMock('Hello');
+
+        $this->assertFalse($stream->getMetadata('eof'));
+        $this->assertTrue($stream->getMetadata('seekable'));
+        $this->assertNull($stream->getMetadata('nonexistent'));
+    }
+
+    public function testGetMetadataWhenClosed(): void
+    {
+        $stream = new StreamMock('Hello');
+        $stream->close();
+
+        $this->assertSame([], $stream->getMetadata());
+        $this->assertNull($stream->getMetadata('eof'));
+    }
+
+    public function testGetMetadataWithArrayMetadata(): void
+    {
+        $customMetadata = [
+            'uri' => 'php://memory',
+            'mode' => 'r+',
+            'custom' => 'value',
+        ];
+        $stream = new StreamMock('Hello', metadata: $customMetadata);
+
+        $metadata = $stream->getMetadata();
+
+        $this->assertSame($customMetadata, $metadata);
+        $this->assertSame('php://memory', $stream->getMetadata('uri'));
+        $this->assertSame('value', $stream->getMetadata('custom'));
+        $this->assertNull($stream->getMetadata('nonexistent'));
+    }
+
+    public function testGetMetadataWithClosureMetadata(): void
+    {
+        $stream = new StreamMock(
+            'Hello',
+            position: 2,
+            metadata: static fn(StreamMock $s) => [
+                'position' => $s->getPosition(),
+                'size' => $s->getSize(),
+            ],
+        );
+
+        $metadata = $stream->getMetadata();
+
+        $this->assertSame(['position' => 2, 'size' => 5], $metadata);
+        $this->assertSame(2, $stream->getMetadata('position'));
+        $this->assertSame(5, $stream->getMetadata('size'));
+    }
+
+    public function testIsReadableWhenClosed(): void
+    {
+        $stream = new StreamMock();
+        $stream->close();
+
+        $this->assertFalse($stream->isReadable());
+    }
+
+    public function testIsWritableWhenClosed(): void
+    {
+        $stream = new StreamMock();
+        $stream->close();
+
+        $this->assertFalse($stream->isWritable());
+    }
+
+    public function testIsSeekableWhenClosed(): void
+    {
+        $stream = new StreamMock();
+        $stream->close();
+
+        $this->assertFalse($stream->isSeekable());
+    }
+
+    public function testMultipleReadOperations(): void
+    {
+        $stream = new StreamMock('Hello World');
+
+        $this->assertSame('Hello', $stream->read(5));
+        $this->assertSame(' ', $stream->read(1));
+        $this->assertSame('World', $stream->read(5));
+        $this->assertSame('', $stream->read(1));
+    }
+
+    public function testReadWriteCombination(): void
+    {
+        $stream = new StreamMock('Hello World');
+
+        $stream->read(6);
+        $stream->write('PHP');
+
+        $this->assertSame('Hello PHPld', (string) $stream);
+    }
+
+    public function testSeekReadCombination(): void
+    {
+        $stream = new StreamMock('Hello World');
+
+        $stream->seek(6);
+        $result = $stream->read(5);
+
+        $this->assertSame('World', $result);
+    }
+}

From f2c176af1b82344c733907a22abc16aa316d127e Mon Sep 17 00:00:00 2001
From: Sergei Predvoditelev <sergei@predvoditelev.ru>
Date: Tue, 3 Feb 2026 11:13:56 +0300
Subject: [PATCH 2/9] phpdoc

---
 src/HttpMessage/StreamMock.php | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/src/HttpMessage/StreamMock.php b/src/HttpMessage/StreamMock.php
index f5dfd08..6ae65ac 100644
--- a/src/HttpMessage/StreamMock.php
+++ b/src/HttpMessage/StreamMock.php
@@ -12,6 +12,10 @@
 use function strlen;
 
 /**
+ * A test-specific implementation of PSR-7 stream.
+ *
+ * Allows creating stream instances with configurable behavior for testing HTTP message handling.
+ *
  * @psalm-type MetadataClosure = Closure(StreamMock): array<string, mixed>
  */
 final class StreamMock implements StreamInterface
@@ -20,6 +24,14 @@ final class StreamMock implements StreamInterface
     private bool $detached = false;
 
     /**
+     * @param string $content Initial stream content.
+     * @param int $position Initial position of the stream pointer.
+     * @param bool $readable Whether the stream is readable.
+     * @param bool $writable Whether the stream is writable.
+     * @param bool $seekable Whether the stream is seekable.
+     * @param Closure|array|null $metadata Custom metadata as an array or a closure that receives
+     * the stream instance and returns an array.
+     *
      * @psalm-param MetadataClosure|array|null $metadata
      */
     public function __construct(
@@ -37,16 +49,25 @@ public function __toString(): string
         return $this->content;
     }
 
