diff --git a/.travis.yml b/.travis.yml
index 6f88ce5..a24d15c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,21 +8,21 @@ php:
 
 dist: trusty
 
-before_install:
-  - composer selfupdate
-
 install:
   - composer install --prefer-source --dev
+  - wget https://github.com/infection/infection/releases/download/0.7.0/infection.phar
+  - wget https://github.com/infection/infection/releases/download/0.7.0/infection.phar.pubkey
+  - chmod +x infection.phar
 
 script:
   - php vendor/bin/phpunit
-  - vendor/bin/phpstan analyze -l 4 src tests examples
   - php vendor/bin/phpcs -n --standard=PSR1,PSR2 --report=full src/ tests/ examples/
+  - if [ "$TRAVIS_PHP_VERSION" != "nightly" ]; then php infection.phar --min-msi=75 --min-covered-msi=75 --threads=4; fi
+  - php vendor/bin/phpstan analyze -l 4 src tests examples
   - ./validate_examples.sh
 
 after_success:
-  - wget https://scrutinizer-ci.com/ocular.phar
-  - sh -c 'if [ "$TRAVIS_PHP_VERSION" != "hhvm" ] && [ "$TRAVIS_PHP_VERSION" != "nightly" ]; then php ocular.phar code-coverage:upload --format=php-clover build/docs/clover.xml; fi;'
+  - if [ "$TRAVIS_PHP_VERSION" != "nightly" ]; then php ocular.phar code-coverage:upload --format=php-clover build/docs/clover.xml; fi
 
 matrix:
     fast_finish: true
diff --git a/infection.json.dist b/infection.json.dist
new file mode 100644
index 0000000..b883a21
--- /dev/null
+++ b/infection.json.dist
@@ -0,0 +1,11 @@
+{
+    "timeout": 10,
+    "source": {
+        "directories": [
+            "src"
+        ]
+    },
+    "logs": {
+        "text": "infection-log.txt"
+    }
+}
\ No newline at end of file
diff --git a/src/Buffertools/Parser.php b/src/Buffertools/Parser.php
index 1565bbe..ee0998e 100644
--- a/src/Buffertools/Parser.php
+++ b/src/Buffertools/Parser.php
@@ -11,7 +11,7 @@ class Parser
     /**
      * @var string
      */
-    private $string;
+    private $string = '';
 
     /**
      * @var int
@@ -26,25 +26,15 @@ class Parser
     /**
      * Instantiate class, optionally taking Buffer or HEX.
      *
-     * @param null|string|BufferInterface $input
+     * @param BufferInterface $input
      */
-    public function __construct($input = null)
+    public function __construct(BufferInterface $input = null)
     {
-        if (null === $input) {
-            $input = '';
+        if ($input instanceof BufferInterface) {
+            $this->string = $input->getBinary();
+            $this->size = $input->getSize();
+            assert(strlen($this->string) === $this->size);
         }
-
-        if (is_string($input)) {
-            $bin = Buffer::hex($input, null)->getBinary();
-        } elseif ($input instanceof BufferInterface) {
-            $bin = $input->getBinary();
-        } else {
-            throw new \InvalidArgumentException("Invalid argument to Parser");
-        }
-
-        $this->string = $bin;
-        $this->position = 0;
-        $this->size = strlen($this->string);
     }
 
     /**
@@ -96,64 +86,6 @@ public function readBytes(int $numBytes, bool $flipBytes = false): BufferInterfa
         return new Buffer($string, $length);
     }
 
-    /**
-     * Write $data as $bytes bytes. Can be flipped if needed.
-     *
-     * @param  integer $numBytes - number of bytes to write
-     * @param  SerializableInterface|BufferInterface|string $data - buffer, serializable or hex
-     * @param  bool $flipBytes
-     * @return Parser
-     */
-    public function writeBytes(int $numBytes, $data, bool $flipBytes = false): Parser
-    {
-        // Treat $data to ensure it's a buffer, with the correct size
-        if ($data instanceof SerializableInterface) {
-            $data = $data->getBuffer();
-        }
-
-        if (is_string($data)) {
-            // Convert to a buffer
-            $data = Buffer::hex($data, $numBytes);
-        } else if (!($data instanceof BufferInterface)) {
-            throw new \RuntimeException('Invalid data passed to Parser::writeBytes');
-        }
-
-        $this->writeBuffer($numBytes, $data, $flipBytes);
-
-        return $this;
-    }
-
-    /**
-     * Write $data as $bytes bytes. Can be flipped if needed.
-     *
-     * @param  integer $numBytes
-     * @param  string $data
-     * @param  bool $flipBytes
-     * @return Parser
-     */
-    public function writeRawBinary(int $numBytes, string $data, bool $flipBytes = false): Parser
-    {
-        return $this->writeBuffer($numBytes, new Buffer($data, $numBytes), $flipBytes);
-    }
-
-    /**
-     * @param BufferInterface $buffer
-     * @param bool $flipBytes
-     * @param int $numBytes
-     * @return Parser
-     */
-    public function writeBuffer(int $numBytes, BufferInterface $buffer, bool $flipBytes = false): Parser
-    {
-        // only create a new buffer if the size does not match
-        if ($buffer->getSize() != $numBytes) {
-            $buffer = new Buffer($buffer->getBinary(), $numBytes);
-        }
-
-        $this->appendBuffer($buffer, $flipBytes);
-
-        return $this;
-    }
-
     /**
      * @param BufferInterface $buffer
      * @param bool $flipBytes
@@ -195,7 +127,7 @@ public function writeArray(array $serializable): Parser
             }
 
