diff --git a/CHANGELOG b/CHANGELOG
index cac36e0..93e96f8 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,10 @@
+Version 0.6.0 (2019-12-18)
+==========================
+
+New features:
+- Added $allowSurrogates parameter to Encoding constructor
+- Added posErr public instance property to Encoding
+
 Version 0.5.0 (2019-12-13)
 ==========================
 
diff --git a/lib/Encoding/Big5.php b/lib/Encoding/Big5.php
index 6e84c96..3305a8d 100644
--- a/lib/Encoding/Big5.php
+++ b/lib/Encoding/Big5.php
@@ -24,12 +24,6 @@ class Big5 implements StatelessEncoding {
     protected $bufferedCode = 0;
 
 
-    /** Decodes the next character from the string and returns its code point number
-     *
-     * If the end of the string has been reached, false is returned
-     *
-     * @return int|bool
-     */
     public function nextCode() {
         $this->posChar++;
         if ($this->bufferedCode > 0) {
@@ -70,8 +64,10 @@ class Big5 implements StatelessEncoding {
                     return $code;
                 } else {
                     if ($b < 0x80) {
+                        $this->posErr = $this->posChar;
                         return self::err($this->errMode, [$this->posChar -1, --$this->posByte - 1]);
                     } else {
+                        $this->posErr = $this->posChar;
                         return self::err($this->errMode, [$this->posChar -1, $this->posByte - 2]);
                     }
                 }
@@ -85,16 +81,11 @@ class Big5 implements StatelessEncoding {
         } else {
             // dirty EOF
             $this->dirtyEOF = 1;
+            $this->posErr = $this->posChar;
             return self::err($this->errMode, [$this->posChar - 1, $this->posByte - $this->dirtyEOF]);
         }
     }
 
-    /** Returns the encoding of $codePoint as a byte string
-     *
-     * If $codePoint is less than 0 or greater than 1114111, an exception is thrown
-     *
-     * If $fatal is true, an exception will be thrown if the code point cannot be encoded into a character; otherwise HTML character references will be substituted
-     */
     public static function encode(int $codePoint, bool $fatal = true): string {
         if ($codePoint < 0 || $codePoint > 0x10FFFF) {
             throw new EncoderException("Encountered code point outside Unicode range ($codePoint)", self::E_INVALID_CODE_POINT);
diff --git a/lib/Encoding/EUCKR.php b/lib/Encoding/EUCKR.php
index 54ce73f..a3ce004 100644
--- a/lib/Encoding/EUCKR.php
+++ b/lib/Encoding/EUCKR.php
@@ -27,12 +27,6 @@ class EUCKR implements StatelessEncoding {
     protected $dirtyEOF = 0;
 
 
-    /** Decodes the next character from the string and returns its code point number
-     *
-     * If the end of the string has been reached, false is returned
-     *
-     * @return int|bool
-     */
     public function nextCode() {
         $this->posChar++;
         $lead = 0x00;
@@ -42,6 +36,7 @@ class EUCKR implements StatelessEncoding {
                 if ($b < 0x80) {
                     return $b;
                 } elseif ($b == 0x80 || $b == 0xFF) {
+                    $this->posErr = $this->posChar;
                     return self::err($this->errMode, [$this->posChar -1, $this->posByte - 1]);
                 } else {
                     $lead = $b;
@@ -57,8 +52,10 @@ class EUCKR implements StatelessEncoding {
                     return $code;
                 } else {
                     if ($b < 0x80) {
+                        $this->posErr = $this->posChar;
                         return self::err($this->errMode, [$this->posChar -1, --$this->posByte - 1]);
                     } else {
+                        $this->posErr = $this->posChar;
                         return self::err($this->errMode, [$this->posChar -1, $this->posByte - 2]);
                     }
                 }
@@ -72,16 +69,11 @@ class EUCKR implements StatelessEncoding {
         } else {
             // dirty EOF
             $this->dirtyEOF = 1;
+            $this->posErr = $this->posChar;
             return self::err($this->errMode, [$this->posChar - 1, $this->posByte - $this->dirtyEOF]);
         }
     }
 