+    /**
+     * Checks whether the stream has been closed.
+     */
     public function isClosed(): bool
     {
         return $this->closed;
     }
 
+    /**
+     * Checks whether the stream has been detached.
+     */
     public function isDetached(): bool
     {
         return $this->detached;
     }
 
+    /**
+     * Returns the current position of the stream pointer.
+     */
     public function getPosition(): int
     {
         return $this->position;

From de3e7f81171bdc4e366452cf03a6e3fe61ee79dd Mon Sep 17 00:00:00 2001
From: StyleCI Bot <bot@styleci.io>
Date: Tue, 3 Feb 2026 08:14:11 +0000
Subject: [PATCH 3/9] Apply fixes from StyleCI

---
 src/HttpMessage/StreamMock.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/HttpMessage/StreamMock.php b/src/HttpMessage/StreamMock.php
index 6ae65ac..787936f 100644
--- a/src/HttpMessage/StreamMock.php
+++ b/src/HttpMessage/StreamMock.php
@@ -29,7 +29,7 @@ final class StreamMock implements StreamInterface
      * @param bool $readable Whether the stream is readable.
      * @param bool $writable Whether the stream is writable.
      * @param bool $seekable Whether the stream is seekable.
-     * @param Closure|array|null $metadata Custom metadata as an array or a closure that receives
+     * @param array|Closure|null $metadata Custom metadata as an array or a closure that receives
      * the stream instance and returns an array.
      *
      * @psalm-param MetadataClosure|array|null $metadata

From 1b612de719a3e3029c163a018794fd1c59cda75b Mon Sep 17 00:00:00 2001
From: Sergei Predvoditelev <sergei@predvoditelev.ru>
Date: Tue, 3 Feb 2026 13:26:25 +0300
Subject: [PATCH 4/9] rename

---
 CHANGELOG.md                                  |   2 +-
 docs/guide/en/README.md                       |  22 ++--
 .../{StreamMock.php => StringStream.php}      |   4 +-
 ...treamMockTest.php => StringStreamTest.php} | 114 +++++++++---------
 4 files changed, 71 insertions(+), 71 deletions(-)
 rename src/HttpMessage/{StreamMock.php => StringStream.php} (97%)
 rename tests/HttpMessage/{StreamMockTest.php => StringStreamTest.php} (78%)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b7c4385..4d3e771 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,7 +2,7 @@
 
 ## 3.1.1 under development
 
-- New #85: Add `StreamMock` (@vjik)
+- New #85: Add `StringStream` (@vjik)
 
 ## 3.1.0 December 01, 2025
 
diff --git a/docs/guide/en/README.md b/docs/guide/en/README.md
index a7a7ea2..4958b8b 100644
--- a/docs/guide/en/README.md
+++ b/docs/guide/en/README.md
@@ -130,16 +130,16 @@ sleep(10);
 echo $clock->now(); // Same value as above.
 ```
 
-## Stream mock [PSR-7](https://www.php-fig.org/psr/psr-7/) 
+## String stream [PSR-7](https://www.php-fig.org/psr/psr-7/) 
 
-The `StreamMock` class is a test-specific implementation of `StreamInterface`.
+The `StringStream` class is a test-specific implementation of `StreamInterface`.
 It allows you to create stream instances with configurable behavior for testing HTTP message handling.
 
 ```php
-use Yiisoft\Test\Support\HttpMessage\StreamMock;
+use Yiisoft\Test\Support\HttpMessage\StringStream;
 
 // Create a stream with content
-$stream = new StreamMock('Hello, World!');
+$stream = new StringStream('Hello, World!');
 
 echo $stream; // Hello, World!
 echo $stream->getSize(); // 13
@@ -151,13 +151,13 @@ You can configure stream behavior through constructor parameters:
 
 ```php
 // Create a read-only stream
-$readOnlyStream = new StreamMock('content', writable: false);
+$readOnlyStream = new StringStream('content', writable: false);
 
 // Create a non-seekable stream
-$nonSeekableStream = new StreamMock('content', seekable: false);
+$nonSeekableStream = new StringStream('content', seekable: false);
 
 // Create a stream with custom initial position
-$stream = new StreamMock('Hello', position: 3);
+$stream = new StringStream('Hello', position: 3);
 echo $stream->getContents(); // lo
 ```
 
@@ -165,7 +165,7 @@ Custom metadata can be provided as an array or a closure:
 
 ```php
 // Array metadata
-$stream = new StreamMock(
+$stream = new StringStream(
     'content',
     metadata: [
         'uri' => 'php://memory',
@@ -174,9 +174,9 @@ $stream = new StreamMock(
 );
 
 // Closure metadata (receives the stream instance)
-$stream = new StreamMock(
+$stream = new StringStream(
     'content', 
-    metadata: static fn(StreamMock $s) => [
+    metadata: static fn(StringStream $s) => [
         'size' => $s->getSize(),
         'eof' => $s->eof(),
     ],
@@ -186,7 +186,7 @@ $stream = new StreamMock(
 The stream provides helper methods to check its state:
 