             if ($object instanceof BufferInterface) {
-                $parser->writeBytes($object->getSize(), $object);
+                $parser->appendBinary($object->getBinary());
             } else {
                 throw new \RuntimeException('Input to writeArray must be Buffer[], or SerializableInterface[]');
             }
@@ -214,6 +146,6 @@ public function writeArray(array $serializable): Parser
      */
     public function getBuffer(): BufferInterface
     {
-        return new Buffer($this->string, null);
+        return new Buffer($this->string, $this->size);
     }
 }
diff --git a/src/Buffertools/Template.php b/src/Buffertools/Template.php
index bc57afa..4df2d97 100644
--- a/src/Buffertools/Template.php
+++ b/src/Buffertools/Template.php
@@ -63,7 +63,7 @@ public function addItem(TypeInterface $item): Template
      */
     public function parse(Parser $parser): array
     {
-        if (0 == count($this->template)) {
+        if (empty($this->template)) {
             throw new \RuntimeException('No items in template');
         }
 
diff --git a/src/Buffertools/Types/ByteString.php b/src/Buffertools/Types/ByteString.php
index 2df9cc5..b273867 100644
--- a/src/Buffertools/Types/ByteString.php
+++ b/src/Buffertools/Types/ByteString.php
@@ -43,7 +43,7 @@ public function writeBits(BufferInterface $string): string
     }
 
     /**
-     * @param Buffer $string
+     * @param BufferInterface $string
      * @return string
      * @throws \Exception
      */
@@ -84,7 +84,7 @@ public function readBits(BufferInterface $buffer): string
     /**
      * @param Parser $parser
      * @return BufferInterface
-     * @throws \BitWasp\Buffertools\Exceptions\ParserOutOfRange
+     * @throws \Exception
      */
     public function read(Parser $parser): BufferInterface
     {
diff --git a/tests/ParserTest.php b/tests/ParserTest.php
index e2dbc36..4a2ac8d 100644
--- a/tests/ParserTest.php
+++ b/tests/ParserTest.php
@@ -16,6 +16,7 @@ public function testParserEmpty()
         $this->assertInstanceOf(Parser::class, $parser);
 
         $this->assertSame(0, $parser->getPosition());
+        $this->assertSame(0, $parser->getSize());
         $this->assertInstanceOf(Buffer::class, $parser->getBuffer());
         $this->assertEmpty($parser->getBuffer()->getHex());
     }
@@ -23,9 +24,10 @@ public function testParserEmpty()
     public function testGetBuffer()
     {
         $buffer = Buffer::hex('41414141');
-
         $parser = new Parser($buffer);
-        $this->assertSame($parser->getBuffer()->getBinary(), $buffer->getBinary());
+        $this->assertSame(0, $parser->getPosition());
+        $this->assertSame($buffer->getBinary(), $parser->getBuffer()->getBinary());
+        $this->assertEquals($buffer->getSize(), $parser->getSize());
     }
 
     public function testGetBufferEmptyNull()
@@ -39,58 +41,67 @@ public function testGetBufferEmptyNull()
 
     public function testWriteBytes()
     {
-        $bytes = '41424344';
+        $bytes = Buffer::hex('41424344');
+
         $parser = new Parser();
-        $parser->writeBytes(4, Buffer::hex($bytes));
-        $returned = $parser->getBuffer()->getHex();
-        $this->assertSame($returned, '41424344');
+        $this->assertEquals(0, $parser->getSize());
+        $this->assertEquals(0, $parser->getPosition());
+        $parser->appendBuffer($bytes);
+        $this->assertEquals(4, $parser->getSize());
+        $this->assertEquals(0, $parser->getPosition());
+
+        $this->assertTrue($parser->getBuffer()->equals($bytes));
+
+        $bytesAgain = $parser->readBytes(4);
+
+        $this->assertEquals(4, $parser->getSize());
+        $this->assertEquals(4, $parser->getPosition());
+        $this->assertTrue($bytesAgain->equals($bytes));
     }
 
     public function testWriteBytesFlip()
     {
-        $bytes = '41424344';
+        $bytes = Buffer::hex('41424344');
         $parser = new Parser();
-        $parser->writeBytes(4, Buffer::hex($bytes), true);
-        $returned = $parser->getBuffer()->getHex();
-        $this->assertSame($returned, '44434241');
+        $parser->appendBuffer($bytes, true);
+
+        $this->assertEquals('44434241', $parser->getBuffer()->getHex());
     }
 
     public function testWriteBytesPadded()
     {
         $parser = new Parser();
-        $parser->writeBytes(4, Buffer::hex('34'));
+        $parser->appendBuffer(Buffer::hex('34'));
         $this->assertEquals("00000034", $parser->getBuffer()->getHex());
     }
 
     public function testWriteBytesFlipPadded()
     {
         $parser = new Parser();
-        $parser->writeBytes(4, Buffer::hex('34'), true);
+        $parser->appendBuffer(Buffer::hex('34', 4), true);
         $this->assertEquals("34000000", $parser->getBuffer()->getHex());
     }
 
     public function testReadBytes()
     {
-        $bytes = '41424344';
+        $bytes = Buffer::hex('41424344');
 
