title	type	order
Mutators	guide	5

Infection supports a set of Mutators which are based on AST and PHP-Parser project.

Read more about how to execute only particular set of mutators using Name column

Function Signature

Name	Original	Mutated
PublicVisibility	`public function ...`	`protected function ...`
ProtectedVisibility	`protected function ...`	`private function ...`

To verify that the visibility of a method is necessary. If the visibility of a method can be reduced from public to protected or private, this may be an indication that the publicly accessible part of API of a class is larger than what’s strictly necessary. This mutator will drive the source code towards classes with smaller publicly accessible APIs and thus better encapsulation.

Unwrap Function

The Unwrap* mutator family will unwrap function parameters.

Name	Original	Mutated
UnwrapArrayChangeKeyCase	`$a = array_change_key_case(['foo' => 'bar']);`	`$a = ['foo' => 'bar'];`
UnwrapArrayChunk	`$a = array_chunk(['A', 'B', 'C'], 2);`	`$a = ['A', 'B', 'C'];`
UnwrapArrayColumn	`$a = array_column([['foo' => 'bar]], 'foo');`	`$a = [['foo' => 'bar]];`
UnwrapArrayCombine	`$a = array_combine(['A', 'B', 'C'], ['foo', 'bar', 'baz']);`	`$a = ['A', 'B', 'C'];`
UnwrapArrayDiff	`$a = array_diff(['A', 'B', 'C'], ['D']);`	`$a = ['A', 'B', 'C'];`
UnwrapArrayDiffAssoc	`$a = array_diff_assoc(['foo' => 'bar'], ['baz' => 'bar]);`	`$a = ['foo' => 'bar'];`
UnwrapArrayDiffKey	`$a = array_diff_key(['foo' => 'bar'], ['baz' => 'bar]);`	`$a = ['foo' => 'bar'];`
UnwrapArrayDiffUassoc	`$a = array_diff_assoc(['foo' => 'bar'], ['baz' => 'bar], $keyCompareFunc);`	`$a = ['foo' => 'bar'];`
UnwrapArrayDiffUkey	`$a = array_diff_ukey(['foo' => 'bar'], ['baz' => 'bar], $keyCompareFunc);`	`$a = ['foo' => 'bar'];`
UnwrapArrayFilter	`$a = array_filter(['A', 1, 'C'], 'is_int');`	`$a = ['A', 1, 'C'];`
UnwrapArrayFlip	`$a = array_flip(['A', 'B', 'C']);`	`$a = ['A', 'B', 'C'];`
UnwrapArrayIntersect	`$a = array_intersect(['A', 'B', 'C'], ['D']);`	`$a = ['A', 'B', 'C'];`
UnwrapArrayIntersectKey	`$a = array_intersect_key(['foo' => 'bar'], ['bar' => 'baz']);`	`$a = ['foo' => 'bar'];`
UnwrapArrayIntersectUassoc	`$a = array_intersect_uassoc(['foo' => 'bar'], ['bar' => 'baz'], $keyCompareFunc);`	`$a = ['foo' => 'bar'];`
UnwrapArrayIntersectUkey	`$a = array_intersect_ukey(['foo' => 'bar'], ['bar' => 'baz'], $keyCompareFunc);`	`$a = ['foo' => 'bar'];`