-    /** Returns the encoding of $codePoint as a byte string
-     *
-     * If $codePoint is less than 0 or greater than 1114111, an exception is thrown
-     *
-     * If $fatal is true, an exception will be thrown if the code point cannot be encoded into a character; otherwise HTML character references will be substituted
-     */
     public static function encode(int $codePoint, bool $fatal = true): string {
         if ($codePoint < 0 || $codePoint > 0x10FFFF) {
             throw new EncoderException("Encountered code point outside Unicode range ($codePoint)", self::E_INVALID_CODE_POINT);
diff --git a/lib/Encoding/Encoding.php b/lib/Encoding/Encoding.php
index 5b7a731..04d4f58 100644
--- a/lib/Encoding/Encoding.php
+++ b/lib/Encoding/Encoding.php
@@ -19,10 +19,10 @@ interface Encoding {
     const E_UNAVAILABLE_CODE_POINT = 4;
 
     /** Constructs a new decoder
-     *
-     * If $fatal is true, an exception will be thrown whenever an invalid code sequence is encountered; otherwise replacement characters will be substituted
+     * @param bool $fatal If true, throw enceptions when encountering invalid input. If false, substitute U+FFFD REPLACEMENT CHARACTER instead
+     * @param bool $allowSurrogates If true, treats surrogate characters as valid input; this only affects UTF-8 and UTF-16 encodings
      */
-    public function __construct(string $string, bool $fatal = false);
+    public function __construct(string $string, bool $fatal = false, bool $allowSurrogates = false);
 
     /** Returns the current byte position of the decoder */
     public function posByte(): int;
@@ -40,15 +40,15 @@ interface Encoding {
      *
      * If the end of the string has been reached, false is returned
      *
-     * @return int|bool
+     * @return int|false
      */
     public function nextCode();
 
     /** Advance $distance characters through the string
-     *
-     * If $distance is negative, the operation will be performed in reverse
      *
      * If the end (or beginning) of the string was reached before the end of the operation, the remaining number of requested characters is returned
+     * 
+     * @param int $distance The number of characters to advance. If negative, the operation will seek back toward the beginning of the string
      */
     public function seek(int $distance): int;
 
@@ -58,10 +58,16 @@ interface Encoding {
     */
     public function rewind();
 
-    /** Retrieves the next $num characters (in UTF-8 encoding) from the string without advancing the character pointer */
+    /** Retrieves the next $num characters (in UTF-8 encoding) from the string without advancing the character pointer
+     * 
+     * @param int $num The number of characters to retrieve
+     */
     public function peekChar(int $num = 1): string;
 
-    /** Retrieves the next $num code points from the string, without advancing the character pointer */
+    /** Retrieves the next $num code points from the string, without advancing the character pointer
+     * 
+     * @param int $num The number of code points to retrieve
+     */
     public function peekCode(int $num = 1): array;
 
     /** Calculates the length of the string in bytes */
diff --git a/lib/Encoding/GBCommon.php b/lib/Encoding/GBCommon.php
index 6689a22..7c47b46 100644
--- a/lib/Encoding/GBCommon.php
+++ b/lib/Encoding/GBCommon.php
@@ -15,12 +15,6 @@ abstract class GBCommon implements StatelessEncoding {
 
     protected $dirtyEOF = 0;
 