         $parser = new Parser($bytes);
         $read = $parser->readBytes(4);
         $this->assertInstanceOf(Buffer::class, $read);
 
-        $hex = $read->getHex();
-        $this->assertSame($bytes, $hex);
+        $this->assertTrue($read->equals($bytes));
     }
 
     public function testReadBytesFlip()
     {
-        $bytes = '41424344';
+        $bytes = Buffer::hex('41424344');
 
         $parser = new Parser($bytes);
         $read = $parser->readBytes(4, true);
         $this->assertInstanceOf(Buffer::class, $read);
 
-        $hex = $read->getHex();
-        $this->assertSame('44434241', $hex);
+        $this->assertEquals($bytes->flip()->getHex(), $read->getHex());
     }
 
     /**
@@ -103,8 +114,7 @@ public function testReadBytesEmpty()
         // and length is zero.
 
         $parser = new Parser();
-        $data = $parser->readBytes(0);
-        $this->assertFalse(!!$data);
+        $parser->readBytes(0);
     }
     /**
      * @expectedException \BitWasp\Buffertools\Exceptions\ParserOutOfRange
@@ -112,7 +122,7 @@ public function testReadBytesEmpty()
      */
     public function testReadBytesEndOfString()
     {
-        $parser = new Parser('4041414142414141');
+        $parser = new Parser(Buffer::hex('4041414142414141'));
         $bytes1 = $parser->readBytes(4);
         $bytes2 = $parser->readBytes(4);
         $this->assertSame($bytes1->getHex(), '40414141');
@@ -125,7 +135,7 @@ public function testReadBytesEndOfString()
      */
     public function testReadBytesBeyondLength()
     {
-        $bytes = '41424344';
+        $bytes = Buffer::hex('41424344');
         $parser = new Parser($bytes);
         $parser->readBytes(5);
     }
diff --git a/tests/TemplateTest.php b/tests/TemplateTest.php
index 84f8c19..f42b409 100644
--- a/tests/TemplateTest.php
+++ b/tests/TemplateTest.php
@@ -29,7 +29,7 @@ public function testTemplate()
     public function testTemplateEmptyParse()
     {
         $template = new Template();
-        $parser = new Parser('010203040a0b0c0d');
+        $parser = new Parser(Buffer::hex('010203040a0b0c0d'));
         $template->parse($parser);
     }
 
diff --git a/tests/Types/IntegerBitSizeTest.php b/tests/Types/IntegerBitSizeTest.php
new file mode 100644
index 0000000..b1e8b7f
--- /dev/null
+++ b/tests/Types/IntegerBitSizeTest.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace BitWasp\Buffertools\Tests\Types;
+
+use BitWasp\Buffertools\Tests\BinaryTest;
+use BitWasp\Buffertools\Types\Int128;
+use BitWasp\Buffertools\Types\Int16;
+use BitWasp\Buffertools\Types\Int256;
+use BitWasp\Buffertools\Types\Int32;
+use BitWasp\Buffertools\Types\Int64;
+use BitWasp\Buffertools\Types\Int8;
+use BitWasp\Buffertools\Types\SignedIntInterface;
+use BitWasp\Buffertools\Types\Uint128;
+use BitWasp\Buffertools\Types\Uint16;
+use BitWasp\Buffertools\Types\Uint256;
+use BitWasp\Buffertools\Types\Uint32;
+use BitWasp\Buffertools\Types\Uint64;
+use BitWasp\Buffertools\Types\Uint8;
+use BitWasp\Buffertools\Types\UintInterface;
+
+class IntegerBitSizeTest extends BinaryTest
+{
+    public function getClassAndBitSize()
+    {
+        return [
+            [Uint8::class,8],
+            [Uint16::class,16],
+            [Uint32::class,32],
+            [Uint64::class,64],
+            [Uint128::class,128],
+            [Uint256::class,256],
+            [Int8::class,8],
+            [Int16::class,16],
+            [Int32::class,32],
+            [Int64::class,64],
+            [Int128::class,128],
+            [Int256::class,256],
+        ];
+    }
+
+    /**
+     * @dataProvider getClassAndBitSize
+     * @param string $integerClass
+     * @param int $bitSize
+     */
+    public function testBitSize(string $integerClass, int $bitSize)
+    {
+        /** @var UintInterface|SignedIntInterface $integer */
+        $integer = new $integerClass();
+        $this->assertEquals($bitSize, $integer->getBitSize());
+    }
+}