UnwrapArrayKeys	`$a = array_keys(['foo' => 'bar']);`	`$a = ['foo' => 'bar'];`
UnwrapArrayMap	`$a = array_map('strtolower', ['A', 'B', 'C']);`	`$a = ['A', 'B', 'C'];`
UnwrapArrayMerge	`$a = array_merge(['A', 'B', 'C'], ['D']);`	`$a = ['A', 'B', 'C'];`
UnwrapArrayMergeRecursive	`$a = array_merge_recursive(['A', 'B', 'C'], ['D']);`	`$a = ['A', 'B', 'C'];`
UnwrapArrayReduce	`$a = array_reduce(['A', 'B', 'C'], $callback, ['D']);`	`$a = ['D'];`
UnwrapArrayReplace	`$a = array_replace(['A', 'B', 'C'], ['D']);`	`$a = ['A', 'B', 'C'];`
UnwrapArrayReplaceRecursive	`$a = array_replace_recursive(['A', 'B', 'C'], ['D']);`	`$a = ['A', 'B', 'C'];`
UnwrapArrayReverse	`$a = array_reverse(['A', 'B', 'C']);`	`$a = ['A', 'B', 'C'];`
UnwrapArraySlice	`$a = array_slice(['A', 'B', 'C'], 1);`	`$a = ['A', 'B', 'C'];`
UnwrapArraySplice	`$a = array_splice(['A', 'B', 'C'], 1);`	`$a = ['A', 'B', 'C'];`
UnwrapArrayUdiff	`$a = array_udiff(['foo' => 'bar'], ['baz' => 'bar], $valueCompareFunc);`	`$a = ['foo' => 'bar'];`
UnwrapArrayUdiffAssoc	`$a = array_udiff_assoc(['foo' => 'bar'], ['baz' => 'bar], $valueCompareFunc);`	`$a = ['foo' => 'bar'];`
UnwrapArrayUdiffUassoc	`$a = array_udiff_uassoc(['foo' => 'bar'], ['baz' => 'bar], $valueCompareFunc, $keyCompareFunc);`	`$a = ['foo' => 'bar'];`
UnwrapArrayUintersect	`$a = array_uintersect(['foo' => 'bar'], ['baz' => 'bar], $valueCompareFunc);`	`$a = ['foo' => 'bar'];`
UnwrapArrayUintersectAssoc	`$a = array_uintersect_assoc(['foo' => 'bar'], ['baz' => 'bar], $valueCompareFunc);`	`$a = ['foo' => 'bar'];`
UnwrapArrayUintersectUassoc	`$a = array_uintersect_uassoc(['foo' => 'bar'], ['baz' => 'bar], $valueCompareFunc, $keyCompareFunc);`	`$a = ['foo' => 'bar'];`
UnwrapArrayUnique	`$a = array_unique(['foo', 'bar', 'bar']);`	`$a = ['foo', 'bar', 'bar'];`
UnwrapArrayValues	`$a = array_values(['foo' => 'bar']);`	`$a = ['foo' => 'bar'];`
UnwrapLcFirst	`$a = lcfirst('Hello, world!');`	`$a = 'Hello, world!';`
UnwrapStrRepeat	`$a = str_repeat('A', 3);`	`$a = 'A';`
UnwrapStrToLower	`$a = strtolower('Hello!');`	`$a = 'Hello!';`
UnwrapStrToUpper	`$a = strtoupper('Hello, world!');`	`$a = 'Hello, world!';`
UnwrapTrim	`$a = trim(' Hello, world! ');`	`$a = 'Hello, world!';`
UnwrapUcFirst	`$a = ucfirst('hello, world!');`	`$a = 'hello, world!';`
UnwrapUcWords	`$a = ucwords('hello, world!');`	`$a = 'hello, world!';`

