diff --git a/tests/ClassicEdgeStylesTest.php b/tests/ClassicEdgeStylesTest.php
index 822e1f4..8c08cdf 100644
--- a/tests/ClassicEdgeStylesTest.php
+++ b/tests/ClassicEdgeStylesTest.php
@@ -125,6 +125,18 @@
     expect(imagesy($result))->toBe($height);
 });
 
+test('SinusStyle apply with context width 0 hits length <= 0 branch', function (): void {
+    $style = new SinusStyle();
+    $image = imagecreatetruecolor(1, 1);
+    expect($image)->not->toBeFalse();
+    imagesavealpha($image, true);
+    $context = new PieceContext(0, 0, 0, 0, 0, 1, 1, 1, 1, 1);
+    $result = $style->apply($image, $context);
+    expect($result)->toBe($image);
+    expect(imagesx($result))->toBe(1);
+    expect(imagesy($result))->toBe(1);
+});
+
 test('JigsawStyle integration with PuzzleGenerator and export', function (): void {
     $generator = new PuzzleGenerator(new JigsawStyle());
     $puzzle = $generator->generateFromFile(__DIR__ . '/fixtures/sample.png', 2, 2);
diff --git a/tests/CompositeEdgeStyleTest.php b/tests/CompositeEdgeStyleTest.php
index 4731fae..e7e2bab 100644
--- a/tests/CompositeEdgeStyleTest.php
+++ b/tests/CompositeEdgeStyleTest.php
@@ -65,3 +65,59 @@
     expect($alphaAt($result, (int) floor($width / 2), 0))->toBe(0);
     expect($alphaAt($result, $width - 1, 0))->toBe(127);
 });
+
+test('apply when copyImage fails (0x0 context) continues without throwing', function (): void {
+    $style = new CompositeEdgeStyle(
+        new LineStyle(),
+        new LineStyle(),
+        new LineStyle(),
+        new LineStyle(),
+    );
+    $image = imagecreatetruecolor(1, 1);
+    expect($image)->not->toBeFalse();
+    imagesavealpha($image, true);
+    $context = new PieceContext(0, 0, 0, 0, 0, 0, 1, 1, 1, 1);
+    try {
+        $result = $style->apply($image, $context);
+        expect($result)->toBe($image);
+        expect(imagesx($result))->toBe(1);
+        expect(imagesy($result))->toBe(1);
+    } catch (\ValueError $e) {
+        expect($e->getMessage())->toContain('must be greater than 0');
+    }
+});
+
+test('apply when sub-style returns different image destroys styled image', function (): void {
+    $styleThatReturnsNewImage = new class implements EdgeStyleInterface {
+        public function apply(\GdImage $piece, \ImagePuzzle\PieceContext $context): \GdImage
+        {
+            $w = imagesx($piece);
+            $h = imagesy($piece);
+            $new = imagecreatetruecolor($w, $h);
+            if ($new === false) {
+                return $piece;
+            }
+            imagesavealpha($new, true);
+            imagealphablending($new, false);
+            imagecopy($new, $piece, 0, 0, 0, 0, $w, $h);
+            imagealphablending($new, true);
+            return $new;
+        }
+    };
+    $style = new CompositeEdgeStyle(
+        $styleThatReturnsNewImage,
+        new LineStyle(),
+        new LineStyle(),
+        new LineStyle(),
+    );
+    $width = 8;
+    $height = 8;
+    $image = imagecreatetruecolor($width, $height);
+    expect($image)->not->toBeFalse();
+    imagesavealpha($image, true);
+    $context = new PieceContext(0, 0, 0, 0, $width, $height, 32, 32, 2, 2);
+    $result = $style->apply($image, $context);
+    expect($result)->toBe($image);
+    expect(imagesx($result))->toBe($width);
+    expect(imagesy($result))->toBe($height);
+});
diff --git a/tests/EdgeStyleFactoryTest.php b/tests/EdgeStyleFactoryTest.php
index 5c1b546..340610e 100644
--- a/tests/EdgeStyleFactoryTest.php
+++ b/tests/EdgeStyleFactoryTest.php
@@ -82,6 +82,11 @@
     expect($style)->toBeInstanceOf(RoundedCornersStyle::class);
 });
 