-    /** Decodes the next character from the string and returns its code point number
-     *
-     * If the end of the string has been reached, false is returned
-     *
-     * @return int|bool
-     */
     public function nextCode() {
         $first = 0;
         $second = 0;
@@ -37,6 +31,7 @@ abstract class GBCommon implements StatelessEncoding {
                     $first = $b;
                     continue;
                 } else {
+                    $this->posErr = $this->posChar;
                     return self::err($this->errMode, [$this->posChar - 1, $this->posByte - 1]);
                 }
             } elseif ($second === 0) {
@@ -49,8 +44,10 @@ abstract class GBCommon implements StatelessEncoding {
                         $pointer = ($first - 0x81) * 190 + ($b - $offset);
                         return self::TABLE_GBK[$pointer];
                     } elseif ($b < 0x80) {
+                        $this->posErr = $this->posChar;
                         return self::err($this->errMode, [$this->posChar - 1, --$this->posByte]);
                     } else {
+                        $this->posErr = $this->posChar;
                         return self::err($this->errMode, [$this->posChar - 1, $this->posByte - 1]);
                     }
                 }
@@ -60,6 +57,7 @@ abstract class GBCommon implements StatelessEncoding {
                     continue;
                 } else {
                     $this->posByte -= 2;
+                    $this->posErr = $this->posChar;
                     return self::err($this->errMode, [$this->posChar - 1, $this->posByte - 1]);
                 }
             } else {
@@ -79,10 +77,12 @@ abstract class GBCommon implements StatelessEncoding {
                     if (isset($codePointOffset)) {
                         return $codePointOffset + $pointer - $offset;
                     } else {
+                        $this->posErr = $this->posChar;
                         return self::err($this->errMode, [$this->posChar - 1, $this->posByte - 1]);
                     }
                 } else {
                     $this->posByte -= 3;
+                    $this->posErr = $this->posChar;
                     return self::err($this->errMode, [$this->posChar - 1, $this->posByte - 1]);
                 }
             }
@@ -95,16 +95,11 @@ abstract class GBCommon implements StatelessEncoding {
         } else {
             // dirty EOF; note how many bytes the last character had
             $this->dirtyEOF = ($third ? 3 : ($second ? 2 : 1));
+            $this->posErr = $this->posChar;
             return self::err($this->errMode, [$this->posChar - 1, $this->posByte - $this->dirtyEOF]);
         }
     }
 
-    /** Returns the encoding of $codePoint as a byte string
-     *
-     * If $codePoint is less than 0 or greater than 1114111, an exception is thrown
-     *
-     * If $fatal is true, an exception will be thrown if the code point cannot be encoded into a character; otherwise HTML character references will be substituted
-     */
     public static function encode(int $codePoint, bool $fatal = true): string {
         if ($codePoint < 0 || $codePoint > 0x10FFFF) {
             throw new EncoderException("Encountered code point outside Unicode range ($codePoint)", self::E_INVALID_CODE_POINT);
diff --git a/lib/Encoding/GenericEncoding.php b/lib/Encoding/GenericEncoding.php
index 8b26626..9d0b2a0 100644
--- a/lib/Encoding/GenericEncoding.php
+++ b/lib/Encoding/GenericEncoding.php
@@ -13,40 +13,30 @@ trait GenericEncoding {
     protected $lenByte = null;
     protected $lenChar = null;
     protected $errMode = self::MODE_REPLACE;
+    protected $allowSurrogates = false;
 
-    /** Constructs a new decoder
-     *
-     * If $fatal is true, an exception will be thrown whenever an invalid code sequence is encountered; otherwise replacement characters will be substituted
-     */
-    public function __construct(string $string, bool $fatal = false) {
+    public $posErr = 0;
+
+    public function __construct(string $string, bool $fatal = false, bool $allowSurrogates = false) {
         $this->string = $string;
         $this->lenByte = strlen($string);
         $this->errMode = $fatal ? self::MODE_FATAL_DEC : self::MODE_REPLACE;
+        $this->allowSurrogates = $allowSurrogates;
     }
 
-    /** Returns the current byte position of the decoder */
     public function posByte(): int {
         return $this->posByte;
     }
 
-    /** Returns the current character position of the decoder */
     public function posChar(): int {
         return $this->posChar;
     }
 
-    /** Seeks to the start of the string
-     *
-     * This is usually faster than using the seek method for the same purpose
-    */
     public function rewind() {
         $this->posByte = 0;
         $this->posChar = 0;
     }
 
-    /** Retrieve the next character in the string, in UTF-8 encoding
-     *
-     * The returned character may be a replacement character, or the empty string if the end of the string has been reached
-     */
     public function nextChar(): string {
         // get the byte at the current position
         $b = @$this->string[$this->posByte];
@@ -64,12 +54,6 @@ trait GenericEncoding {
         }
     }
 
-    /** Advance $distance characters through the string
-     *
-     * If $distance is negative, the operation will be performed in reverse
-     *
-     * If the end (or beginning) of the string was reached before the end of the operation, the remaining number of requested characters is returned
-     */
     public function seek(int $distance): int {
         if ($distance > 0) {
             if ($this->posByte == strlen($this->string)) {
@@ -94,7 +78,6 @@ trait GenericEncoding {
         }
     }
 
-    /** Retrieves the next $num characters (in UTF-8 encoding) from the string without advancing the character pointer */
     public function peekChar(int $num = 1): string {
         $out = "";
         $state = $this->stateSave();
@@ -108,7 +91,6 @@ trait GenericEncoding {
         return $out;
     }
 
