More(3)

NAME
Carp::Assert::More - Convenience assertions for common situations

VERSION
Version 2.9.0

SYNOPSIS
A set of convenience functions for common assertions.

    use Carp::Assert::More;

    my $obj = My::Object;
    assert_isa( $obj, 'My::Object', 'Got back a correct object' );

DESCRIPTION
Carp::Assert::More is a convenient set of assertions to make the habit of writing assertions even easier.

Everything in here is effectively syntactic sugar. There's no technical difference between calling one of these functions:

    assert_datetime( $foo );
    assert_isa( $foo, 'DateTime' );

that are provided by Carp::Assert::More and calling these assertions from Carp::Assert

    assert( defined $foo );
    assert( ref($foo) eq 'DateTime' );

My intent here is to make common assertions easy so that we as programmers have no excuse to not use them.

SIMPLE ASSERTIONS

  assert( $condition [, $name] )
Asserts that $condition is a true value. This is the same as "assert" in "Carp::Assert", provided as a convenience.

  assert_is( $string, $match [,$name] )
Asserts that $string is the same string value as $match.

"undef" is not converted to an empty string. If both strings are "undef", they match. If only one string is "undef", they don't match.

  assert_isnt( $string, $unmatch [,$name] )
Asserts that $string does NOT have the same string value as $unmatch.

"undef" is not converted to an empty string.

  assert_cmp( $x, $op, $y [,$name] )
Asserts that the relation "$x $op $y" is true. It lets you know why the comparsison failed, rather than simply that it did fail, by giving better diagnostics than a plain "assert()", as well as showing the operands in the stacktrace.

Plain "assert()":

    assert( $nitems <= 10, 'Ten items or fewer in the express lane' );

    Assertion (Ten items or fewer in the express lane) failed!
    Carp::Assert::assert("", "Ten items or fewer in the express lane") called at foo.pl line 12

With "assert_cmp()":

    assert_cmp( $nitems, '<=', 10, 'Ten items or fewer in the express lane' );

    Assertion (Ten items or fewer in the express lane) failed!
    Failed: 14 <= 10
    Carp::Assert::More::assert_cmp(14, "<=", 10, "Ten items or fewer in the express lane") called at foo.pl line 11

The following operators are supported:

•   == numeric equal

•   != numeric not equal

•   > numeric greater than

•   >= numeric greater than or equal

•   < numeric less than

•   <= numeric less than or equal

•   lt string less than

•   le string less than or equal

•   gt string less than

•   ge string less than or equal

There is no support for "eq" or "ne" because those already have "assert_is" and "assert_isnt", respectively.

If either $x or $y is undef, the assertion will fail.

If the operator is numeric, and $x or $y are not numbers, the assertion will fail.

  assert_like( $string, qr/regex/ [,$name] )
Asserts that $string matches qr/regex/.

The assertion fails either the string or the regex are undef.

  assert_unlike( $string, qr/regex/ [,$name] )
Asserts that $string matches qr/regex/.

The assertion fails if the regex is undef.

  assert_defined( $this [, $name] )
Asserts that $this is defined.

  assert_undefined( $this [, $name] )
Asserts that $this is not defined.

  assert_nonblank( $this [, $name] )
Asserts that $this is not a reference and is not an empty string.

BOOLEAN ASSERTIONS
These boolean assertions help make diagnostics more useful.

If you use "assert" with a boolean condition:

    assert( $x && $y, 'Both X and Y should be true' );

you can't tell why it failed:

    Assertion (Both X and Y should be true) failed!
     at .../Carp/Assert/More.pm line 123
            Carp::Assert::More::assert(undef, 'Both X and Y should be true') called at foo.pl line 16

But if you use "assert_and":

    assert_and( $x, $y, 'Both X and Y should be true' );

the stacktrace tells you which half of the expression failed.

    Assertion (Both X and Y should be true) failed!
     at .../Carp/Assert/More.pm line 123
            Carp::Assert::More::assert_and('thing', undef, 'Both X and Y should be true') called at foo.pl line 16

  assert_and( $x, $y [, $name] )
Asserts that both $x and $y are true.

  assert_or( $x, $y [, $name] )
Asserts that at least one of $x or $y are true.

  assert_xor( $x, $y [, $name] )
Asserts that $x is true, or $y is true, but not both.

NUMERIC ASSERTIONS

  assert_numeric( $n [, $name] )
Asserts that $n looks like a number, according to "Scalar::Util::looks_like_number". "undef" will always fail.

  assert_integer( $this [, $name ] )
Asserts that $this is an integer, which may be zero or negative.

    assert_integer( 0 );      # pass
    assert_integer( 14 );     # pass
    assert_integer( -14 );    # pass
    assert_integer( '14.' );  # FAIL

  assert_nonzero( $this [, $name ] )
Asserts that the numeric value of $this is defined and is not zero.

    assert_nonzero( 0 );    # FAIL
    assert_nonzero( -14 );  # pass
    assert_nonzero( '14.' );  # pass

  assert_positive( $this [, $name ] )
Asserts that $this is defined, numeric and greater than zero.

    assert_positive( 0 );    # FAIL
    assert_positive( -14 );  # FAIL
    assert_positive( '14.' );  # pass

  assert_nonnegative( $this [, $name ] )
Asserts that $this is defined, numeric and greater than or equal to zero.