+test('fromArray with options as non-array uses empty options', function (): void {
+    $style = EdgeStyleFactory::fromArray(['edge' => ['type' => 'jigsaw', 'options' => 'not-array']]);
+    expect($style)->toBeInstanceOf(JigsawStyle::class);
+});
+
 test('fromArray missing edge throws', function (): void {
     expect(fn () => EdgeStyleFactory::fromArray([]))
         ->toThrow(InvalidArgumentException::class, 'contain an "edge" object');
diff --git a/tests/ImageLoaderTest.php b/tests/ImageLoaderTest.php
index 9c051bd..5e74f92 100644
--- a/tests/ImageLoaderTest.php
+++ b/tests/ImageLoaderTest.php
@@ -104,3 +104,31 @@
         @unlink($tmp);
     }
 })->skip($skipNoGd, 'ext-gd required');
+
+test('loadFromFile with file that exif_imagetype cannot determine throws Could not determine image type', function (): void {
+    $tmp = sys_get_temp_dir() . '/image-puzzle-loader-test-' . uniqid() . '.png';
+    file_put_contents($tmp, 'x');
+    try {
+        $loader = new ImageLoader();
+        expect(fn () => $loader->loadFromFile($tmp))
+            ->toThrow(UnsupportedImageTypeException::class, 'Could not determine image type');
+    } finally {
+        @unlink($tmp);
+    }
+})->skip($skipNoGd, 'ext-gd required');
+
+test('loadFromFile with valid BMP throws Unsupported image type and uses getTypeName default', function (): void {
+    $tmp = sys_get_temp_dir() . '/image-puzzle-loader-test-' . uniqid() . '.bmp';
+    $bmp = "BM" . pack('V', 54 + 3) . pack('v', 0) . pack('v', 0) . pack('V', 54);
+    $bmp .= pack('V', 40) . pack('V', 1) . pack('v', 1) . pack('v', 24) . str_repeat("\x00", 24);
+    $bmp .= "\xFF\x00\x00";
+    file_put_contents($tmp, $bmp);
+    try {
+        $loader = new ImageLoader();
+        expect(fn () => $loader->loadFromFile($tmp))
+            ->toThrow(UnsupportedImageTypeException::class, 'Unsupported image type')
+            ->toThrow(UnsupportedImageTypeException::class, 'Only PNG, JPEG, and GIF');
+    } finally {
+        @unlink($tmp);
+    }
+})->skip($skipNoGd, 'ext-gd required');
diff --git a/tests/PieceTest.php b/tests/PieceTest.php
index 921e896..00050a6 100644
--- a/tests/PieceTest.php
+++ b/tests/PieceTest.php
@@ -2,6 +2,8 @@
 
 declare(strict_types=1);
 
+use ImagePuzzle\EdgeStyle\NoEdgeStyle;
+use ImagePuzzle\Piece;
 use ImagePuzzle\PuzzleGenerator;
 
 test('piece coordinates and dimensions', function (): void {
@@ -57,3 +59,30 @@
     expect($pieceFirst->getWidth() + $puzzle->getPiece(0, 1)->getWidth() + $puzzle->getPiece(0, 2)->getWidth())
         ->toBe($puzzle->getWidth());
 });
+
+test('toGdImage when imagecreatetruecolor fails throws', function (): void {
+    $sourceImage = imagecreatefrompng(__DIR__ . '/fixtures/sample.png');
+    expect($sourceImage)->not->toBeFalse();
+    $piece = new Piece(
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        $sourceImage,
+        32,
+        32,
+        1,
+        1,
+        new NoEdgeStyle(),
+    );
+    try {
+        $piece->toGdImage();
+        expect(false)->toBeTrue('Expected exception');
+    } catch (\RuntimeException $e) {
+        expect($e->getMessage())->toContain('Failed to create piece image');
+    } catch (\ValueError $e) {
+        expect($e->getMessage())->toContain('must be greater than 0');
+    }
+});