-    /** Retrieves the next $num code points from the string, without advancing the character pointer */
     public function peekCode(int $num = 1): array {
         $out = [];
         $state = $this->stateSave();
@@ -122,15 +104,10 @@ trait GenericEncoding {
         return $out;
     }
 
-    /** Calculates the length of the string in bytes */
     public function lenByte(): int {
         return $this->lenByte;
     }
 
-    /** Calculates the length of the string in code points
-     *
-     * Note that this may involve processing to the end of the string
-    */
     public function lenChar(): int {
         return $this->lenChar ?? (function() {
             $state = $this->stateSave();
@@ -141,19 +118,16 @@ trait GenericEncoding {
         })();
     }
 
-    /** Returns whether the character pointer is at the end of the string */
     public function eof(): bool {
         return $this->posByte >= $this->lenByte;
     }
 
-    /** Generates an iterator which steps through each character in the string */
     public function chars(): \Generator {
         while (($c = $this->nextChar()) !== "") {
             yield ($this->posChar - 1) => $c;
         }
     }
 
-    /** Generates an iterator which steps through each code point in the string  */
     public function codes(): \Generator {
         while (($c = $this->nextCode()) !== false) {
             yield ($this->posChar - 1) => $c;
@@ -165,6 +139,7 @@ trait GenericEncoding {
         return [
             'posChar' => $this->posChar,
             'posByte' => $this->posByte,
+            'posErr'  => $this->posErr,
         ];
     }
 
@@ -191,7 +166,7 @@ trait GenericEncoding {
                 // fatal replacement mode for decoders
                 throw new DecoderException("Invalid code sequence at character offset {$data[0]} (byte offset {$data[1]})", self::E_INVALID_BYTE);
             case self::MODE_FATAL_ENC:
-                // fatal replacement mode for decoders; not applicable to Unicode transformation formats
+                // fatal replacement mode for encoders; not applicable to Unicode transformation formats
                 throw new EncoderException("Code point $data not available in target encoding", self::E_UNAVAILABLE_CODE_POINT);
             default:
                 // indicative of internal bug; should never be triggered
diff --git a/lib/Encoding/SingleByteEncoding.php b/lib/Encoding/SingleByteEncoding.php
index 9bdf996..0b48684 100644
--- a/lib/Encoding/SingleByteEncoding.php
+++ b/lib/Encoding/SingleByteEncoding.php
@@ -9,10 +9,6 @@ namespace MensBeam\Intl\Encoding;
 abstract class SingleByteEncoding implements StatelessEncoding {
     use GenericEncoding;
 
-    /** Retrieve the next character in the string, in UTF-8 encoding
-     *
-     * The returned character may be a replacement character, or the empty string if the end of the string has been reached
-     */
     public function nextChar(): string {
         // get the byte at the current position
         $b = @$this->string[$this->posChar];
@@ -29,12 +25,6 @@ abstract class SingleByteEncoding implements StatelessEncoding {
         }
     }
 
-    /** Decodes the next character from the string and returns its code point number
-     *
-     * If the end of the string has been reached, false is returned
-     *
-     * @return int|bool
-     */
     public function nextCode() {
         // get the byte at the current position
         $b = @$this->string[$this->posChar];
@@ -51,12 +41,6 @@ abstract class SingleByteEncoding implements StatelessEncoding {
         }
     }
 
-    /** Returns the encoding of $codePoint as a byte string
-     *
-     * If $codePoint is less than 0 or greater than 1114111, an exception is thrown
-     *
-     * If $fatal is true, an exception will be thrown if the code point cannot be encoded into a character; otherwise HTML character references will be substituted
-     */
     public static function encode(int $codePoint, bool $fatal = true): string {
         if ($codePoint < 0 || $codePoint > 0x10FFFF) {
             throw new EncoderException("Encountered code point outside Unicode range ($codePoint)", self::E_INVALID_CODE_POINT);
@@ -67,12 +51,6 @@ abstract class SingleByteEncoding implements StatelessEncoding {
         }
     }
 