Binary Arithmetic

Name	Original	Mutated
Plus	+	-
Minus	-	+
Multiplication	*	/
Division	/	*
Modulus	%	*
Exponentiation	**	/
MulEqual	*=	/=
PlusEqual	+=	-=
MinusEqual	-=	+=
DivEqual	/=	*=
ModEqual	%=	*=
PowEqual	**=	/=
BitwiseAnd	&	\|
BitwiseOr	\|	&
BitwiseXor	^	&
BitwiseNot	~
ShiftRight	>>	<<
ShiftLeft	<<	>>
AssignmentEqual	==	=
Assignment	+=	=
Assignment	-=	=
Assignment	*=	=
Assignment	**=	=
Assignment	/=	=
Assignment	%=	=
Assignment	.=	=
Assignment	&=	=
Assignment	\|=	=
Assignment	^=	=
Assignment	<<=	=
Assignment	>>=	=
Assignment Coalesce	??=	=

Round Family

The Round Family mutator will make sure that there's enough tests to cover the rounding possibilities.

Name	Original	Mutated
RoundingFamily	`round()`	`floor()`
RoundingFamily	`round()`	`ceil()`
RoundingFamily	`ceil()`	`floor()`
RoundingFamily	`ceil()`	`round()`
RoundingFamily	`floor()`	`round()`
RoundingFamily	`floor()`	`ceil()`

Boolean Substitution

Name	Original	Mutated
ArrayItem	`[$a->foo => $b->bar]`	`[$a->foo > $b->bar]`
TrueValue	true	false
FalseValue	false	true
LogicalAnd	&&	\|\|
LogicalOr	\|\|	&&
LogicalLowerAnd	and	or
LogicalLowerOr	or	and
LogicalNot	!
Yield_	`yield $a => $b;`	`yield $a > $b;`
Coalesce	`$a ?? $b`	`$b`

`TrueValue`

Default settings:

in_array: false: whether to mutate 3rd argument true in function call
array_search: false: whether to mutate 3rd argument true in function call

infection.json:

{
    "mutators": {
        "TrueValue": {
            "settings": {
                "in_array": true,
                "array_search": true
            }
        }
     }
}

Conditional Boundaries

Name	Original	Mutated
GreaterThan	>	>=
LessThan	<	<=
GreaterThanOrEqualTo	>=	>
LessThanOrEqualTo	<=	<

Equal or Identical Checks

Name	Original	Mutated
EqualIdentical	`==`	`===`
NotEqualNotIdentical	`!=`	`!==`
IdenticalEqual	`===`	`==`
NotIdenticalNotEqual	`!==`	`!=`

These mutators are disabled by default, you can use the @equal or @identical profiles to enable the ones you prefer.

Negated Conditionals

Name	Original	Mutated
Equal	==	!=
NotEqual	!=	==
Identical	===	!==
NotIdentical	!==	===
GreaterThanNegotiation	>	<=
LessThanNegotiation	<	>=
GreaterThanOrEqualToNegotiation	>=	<
LessThanOrEqualToNegotiation	<=	>

Increments

Name	Original	Mutated
Increment	++	--
Decrement	--	++

Return Values

Name	Original	Mutated
TrueValue	return true;	return false;
FalseValue	return false;	return true;
OneZeroInteger	return 0;	return 1;
IntegerNegation	return `(Any Integer)`;	return `-(Any Integer)`;
OneZeroFloat	return 0.0;	return 1.0;
OneZeroFloat	return 1.0;	return 0.0;
FloatNegation	return `(Any Float)`;	return `-(Any Float)`;
This	return $this;	return null;
FunctionCall	return function();	function(); return null;
NewObject	return new Class();	new Class(); return null;

Removal Mutators

Name	Original	Mutated
ArrayItemRemoval	`[1, $a, '3']`	`[$a, '3']` depending on configuration
FunctionCallRemoval	foo_bar($a)	-
MethodCallRemoval	$this->method($var)	-

`ArrayItemRemoval`

Configuration options:

remove: first: defines the way the mutator operates. Could be:
- first - remove only first element from each array
- last - remove only last element from each array
- all - remove every element one by one from each array resulting in as many mutations as total number of items in arrays.
limit: PHP_INT_MAX: when remove = all specifies maximum number of elements that will be removed form array. Only elements at the beginning will be mutated.

When using all option we advise to set the limit as well

You should remember to exclude files containing large arrays (like configuration) when using ArrayItemRemoval mutator in all mode

infection.json:

{
    "mutators": {
        "ArrayItemRemoval": {
            "settings": {
                "remove": "all",
                "limit": 15
            }
        }
     }
}

Loop

Name	Original	Mutated
Break_	break;	continue;
Continue_	continue;	break;
Foreach_	foreach ($someVar as ...);	foreach ([] as ...);
For_	for ($i=0; $i < 10; $i++);	for ($i=0; false; $i++);

Sorting

Name	Original	Mutated
Spaceship	$a <=> $b	$b <=> $a

Literal Numbers

Name	Original	Mutated
OneZeroInteger	0	1
OneZeroInteger	1	0
OneZeroFloat	0.0	1.0
OneZeroFloat	1.0	0.0
DecrementInteger	7	6
IncrementInteger	7	8