 ```php
-$stream = new StreamMock('content');
+$stream = new StringStream('content');
 
 $stream->isClosed(); // false
 $stream->isDetached(); // false
diff --git a/src/HttpMessage/StreamMock.php b/src/HttpMessage/StringStream.php
similarity index 97%
rename from src/HttpMessage/StreamMock.php
rename to src/HttpMessage/StringStream.php
index 787936f..683be8f 100644
--- a/src/HttpMessage/StreamMock.php
+++ b/src/HttpMessage/StringStream.php
@@ -16,9 +16,9 @@
  *
  * Allows creating stream instances with configurable behavior for testing HTTP message handling.
  *
- * @psalm-type MetadataClosure = Closure(StreamMock): array<string, mixed>
+ * @psalm-type MetadataClosure = Closure(StringStream): array<string, mixed>
  */
-final class StreamMock implements StreamInterface
+final class StringStream implements StreamInterface
 {
     private bool $closed = false;
     private bool $detached = false;
diff --git a/tests/HttpMessage/StreamMockTest.php b/tests/HttpMessage/StringStreamTest.php
similarity index 78%
rename from tests/HttpMessage/StreamMockTest.php
rename to tests/HttpMessage/StringStreamTest.php
index 67c2a41..b086d6d 100644
--- a/tests/HttpMessage/StreamMockTest.php
+++ b/tests/HttpMessage/StringStreamTest.php
@@ -6,13 +6,13 @@
 
 use PHPUnit\Framework\TestCase;
 use RuntimeException;
-use Yiisoft\Test\Support\HttpMessage\StreamMock;
+use Yiisoft\Test\Support\HttpMessage\StringStream;
 
-final class StreamMockTest extends TestCase
+final class StringStreamTest extends TestCase
 {
     public function testBase(): void
     {
-        $stream = new StreamMock();
+        $stream = new StringStream();
 
         $this->assertSame(0, $stream->getSize());
         $this->assertSame(0, $stream->getPosition());
@@ -27,7 +27,7 @@ public function testBase(): void
 
     public function testConstructorWithContent(): void
     {
-        $stream = new StreamMock('Hello, World!');
+        $stream = new StringStream('Hello, World!');
 
         $this->assertSame('Hello, World!', (string) $stream);
         $this->assertSame(13, $stream->getSize());
@@ -35,7 +35,7 @@ public function testConstructorWithContent(): void
 
     public function testConstructorWithPosition(): void
     {
-        $stream = new StreamMock('Hello', position: 3);
+        $stream = new StringStream('Hello', position: 3);
 
         $this->assertSame(3, $stream->getPosition());
         $this->assertSame('lo', $stream->getContents());
@@ -43,35 +43,35 @@ public function testConstructorWithPosition(): void
 
     public function testConstructorWithReadableFlag(): void
     {
-        $stream = new StreamMock(readable: false);
+        $stream = new StringStream(readable: false);
 
         $this->assertFalse($stream->isReadable());
     }
 
     public function testConstructorWithWritableFlag(): void
     {
-        $stream = new StreamMock(writable: false);
+        $stream = new StringStream(writable: false);
 
         $this->assertFalse($stream->isWritable());
     }
 
     public function testConstructorWithSeekableFlag(): void
     {
-        $stream = new StreamMock(seekable: false);
+        $stream = new StringStream(seekable: false);
 
         $this->assertFalse($stream->isSeekable());
     }
 
     public function testToString(): void
     {
-        $stream = new StreamMock('Test content');
+        $stream = new StringStream('Test content');
 
         $this->assertSame('Test content', (string) $stream);
     }
 
     public function testClose(): void
     {
-        $stream = new StreamMock('content');
+        $stream = new StringStream('content');
 
         $this->assertFalse($stream->isClosed());
 
@@ -85,7 +85,7 @@ public function testClose(): void
 
     public function testDetach(): void
     {
-        $stream = new StreamMock('content');
+        $stream = new StringStream('content');
 
         $this->assertFalse($stream->isDetached());
 
@@ -98,28 +98,28 @@ public function testDetach(): void
 
     public function testGetSize(): void
     {
-        $stream = new StreamMock('');
+        $stream = new StringStream('');
         $this->assertSame(0, $stream->getSize());
 
-        $stream = new StreamMock('Hello');
+        $stream = new StringStream('Hello');
         $this->assertSame(5, $stream->getSize());
 