-    /** Advance $distance characters through the string
-     *
-     * If $distance is negative, the operation will be performed in reverse
-     *
-     * If the end (or beginning) of the string was reached before the end of the operation, the remaining number of requested characters is returned
-     */
     public function seek(int $distance): int {
         if ($distance > 0) {
             while ($this->posChar < $this->lenByte && $distance > 0) {
@@ -92,20 +70,14 @@ abstract class SingleByteEncoding implements StatelessEncoding {
         }
     }
 
-    /** Returns the current byte position of the decoder */
     public function posByte(): int {
         return $this->posChar;
     }
 
-    /** Calculates the length of the string in code points
-     *
-     * Note that this may involve processing to the end of the string
-    */
     public function lenChar(): int {
         return $this->lenByte;
     }
 
-    /** Returns whether the character pointer is at the end of the string */
     public function eof(): bool {
         return $this->posChar >= $this->lenByte;
     }
diff --git a/lib/Encoding/UTF16.php b/lib/Encoding/UTF16.php
index 0bce6d9..8a8f752 100644
--- a/lib/Encoding/UTF16.php
+++ b/lib/Encoding/UTF16.php
@@ -11,12 +11,6 @@ abstract class UTF16 implements Encoding {
     
     protected $dirtyEOF = 0;
 
-    /** Decodes the next character from the string and returns its code point number
-     *
-     * If the end of the string has been reached, false is returned
-     *
-     * @return int|bool
-     */
     public function nextCode() {
         $lead_b = null;
         $lead_s = null;
@@ -36,6 +30,9 @@ abstract class UTF16 implements Encoding {
                 if (!is_null($lead_s)) {
                     if ($code >= 0xDC00 && $code <= 0xDFFF) {
                         return 0x10000 + (($lead_s - 0xD800) << 10) + ($code - 0xDC00);
+                    } elseif ($this->allowSurrogates) {
+                        $this->posByte -= 2;
+                        return $lead_s;
                     } else {
                         $this->posByte -= 2;
                         return self::err($this->errMode, [$this->posChar - 1, $this->posByte - 2]);
@@ -45,7 +42,11 @@ abstract class UTF16 implements Encoding {
                         $lead_s = $code;
                         continue;
                     } elseif ($code >= 0xDC00 && $code <= 0xDFFF) {
-                        return self::err($this->errMode, [$this->posChar - 1, $this->posByte - 2]);
+                        if ($this->allowSurrogates) {
+                            return $code;
+                        } else {
+                            return self::err($this->errMode, [$this->posChar - 1, $this->posByte - 2]);
+                        }
                     } else {
                         return $code;
                     }
@@ -65,10 +66,6 @@ abstract class UTF16 implements Encoding {
         }
     }
 
-    /** Retrieve the next character in the string, in UTF-8 encoding
-     *
-     * The returned character may be a replacement character, or the empty string if the end of the string has been reached
-     */
     public function nextChar(): string {
         // get the byte at the current position
         $b = @$this->string[$this->posByte];
diff --git a/lib/Encoding/UTF8.php b/lib/Encoding/UTF8.php
index 69d500c..ea39156 100644
--- a/lib/Encoding/UTF8.php
+++ b/lib/Encoding/UTF8.php
@@ -12,12 +12,6 @@ class UTF8 implements StatelessEncoding {
     const NAME = "UTF-8";
     const LABELS = ["unicode-1-1-utf-8", "utf-8", "utf8"];
 
-    /** Decodes the next character from the string and returns its code point number
-     *
-     * If the end of the string has been reached, false is returned
-     *
-     * @return int|bool
-     */
     public function nextCode() {
         // this function effectively implements https://encoding.spec.whatwg.org/#utf-8-decoder
         // optimization for ASCII characters
@@ -46,7 +40,7 @@ class UTF8 implements StatelessEncoding {
                     if ($b==0xE0) {
                         $lower = 0xA0;
                     } elseif ($b==0xED) {
-                        $upper = 0x9F;
+                        $upper = ($this->allowSurrogates) ? 0xBF : 0x9F;
                     }
                     $point = $b & 0xF;
                 } elseif ($b >= 0xF0 && $b <= 0xF4) { // four-byte character
@@ -58,9 +52,11 @@ class UTF8 implements StatelessEncoding {
                     }
                     $point = $b & 0x7;
                 } else { // invalid byte
+                    $this->posErr = $this->posChar;
                     return self::err($this->errMode, [$this->posChar, $this->posByte]);
                 }
             } elseif ($b < $lower || $b > $upper) {
+                $this->posErr = $this->posChar;
                 return self::err($this->errMode, [$this->posChar, $this->posByte--]);
             } else {
                 $lower = 0x80;
@@ -72,12 +68,6 @@ class UTF8 implements StatelessEncoding {
         return $point;
     }
 