Exceptions

Name	Original	Mutated
Throw_	`throw new NotFoundException();`	`new NotFoundException();`
Finally_	`try {} catch (\Exception $e) {} finally {}`	`try {} catch (\Exception $e) {}`

Type Casting

Name	Original	Mutated
CastArray	`(array) $value;`	`$value`
CastBool	`(bool) $value;`	`$value`
CastFloat	`(float) $value;`	`$value`
CastInt	`(int) $value;`	`$value`
CastObject	`(object) $value;`	`$value`
CastString	`(string) $value;`	`$value`

Regex

Name	Original	Mutated
PregQuote	`$a = preg_quote('text');`	`$a = 'text';`
PregMatchMatches	`preg_match('/pattern/', $value, $matches);`	`(int) $matches = array();`

Extensions

Name	Original	Mutated
MBString	`mb_chr($code);`	`chr($code);`
	`mb_ord($character);`	`ord($character);`
	`mb_parse_str('text', $results);`	`parse_str('text', $results);`
	`mb_send_mail($to, $subject, $message, $headers, $parameters);`	`mail($to, $subject, $message, $headers, $parameters);`
	`mb_strcut('text', 0, 123, 'utf-8');`	`substr('text', 0, 123);`
	`mb_stripos('text', 't', 0, 'utf-8');`	`stripos('text', 't', 0);`
	`mb_stristr('text', 't', true, 'utf-8');`	`stristr('text', 't', true);`
	`mb_strlen('text', 'utf-8');`	`strlen('text');`
	`mb_strpos('text', 't', 0, 'utf-8');`	`strpos('text', 't', 0);`
	`mb_strrchr('text', 't', true, 'utf-8');`	`strrchr('text', 't', true);`
	`mb_strripos('text', 't', 0, 'utf-8');`	`strripos('text', 't', 0);`
	`mb_strrpos('text', 't', 0, 'utf-8');`	`strrpos('text', 't', 0);`
	`mb_strstr('text', 't', true, 'utf-8');`	`strstr('text', 't', true);`
	`mb_strtolower('text', 'utf-8');`	`strtolower('text');`
	`mb_strtoupper('text', 'utf-8');`	`strtoupper('text');`
	`mb_substr_count('text', 't', 'utf-8');`	`substr_count('text', 't');`
	`mb_substr('text', 0, 123, 'utf-8');`	`substr('text', 0, 123);`
	`mb_convert_case('text', $mode);`	`strtoupper('text');`, `strtolower('text');` or `ucwords('text');` depending on mode

`MBString`

"mb_parse_str": true: You are able to disable any of the supported mb string functions. All supported functions are enabled by default.

Some of the functions are not supported due to complexity to convert them to standard string manipulation functions. Implementing them either does not make sense or creates too many false positive mutations. Not supported functions are mb_ereg*, mb_split, mb_strrichr, mb_get_info and similar.

infection.json:

{
    "mutators": {
        "MBString": {
            "settings": {
                "mb_send_mail": false,
                "mb_substr_count": false
            }
        }
     }
}

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

mutators.md

mutators.md

Function Signature

Unwrap Function

Binary Arithmetic

Round Family

Boolean Substitution

`TrueValue`

Conditional Boundaries

Equal or Identical Checks

Negated Conditionals

Increments

Return Values

Removal Mutators

`ArrayItemRemoval`

Loop

Sorting

Literal Numbers

Exceptions

Type Casting

Regex

Extensions

`MBString`

Files

mutators.md

Latest commit

History

mutators.md

File metadata and controls

Function Signature

Unwrap Function

Binary Arithmetic

Round Family

Boolean Substitution

TrueValue

Conditional Boundaries

Equal or Identical Checks

Negated Conditionals

Increments

Return Values

Removal Mutators

ArrayItemRemoval

Loop

Sorting

Literal Numbers

Exceptions

Type Casting

Regex

Extensions

MBString

`TrueValue`

`ArrayItemRemoval`

`MBString`