-        $stream = new StreamMock('Привет');
+        $stream = new StringStream('Привет');
         $this->assertSame(12, $stream->getSize()); // UTF-8 bytes
     }
 
     public function testTell(): void
     {
-        $stream = new StreamMock('Hello', position: 0);
+        $stream = new StringStream('Hello', position: 0);
         $this->assertSame(0, $stream->tell());
 
-        $stream = new StreamMock('Hello', position: 3);
+        $stream = new StringStream('Hello', position: 3);
         $this->assertSame(3, $stream->tell());
     }
 
     public function testTellThrowsExceptionWhenClosed(): void
     {
-        $stream = new StreamMock('Hello');
+        $stream = new StringStream('Hello');
         $stream->close();
 
         $this->expectException(RuntimeException::class);
@@ -129,19 +129,19 @@ public function testTellThrowsExceptionWhenClosed(): void
 
     public function testEof(): void
     {
-        $stream = new StreamMock('Hello', position: 0);
+        $stream = new StringStream('Hello', position: 0);
         $this->assertFalse($stream->eof());
 
-        $stream = new StreamMock('Hello', position: 5);
+        $stream = new StringStream('Hello', position: 5);
         $this->assertTrue($stream->eof());
 
-        $stream = new StreamMock('Hello', position: 10);
+        $stream = new StringStream('Hello', position: 10);
         $this->assertTrue($stream->eof());
     }
 
     public function testEofWhenClosed(): void
     {
-        $stream = new StreamMock('Hello');
+        $stream = new StringStream('Hello');
         $stream->close();
 
         $this->assertTrue($stream->eof());
@@ -149,7 +149,7 @@ public function testEofWhenClosed(): void
 
     public function testSeekSet(): void
     {
-        $stream = new StreamMock('Hello World');
+        $stream = new StringStream('Hello World');
 
         $stream->seek(5);
         $this->assertSame(5, $stream->getPosition());
@@ -160,7 +160,7 @@ public function testSeekSet(): void
 
     public function testSeekCur(): void
     {
-        $stream = new StreamMock('Hello World', position: 3);
+        $stream = new StringStream('Hello World', position: 3);
 
         $stream->seek(2, SEEK_CUR);
         $this->assertSame(5, $stream->getPosition());
@@ -171,7 +171,7 @@ public function testSeekCur(): void
 
     public function testSeekEnd(): void
     {
-        $stream = new StreamMock('Hello World');
+        $stream = new StringStream('Hello World');
 
         $stream->seek(0, SEEK_END);
         $this->assertSame(11, $stream->getPosition());
@@ -182,7 +182,7 @@ public function testSeekEnd(): void
 
     public function testSeekThrowsExceptionWhenNotSeekable(): void
     {
-        $stream = new StreamMock('Hello', seekable: false);
+        $stream = new StringStream('Hello', seekable: false);
 
         $this->expectException(RuntimeException::class);
         $this->expectExceptionMessage('Stream is not seekable.');
@@ -191,7 +191,7 @@ public function testSeekThrowsExceptionWhenNotSeekable(): void
 
     public function testSeekThrowsExceptionWhenClosed(): void
     {
-        $stream = new StreamMock('Hello');
+        $stream = new StringStream('Hello');
         $stream->close();
 
         $this->expectException(RuntimeException::class);
@@ -201,7 +201,7 @@ public function testSeekThrowsExceptionWhenClosed(): void
 
     public function testSeekThrowsExceptionForInvalidWhence(): void
     {
-        $stream = new StreamMock('Hello');
+        $stream = new StringStream('Hello');
 
         $this->expectException(RuntimeException::class);
         $this->expectExceptionMessage('Invalid whence value.');
@@ -210,7 +210,7 @@ public function testSeekThrowsExceptionForInvalidWhence(): void
 
     public function testSeekThrowsExceptionForNegativePosition(): void
     {
-        $stream = new StreamMock('Hello');
+        $stream = new StringStream('Hello');
 
         $this->expectException(RuntimeException::class);
         $this->expectExceptionMessage('Invalid seek position.');
@@ -219,7 +219,7 @@ public function testSeekThrowsExceptionForNegativePosition(): void
 
     public function testSeekThrowsExceptionForPositionBeyondSize(): void
     {
-        $stream = new StreamMock('Hello');
+        $stream = new StringStream('Hello');
 
         $this->expectException(RuntimeException::class);
         $this->expectExceptionMessage('Invalid seek position.');
@@ -228,7 +228,7 @@ public function testSeekThrowsExceptionForPositionBeyondSize(): void
 
     public function testRewind(): void
     {
-        $stream = new StreamMock('Hello', position: 5);
+        $stream = new StringStream('Hello', position: 5);
 
         $stream->rewind();
 
@@ -237,7 +237,7 @@ public function testRewind(): void
 
     public function testWrite(): void
     {
-        $stream = new StreamMock();
+        $stream = new StringStream();
 