-    /** Returns the encoding of $codePoint as a byte string
-     *
-     * If $codePoint is less than 0 or greater than 1114111, an exception is thrown
-     *
-     * If $fatal is true, an exception will be thrown if the code point cannot be encoded into a character; otherwise HTML character references will be substituted. When encoding to UTF-8, all Unicode characters can be encoded, so the argument is ignored
-     */
     public static function encode(int $codePoint, bool $fatal = true): string {
         // this function implements https://encoding.spec.whatwg.org/#utf-8-encoder
         if ($codePoint < 0 || $codePoint > 0x10FFFF) {
diff --git a/tests/cases/Encoding/TestBig5.php b/tests/cases/Encoding/TestBig5.php
index 85711de..f86568e 100644
--- a/tests/cases/Encoding/TestBig5.php
+++ b/tests/cases/Encoding/TestBig5.php
@@ -128,6 +128,14 @@ class TestBig5 extends \MensBeam\Intl\Test\CoderDecoderTest {
         return parent::testIterateThroughAString($input, $exp);
     }
 
+    /**
+     * @dataProvider provideStrings
+     * @coversNothing
+    */
+    public function testIterateThroughAStringAllowingSurrogates(string $input, array $strictExp, array $relaxedExp = null) {
+        return parent::testIterateThroughAStringAllowingSurrogates($input, $strictExp, $relaxedExp);
+    }
+
     public function provideCodePoints() {
         return [
             'U+0064 (HTML)'    => [false, 0x64, "64"],
diff --git a/tests/cases/Encoding/TestEUCKR.php b/tests/cases/Encoding/TestEUCKR.php
index 6fc35a7..eec110f 100644
--- a/tests/cases/Encoding/TestEUCKR.php
+++ b/tests/cases/Encoding/TestEUCKR.php
@@ -128,6 +128,14 @@ class TestEUCKR extends \MensBeam\Intl\Test\CoderDecoderTest {
         return parent::testIterateThroughAString($input, $exp);
     }
 
+    /**
+     * @dataProvider provideStrings
+     * @coversNothing
+    */
+    public function testIterateThroughAStringAllowingSurrogates(string $input, array $strictExp, array $relaxedExp = null) {
+        return parent::testIterateThroughAStringAllowingSurrogates($input, $strictExp, $relaxedExp);
+    }
+
     public function provideCodePoints() {
         return [
             'U+0064 (HTML)'    => [false, 0x64, "64"],
diff --git a/tests/cases/Encoding/TestGB18030.php b/tests/cases/Encoding/TestGB18030.php
index 293b1d7..419d21f 100644
--- a/tests/cases/Encoding/TestGB18030.php
+++ b/tests/cases/Encoding/TestGB18030.php
@@ -136,6 +136,14 @@ class TestGB18030 extends \MensBeam\Intl\Test\CoderDecoderTest {
         return parent::testIterateThroughAString($input, $exp);
     }
 
+    /**
+     * @dataProvider provideStrings
+     * @coversNothing
+    */
+    public function testIterateThroughAStringAllowingSurrogates(string $input, array $strictExp, array $relaxedExp = null) {
+        return parent::testIterateThroughAStringAllowingSurrogates($input, $strictExp, $relaxedExp);
+    }
+
     public function provideCodePoints() {
         // bytes confirmed using Firefox
         $series_gb18030 = [
diff --git a/tests/cases/Encoding/TestSingleByte.php b/tests/cases/Encoding/TestSingleByte.php
index 7fa81b3..f1fd634 100644
--- a/tests/cases/Encoding/TestSingleByte.php
+++ b/tests/cases/Encoding/TestSingleByte.php
@@ -205,6 +205,15 @@ class TestSingleByte extends \MensBeam\Intl\Test\CoderDecoderTest {
         return parent::testIterateThroughAString($input, $exp);
     }
 