         $bytesWritten = $stream->write('Hello');
 
@@ -248,7 +248,7 @@ public function testWrite(): void
 
     public function testWriteAtPosition(): void
     {
-        $stream = new StreamMock('Hello World', position: 6);
+        $stream = new StringStream('Hello World', position: 6);
 
         $stream->write('PHP');
 
@@ -258,7 +258,7 @@ public function testWriteAtPosition(): void
 
     public function testWriteOverwrite(): void
     {
-        $stream = new StreamMock('AAAAA', position: 0);
+        $stream = new StringStream('AAAAA', position: 0);
 
         $stream->write('BB');
 
@@ -267,7 +267,7 @@ public function testWriteOverwrite(): void
 
     public function testWriteThrowsExceptionWhenNotWritable(): void
     {
-        $stream = new StreamMock(writable: false);
+        $stream = new StringStream(writable: false);
 
         $this->expectException(RuntimeException::class);
         $this->expectExceptionMessage('Stream is not writable.');
@@ -276,7 +276,7 @@ public function testWriteThrowsExceptionWhenNotWritable(): void
 
     public function testWriteThrowsExceptionWhenClosed(): void
     {
-        $stream = new StreamMock();
+        $stream = new StringStream();
         $stream->close();
 
         $this->expectException(RuntimeException::class);
@@ -286,7 +286,7 @@ public function testWriteThrowsExceptionWhenClosed(): void
 
     public function testRead(): void
     {
-        $stream = new StreamMock('Hello World');
+        $stream = new StringStream('Hello World');
 
         $result = $stream->read(5);
 
@@ -296,7 +296,7 @@ public function testRead(): void
 
     public function testReadFromPosition(): void
     {
-        $stream = new StreamMock('Hello World', position: 6);
+        $stream = new StringStream('Hello World', position: 6);
 
         $result = $stream->read(5);
 
@@ -305,7 +305,7 @@ public function testReadFromPosition(): void
 
     public function testReadBeyondContent(): void
     {
-        $stream = new StreamMock('Hi');
+        $stream = new StringStream('Hi');
 
         $result = $stream->read(100);
 
@@ -315,7 +315,7 @@ public function testReadBeyondContent(): void
 
     public function testReadAtEof(): void
     {
-        $stream = new StreamMock('Hello', position: 5);
+        $stream = new StringStream('Hello', position: 5);
 
         $result = $stream->read(10);
 
@@ -324,7 +324,7 @@ public function testReadAtEof(): void
 
     public function testReadThrowsExceptionWhenNotReadable(): void
     {
-        $stream = new StreamMock('content', readable: false);
+        $stream = new StringStream('content', readable: false);
 
         $this->expectException(RuntimeException::class);
         $this->expectExceptionMessage('Stream is not readable.');
@@ -333,7 +333,7 @@ public function testReadThrowsExceptionWhenNotReadable(): void
 
     public function testReadThrowsExceptionWhenClosed(): void
     {
-        $stream = new StreamMock('content');
+        $stream = new StringStream('content');
         $stream->close();
 
         $this->expectException(RuntimeException::class);
@@ -343,7 +343,7 @@ public function testReadThrowsExceptionWhenClosed(): void
 
     public function testGetContents(): void
     {
-        $stream = new StreamMock('Hello World');
+        $stream = new StringStream('Hello World');
 
         $result = $stream->getContents();
 
@@ -353,7 +353,7 @@ public function testGetContents(): void
 
     public function testGetContentsFromPosition(): void
     {
-        $stream = new StreamMock('Hello World', position: 6);
+        $stream = new StringStream('Hello World', position: 6);
 
         $result = $stream->getContents();
 
@@ -362,7 +362,7 @@ public function testGetContentsFromPosition(): void
 
     public function testGetContentsAtEof(): void
     {
-        $stream = new StreamMock('Hello', position: 5);
+        $stream = new StringStream('Hello', position: 5);
 
         $result = $stream->getContents();
 
@@ -371,7 +371,7 @@ public function testGetContentsAtEof(): void
 
     public function testGetMetadataDefault(): void
     {
-        $stream = new StreamMock('Hello');
+        $stream = new StringStream('Hello');
 
         $metadata = $stream->getMetadata();
 
@@ -384,7 +384,7 @@ public function testGetMetadataDefault(): void
 
     public function testGetMetadataDefaultAtEof(): void
     {
-        $stream = new StreamMock('Hello', position: 5);
+        $stream = new StringStream('Hello', position: 5);
 
         $metadata = $stream->getMetadata();
 
@@ -393,7 +393,7 @@ public function testGetMetadataDefaultAtEof(): void
 
     public function testGetMetadataWithKey(): void
     {
-        $stream = new StreamMock('Hello');
+        $stream = new StringStream('Hello');
 
         $this->assertFalse($stream->getMetadata('eof'));
         $this->assertTrue($stream->getMetadata('seekable'));
@@ -402,7 +402,7 @@ public function testGetMetadataWithKey(): void
 
     public function testGetMetadataWhenClosed(): void
     {
-        $stream = new StreamMock('Hello');
+        $stream = new StringStream('Hello');
         $stream->close();
 
         $this->assertSame([], $stream->getMetadata());
@@ -416,7 +416,7 @@ public function testGetMetadataWithArrayMetadata(): void
             'mode' => 'r+',
             'custom' => 'value',
         ];
-        $stream = new StreamMock('Hello', metadata: $customMetadata);
+        $stream = new StringStream('Hello', metadata: $customMetadata);
 
         $metadata = $stream->getMetadata();
 
@@ -428,10 +428,10 @@ public function testGetMetadataWithArrayMetadata(): void
 
     public function testGetMetadataWithClosureMetadata(): void
     {
-        $stream = new StreamMock(
+        $stream = new StringStream(
             'Hello',
             position: 2,
-            metadata: static fn(StreamMock $s) => [
+            metadata: static fn(StringStream $s) => [
                 'position' => $s->getPosition(),
                 'size' => $s->getSize(),
             ],
@@ -446,7 +446,7 @@ public function testGetMetadataWithClosureMetadata(): void
 
     public function testIsReadableWhenClosed(): void
     {
-        $stream = new StreamMock();
+        $stream = new StringStream();
         $stream->close();
 
         $this->assertFalse($stream->isReadable());
@@ -454,7 +454,7 @@ public function testIsReadableWhenClosed(): void
 
     public function testIsWritableWhenClosed(): void
     {
-        $stream = new StreamMock();
+        $stream = new StringStream();
         $stream->close();
 
         $this->assertFalse($stream->isWritable());
@@ -462,7 +462,7 @@ public function testIsWritableWhenClosed(): void
 
     public function testIsSeekableWhenClosed(): void
     {
-        $stream = new StreamMock();
+        $stream = new StringStream();
         $stream->close();
 
         $this->assertFalse($stream->isSeekable());
@@ -470,7 +470,7 @@ public function testIsSeekableWhenClosed(): void
 
     public function testMultipleReadOperations(): void
     {
-        $stream = new StreamMock('Hello World');
+        $stream = new StringStream('Hello World');
 
         $this->assertSame('Hello', $stream->read(5));
         $this->assertSame(' ', $stream->read(1));
@@ -480,7 +480,7 @@ public function testMultipleReadOperations(): void
 
     public function testReadWriteCombination(): void
     {
-        $stream = new StreamMock('Hello World');
+        $stream = new StringStream('Hello World');
 
         $stream->read(6);
         $stream->write('PHP');
@@ -490,7 +490,7 @@ public function testReadWriteCombination(): void
 
     public function testSeekReadCombination(): void
     {
-        $stream = new StreamMock('Hello World');
+        $stream = new StringStream('Hello World');
 
         $stream->seek(6);
         $result = $stream->read(5);