+    /**
+     * @dataProvider provideStrings
+     * @coversNothing
+    */
+    public function testIterateThroughAStringAllowingSurrogates(string $input, array $exp, $class = null) {
+        $this->testedClass = $class;
+        return parent::testIterateThroughAStringAllowingSurrogates($input, $exp, $exp);
+    }
+
     public function provideClasses() {
         foreach (self::$classes as $name => $class) {
             yield $name => [$class];
diff --git a/tests/cases/Encoding/TestUTF16BE.php b/tests/cases/Encoding/TestUTF16BE.php
index 2e88e53..c77ab04 100644
--- a/tests/cases/Encoding/TestUTF16BE.php
+++ b/tests/cases/Encoding/TestUTF16BE.php
@@ -6,7 +6,6 @@
 declare(strict_types=1);
 namespace MensBeam\Intl\TestCase\Encoding;
 
-use MensBeam\Intl\Encoding\UTF16LE;
 use MensBeam\Intl\Encoding\UTF16BE;
 
 class TestUTF16BE extends TestUTF16LE {
@@ -30,7 +29,10 @@ class TestUTF16BE extends TestUTF16LE {
 
     public function provideStrings() {
         foreach (parent::provideStrings() as $name => $test) {
-            list($string, $codes) = $test;
+            if (sizeof($test) == 2) {
+                $test[] = null;
+            }
+            list($string, $codes, $altCodes) = $test;
             $words = explode(" ", $string);
             foreach ($words as $a => $word) {
                 if (strlen($word) == 4) {
@@ -38,7 +40,7 @@ class TestUTF16BE extends TestUTF16LE {
                 }
             }
             $string = implode(" ", $words);
-            yield $name => [$string, $codes];
+            yield $name => [$string, $codes, $altCodes];
         }
     }
 }
diff --git a/tests/cases/Encoding/TestUTF16LE.php b/tests/cases/Encoding/TestUTF16LE.php
index 1424b44..2129df3 100644
--- a/tests/cases/Encoding/TestUTF16LE.php
+++ b/tests/cases/Encoding/TestUTF16LE.php
@@ -7,7 +7,6 @@ declare(strict_types=1);
 namespace MensBeam\Intl\TestCase\Encoding;
 
 use MensBeam\Intl\Encoding\UTF16LE;
-use MensBeam\Intl\Encoding\UTF16BE;
 
 class TestUTF16LE extends \MensBeam\Intl\Test\DecoderTest {
     protected $testedClass = UTF16LE::class;
@@ -119,6 +118,14 @@ class TestUTF16LE extends \MensBeam\Intl\Test\DecoderTest {
         return parent::testIterateThroughAString($input, $exp);
     }
 
+    /**
+     * @dataProvider provideStrings
+     * @covers MensBeam\Intl\Encoding\UTF16::nextCode
+    */
+    public function testIterateThroughAStringAllowingSurrogates(string $input, array $strictExp, array $relaxedExp = null) {
+        return parent::testIterateThroughAStringAllowingSurrogates($input, $strictExp, $relaxedExp);
+    }
+
     public function provideStrings() {
         return [
             // control samples
@@ -130,10 +137,10 @@ class TestUTF16LE extends \MensBeam\Intl\Test\DecoderTest {
             'EOF after lead surrogate' => ["0000 34D8", [0, 65533]],
             'EOF in trail surrogate' => ["0000 34D8 1E", [0, 65533]],
             // invalid UTF-16 surrogates
-            'lead surrogate without trail' => ["34D8 0000", [65533, 0]],
-            'trail surrogate without lead' => ["1EDD 0000", [65533, 0]],
-            'double lead surrogate' => ["34D8 34D8 1EDD", [65533, 119070]],
-            'double trail surrogate' => ["34D8 1EDD 1EDD", [119070, 65533]],
+            'lead surrogate without trail' => ["34D8 0000", [65533, 0], [0xD834, 0]],
+            'trail surrogate without lead' => ["1EDD 0000", [65533, 0], [0xDD1E, 0]],
+            'double lead surrogate' => ["34D8 34D8 1EDD", [65533, 119070], [0xD834, 119070]],
+            'double trail surrogate' => ["34D8 1EDD 1EDD", [119070, 65533], [119070, 0xDD1E]],
         ];
     }
 }
diff --git a/tests/cases/Encoding/TestUTF8.php b/tests/cases/Encoding/TestUTF8.php
index 6be0395..8c027ed 100644
--- a/tests/cases/Encoding/TestUTF8.php
+++ b/tests/cases/Encoding/TestUTF8.php
@@ -128,6 +128,14 @@ class TestUTF8 extends \MensBeam\Intl\Test\CoderDecoderTest {
         return parent::testIterateThroughAString($input, $exp);
     }
 