From 93331775cdfb1f06408319de8f6c0ba74322d506 Mon Sep 17 00:00:00 2001
From: Sergei Predvoditelev <sergei@predvoditelev.ru>
Date: Thu, 5 Feb 2026 12:54:36 +0300
Subject: [PATCH 5/9] Update docs/guide/en/README.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 docs/guide/en/README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/guide/en/README.md b/docs/guide/en/README.md
index 4958b8b..dcfe82b 100644
--- a/docs/guide/en/README.md
+++ b/docs/guide/en/README.md
@@ -130,7 +130,7 @@ sleep(10);
 echo $clock->now(); // Same value as above.
 ```
 
-## String stream [PSR-7](https://www.php-fig.org/psr/psr-7/) 
+## String stream [PSR-7](https://www.php-fig.org/psr/psr-7/)
 
 The `StringStream` class is a test-specific implementation of `StreamInterface`.
 It allows you to create stream instances with configurable behavior for testing HTTP message handling.

From 6dbbf1281ddca2c5ce8259ecdf7555b9b23b93fa Mon Sep 17 00:00:00 2001
From: Sergei Predvoditelev <sergei@predvoditelev.ru>
Date: Thu, 5 Feb 2026 12:54:45 +0300
Subject: [PATCH 6/9] Update docs/guide/en/README.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 docs/guide/en/README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/guide/en/README.md b/docs/guide/en/README.md
index dcfe82b..90fdd6c 100644
--- a/docs/guide/en/README.md
+++ b/docs/guide/en/README.md
@@ -175,7 +175,7 @@ $stream = new StringStream(
 
 // Closure metadata (receives the stream instance)
 $stream = new StringStream(
-    'content', 
+    'content',
     metadata: static fn(StringStream $s) => [
         'size' => $s->getSize(),
         'eof' => $s->eof(),

From de89fefceb8a5a9b87a9028813e92334ad69360f Mon Sep 17 00:00:00 2001
From: Sergei Predvoditelev <sergei@predvoditelev.ru>
Date: Thu, 5 Feb 2026 12:59:17 +0300
Subject: [PATCH 7/9] test

---
 src/HttpMessage/StringStream.php       |  2 +-
 tests/HttpMessage/StringStreamTest.php | 76 ++++++++++++++++++++++++++
 2 files changed, 77 insertions(+), 1 deletion(-)

diff --git a/src/HttpMessage/StringStream.php b/src/HttpMessage/StringStream.php
index 683be8f..c3e4cfc 100644
--- a/src/HttpMessage/StringStream.php
+++ b/src/HttpMessage/StringStream.php
@@ -159,7 +159,7 @@ public function write(string $string): int
         $this->content = substr($this->content, 0, $this->position)
             . $string
             . substr($this->content, $this->position + $size);
-        $this->position += $size;
+        $this->position = min($this->position + $size, $this->getContentSize());
 
         return $size;
     }
diff --git a/tests/HttpMessage/StringStreamTest.php b/tests/HttpMessage/StringStreamTest.php
index b086d6d..20e0d9d 100644
--- a/tests/HttpMessage/StringStreamTest.php
+++ b/tests/HttpMessage/StringStreamTest.php
@@ -69,6 +69,22 @@ public function testToString(): void
         $this->assertSame('Test content', (string) $stream);
     }
 
+    public function testToStringWhenClosed(): void
+    {
+        $stream = new StringStream('Test content');
+        $stream->close();
+
+        $this->assertSame('Test content', (string) $stream);
+    }
+
+    public function testToStringWhenDetached(): void
+    {
+        $stream = new StringStream('Test content');
+        $stream->detach();
+
+        $this->assertSame('Test content', (string) $stream);
+    }
+
     public function testClose(): void
     {
         $stream = new StringStream('content');
@@ -235,6 +251,25 @@ public function testRewind(): void
         $this->assertSame(0, $stream->getPosition());
     }
 
+    public function testRewindThrowsExceptionWhenNotSeekable(): void
+    {
+        $stream = new StringStream('Hello', seekable: false);
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Stream is not seekable.');
+        $stream->rewind();
+    }
+
+    public function testRewindThrowsExceptionWhenClosed(): void
+    {
+        $stream = new StringStream('Hello');
+        $stream->close();
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Stream is closed.');
+        $stream->rewind();
+    }
+
     public function testWrite(): void
     {
         $stream = new StringStream();
@@ -265,6 +300,28 @@ public function testWriteOverwrite(): void
         $this->assertSame('BBAAA', (string) $stream);
     }
 
+    public function testWriteAtEndOfContent(): void
+    {
+        $stream = new StringStream('Hello', position: 5);
+
+        $bytesWritten = $stream->write(' World');
+
+        $this->assertSame(6, $bytesWritten);
+        $this->assertSame('Hello World', (string) $stream);
+        $this->assertSame(11, $stream->getPosition());
+    }
+
+    public function testWriteBeyondContent(): void
+    {
+        $stream = new StringStream('Hi', position: 10);
+
+        $bytesWritten = $stream->write('!');
+
+        $this->assertSame(1, $bytesWritten);
+        $this->assertSame('Hi!', (string) $stream);
+        $this->assertSame(3, $stream->getPosition());
+    }
+
     public function testWriteThrowsExceptionWhenNotWritable(): void
     {
         $stream = new StringStream(writable: false);
@@ -369,6 +426,25 @@ public function testGetContentsAtEof(): void
         $this->assertSame('', $result);
     }
 
+    public function testGetContentsThrowsExceptionWhenNotReadable(): void
+    {
+        $stream = new StringStream('content', readable: false);
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Stream is not readable.');
+        $stream->getContents();
+    }
+
+    public function testGetContentsThrowsExceptionWhenClosed(): void
+    {
+        $stream = new StringStream('content');
+        $stream->close();
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Stream is closed.');
+        $stream->getContents();
+    }
+
     public function testGetMetadataDefault(): void
     {
         $stream = new StringStream('Hello');

From ca989811ce829611506e49b9e02a3a815eb55e52 Mon Sep 17 00:00:00 2001
From: Sergei Predvoditelev <sergei@predvoditelev.ru>
Date: Thu, 5 Feb 2026 13:10:51 +0300
Subject: [PATCH 8/9] improve

---
 src/HttpMessage/StringStream.php       |  7 +++++++
 tests/HttpMessage/StringStreamTest.php | 29 +++++++++++++-------------
 2 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/src/HttpMessage/StringStream.php b/src/HttpMessage/StringStream.php
index c3e4cfc..01217a1 100644
--- a/src/HttpMessage/StringStream.php
+++ b/src/HttpMessage/StringStream.php
@@ -7,6 +7,7 @@
 use Closure;
 use Psr\Http\Message\StreamInterface;
 use RuntimeException;
+use LogicException;
 
 use function is_array;
 use function strlen;
@@ -42,6 +43,12 @@ public function __construct(
         private bool $seekable = true,
         private Closure|array|null $metadata = null,
     ) {
+        $size = strlen($this->content);
+        if ($this->position < 0 || $this->position > $size) {
+            throw new LogicException(
+                sprintf('Position %d is out of valid range [0, %d].', $this->position, $size)
+            );
+        }
     }
 
     public function __toString(): string
diff --git a/tests/HttpMessage/StringStreamTest.php b/tests/HttpMessage/StringStreamTest.php
index 20e0d9d..1472b5c 100644
--- a/tests/HttpMessage/StringStreamTest.php
+++ b/tests/HttpMessage/StringStreamTest.php
@@ -4,6 +4,7 @@
 
 namespace Yiisoft\Test\Support\Tests\HttpMessage;
 
+use LogicException;
 use PHPUnit\Framework\TestCase;
 use RuntimeException;
 use Yiisoft\Test\Support\HttpMessage\StringStream;
@@ -62,6 +63,20 @@ public function testConstructorWithSeekableFlag(): void
         $this->assertFalse($stream->isSeekable());
     }
 
+    public function testConstructorThrowsExceptionForNegativePosition(): void
+    {
+        $this->expectException(LogicException::class);
+        $this->expectExceptionMessage('Position -1 is out of valid range [0, 5].');
+        new StringStream('Hello', position: -1);
+    }
+
+    public function testConstructorThrowsExceptionForPositionBeyondContent(): void
+    {
+        $this->expectException(LogicException::class);
+        $this->expectExceptionMessage('Position 10 is out of valid range [0, 5].');
+        new StringStream('Hello', position: 10);
+    }
+
     public function testToString(): void
     {
         $stream = new StringStream('Test content');
@@ -150,9 +165,6 @@ public function testEof(): void
 
         $stream = new StringStream('Hello', position: 5);
         $this->assertTrue($stream->eof());
-
-        $stream = new StringStream('Hello', position: 10);
-        $this->assertTrue($stream->eof());
     }
 
     public function testEofWhenClosed(): void
@@ -311,17 +323,6 @@ public function testWriteAtEndOfContent(): void
         $this->assertSame(11, $stream->getPosition());
     }
 
-    public function testWriteBeyondContent(): void
-    {
-        $stream = new StringStream('Hi', position: 10);
-
-        $bytesWritten = $stream->write('!');
-
-        $this->assertSame(1, $bytesWritten);
-        $this->assertSame('Hi!', (string) $stream);
-        $this->assertSame(3, $stream->getPosition());
-    }
-
     public function testWriteThrowsExceptionWhenNotWritable(): void
     {
         $stream = new StringStream(writable: false);

From 1b0401ea802a55c58282a779f10b047c35d33a53 Mon Sep 17 00:00:00 2001
From: Sergei Predvoditelev <sergei@predvoditelev.ru>
Date: Thu, 5 Feb 2026 13:12:25 +0300
Subject: [PATCH 9/9] improve

---
 src/HttpMessage/StringStream.php       | 4 ++++
 tests/HttpMessage/StringStreamTest.php | 9 +++++++++
 2 files changed, 13 insertions(+)

diff --git a/src/HttpMessage/StringStream.php b/src/HttpMessage/StringStream.php
index 01217a1..faeb473 100644
--- a/src/HttpMessage/StringStream.php
+++ b/src/HttpMessage/StringStream.php
@@ -186,6 +186,10 @@ public function read(int $length): string
             throw new RuntimeException('Stream is closed.');
         }
 
+        if ($length < 0) {
+            throw new RuntimeException('Length cannot be negative.');
+        }
+
         if ($this->position >= $this->getContentSize()) {
             return '';
         }
diff --git a/tests/HttpMessage/StringStreamTest.php b/tests/HttpMessage/StringStreamTest.php
index 1472b5c..ca3b3f2 100644
--- a/tests/HttpMessage/StringStreamTest.php
+++ b/tests/HttpMessage/StringStreamTest.php
@@ -399,6 +399,15 @@ public function testReadThrowsExceptionWhenClosed(): void
         $stream->read(5);
     }
 
+    public function testReadThrowsExceptionForNegativeLength(): void
+    {
+        $stream = new StringStream('content');
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Length cannot be negative.');
+        $stream->read(-1);
+    }
+
     public function testGetContents(): void
     {
         $stream = new StringStream('Hello World');