+    /**
+     * @dataProvider provideStrings
+     * @covers MensBeam\Intl\Encoding\UTF8::nextCode
+    */
+    public function testIterateThroughAStringAllowingSurrogates(string $input, array $strictExp, array $relaxedExp = null) {
+        return parent::testIterateThroughAStringAllowingSurrogates($input, $strictExp, $relaxedExp);
+    }
+
     public function provideCodePoints() {
         return [
             'U+007A (HTML)'    => [false, 0x7A, "7A"],
@@ -190,9 +198,10 @@ class TestUTF8 extends \MensBeam\Intl\Test\CoderDecoderTest {
             'overlong U+10FFFF - 5 bytes' => ["F8 84 8F BF BF", [65533, 65533, 65533, 65533, 65533]],
             'overlong U+10FFFF - 6 bytes' => ["FC 80 84 8F BF BF", [65533, 65533, 65533, 65533, 65533, 65533]],
             // UTF-16 surrogates
-            'lead surrogate' => ["ED A0 80", [65533, 65533, 65533]],
-            'trail surrogate' => ["ED B0 80", [65533, 65533, 65533]],
-            'surrogate pair' => ["ED A0 80 ED B0 80", [65533, 65533, 65533, 65533, 65533, 65533]],
+            // surrogates have alternate outputs for when surrogates are being allowed
+            'lead surrogate' => ["ED A0 80", [65533, 65533, 65533], [0xD800]],
+            'trail surrogate' => ["ED B0 80", [65533, 65533, 65533], [0xDC00]],
+            'surrogate pair' => ["ED A0 80 ED B0 80", [65533, 65533, 65533, 65533, 65533, 65533], [0xD800, 0xDC00]],
             // self-sync edge cases
             'trailing continuation' => ["0A 80 80", [10, 65533, 65533]],
             'trailing continuation 2' => ["E5 8F A4 80", [21476, 65533]],
diff --git a/tests/cases/Encoding/TestXUserDefined.php b/tests/cases/Encoding/TestXUserDefined.php
index 5d47dda..decd5bc 100644
--- a/tests/cases/Encoding/TestXUserDefined.php
+++ b/tests/cases/Encoding/TestXUserDefined.php
@@ -109,6 +109,14 @@ class TestXUserDefined extends \MensBeam\Intl\Test\DecoderTest {
         return parent::testIterateThroughAString($input, $exp);
     }
 
+    /**
+     * @dataProvider provideStrings
+     * @coversNothing
+    */
+    public function testIterateThroughAStringAllowingSurrogates(string $input, array $strictExp, array $relaxedExp = null) {
+        return parent::testIterateThroughAStringAllowingSurrogates($input, $strictExp, $relaxedExp);
+    }
+
     public function provideStrings() {
         $a_bytes = [];
         $a_codes = [];
diff --git a/tests/lib/DecoderTest.php b/tests/lib/DecoderTest.php
index 56dcfa1..4730420 100644
--- a/tests/lib/DecoderTest.php
+++ b/tests/lib/DecoderTest.php
@@ -281,10 +281,18 @@ abstract class DecoderTest extends \PHPUnit\Framework\TestCase {
     }
 
     public function testIterateThroughAString(string $input, array $exp) {
+        $this->iterateThroughAString($input, $exp, false);
+    }
+
+    public function testIterateThroughAStringAllowingSurrogates(string $input, array $strictExp, array $relaxedExp = null) {
+        $exp = $relaxedExp ?? $strictExp;
+        $this->iterateThroughAString($input, $exp, true);
+    }
+
+    protected function iterateThroughAString(string $input, array $exp, bool $allowSurrogates) {
         $class = $this->testedClass;
         $input = $this->prepString($input);
-        $s = new $class($input);
-        $out = [];
+        $s = new $class($input, false, $allowSurrogates);
         $a = 0;
         $this->assertTrue(true); // prevent risky test of empty string
         foreach ($s->codes() as $index => $p) {