    assert_nonnegative( 0 );      # pass
    assert_nonnegative( -14 );    # FAIL
    assert_nonnegative( '14.' );  # pass
    assert_nonnegative( 'dog' );  # pass

  assert_negative( $this [, $name ] )
Asserts that the numeric value of $this is defined and less than zero.

    assert_negative( 0 );       # FAIL
    assert_negative( -14 );     # pass
    assert_negative( '14.' );   # FAIL

  assert_nonzero_integer( $this [, $name ] )
Asserts that the numeric value of $this is defined, an integer, and not zero.

    assert_nonzero_integer( 0 );      # FAIL
    assert_nonzero_integer( -14 );    # pass
    assert_nonzero_integer( '14.' );  # FAIL

  assert_positive_integer( $this [, $name ] )
Asserts that the numeric value of $this is defined, an integer and greater than zero.

    assert_positive_integer( 0 );     # FAIL
    assert_positive_integer( -14 );   # FAIL
    assert_positive_integer( '14.' ); # FAIL
    assert_positive_integer( '14' );  # pass

  assert_nonnegative_integer( $this [, $name ] )
Asserts that the numeric value of $this is defined, an integer, and not less than zero.

    assert_nonnegative_integer( 0 );      # pass
    assert_nonnegative_integer( -14 );    # FAIL
    assert_nonnegative_integer( '14.' );  # FAIL

  assert_negative_integer( $this [, $name ] )
Asserts that the numeric value of $this is defined, an integer, and less than zero.

    assert_negative_integer( 0 );      # FAIL
    assert_negative_integer( -14 );    # pass
    assert_negative_integer( '14.' );  # FAIL

  assert_numeric_between( $n, $lo, $hi [, $name ] )
Asserts that the value of $this is defined, numeric and between $lo and $hi, inclusive.

    assert_numeric_between( 15, 10, 100 );  # pass
    assert_numeric_between( 10, 15, 100 );  # FAIL
    assert_numeric_between( 3.14, 1, 10 );  # pass

  assert_integer_between( $n, $lo, $hi [, $name ] )
Asserts that the value of $this is defined, an integer, and between $lo and $hi, inclusive.

    assert_integer_between( 15, 10, 100 );  # pass
    assert_integer_between( 10, 15, 100 );  # FAIL
    assert_integer_between( 3.14, 1, 10 );  # FAIL

REFERENCE ASSERTIONS

  assert_isa( $this, $type [, $name ] )
Asserts that $this is an object of type $type.

  assert_isa_in( $obj, \@types [, $description] )
Assert that the blessed $obj isa one of the types in "\@types".

    assert_isa_in( $obj, [ 'My::Foo', 'My::Bar' ], 'Must pass either a Foo or Bar object' );

  assert_empty( $this [, $name ] )
$this must be a ref to either a hash or an array. Asserts that that collection contains no elements. Will assert (with its own message, not $name) unless given a hash or array ref. It is OK if $this has been blessed into objecthood, but the semantics of checking an object to see if it does not have keys (for a hashref) or returns 0 in scalar context (for an array ref) may not be what you want.

    assert_empty( 0 );       # FAIL
    assert_empty( 'foo' );   # FAIL
    assert_empty( undef );   # FAIL
    assert_empty( {} );      # pass
    assert_empty( [] );      # pass
    assert_empty( {foo=>1} );# FAIL
    assert_empty( [1,2,3] ); # FAIL

  assert_nonempty( $this [, $name ] )
$this must be a ref to either a hash or an array. Asserts that that collection contains at least 1 element. Will assert (with its own message, not $name) unless given a hash or array ref. It is OK if $this has been blessed into objecthood, but the semantics of checking an object to see if it has keys (for a hashref) or returns >0 in scalar context (for an array ref) may not be what you want.

    assert_nonempty( 0 );       # FAIL
    assert_nonempty( 'foo' );   # FAIL
    assert_nonempty( undef );   # FAIL
    assert_nonempty( {} );      # FAIL
    assert_nonempty( [] );      # FAIL
    assert_nonempty( {foo=>1} );# pass
    assert_nonempty( [1,2,3] ); # pass

  assert_nonref( $this [, $name ] )
Asserts that $this is not undef and not a reference.

  assert_hashref( $ref [,$name] )
Asserts that $ref is defined, and is a reference to a (possibly empty) hash.

NB: This method returns false for objects, even those whose underlying data is a hashref. This is as it should be, under the assumptions that:

(a) you shouldn't rely on the underlying data structure of a particular class, and

(b) you should use "assert_isa" instead.

  assert_hashref_nonempty( $ref [,$name] )
Asserts that $ref is defined and is a reference to a hash with at least one key/value pair.

  assert_arrayref( $ref [, $name] )

  assert_listref( $ref [,$name] )
Asserts that $ref is defined, and is a reference to an array, which may or may not be empty.

NB: The same caveat about objects whose underlying structure is a hash (see "assert_hashref") applies here; this method returns false even for objects whose underlying structure is an array.

"assert_listref" is an alias for "assert_arrayref" and may go away in the future. Use "assert_arrayref" instead.

  assert_arrayref_nonempty( $ref [, $name] )
Asserts that $ref is reference to an array that has at least one element in it.

  assert_arrayref_of( $ref, $type [, $name] )
Asserts that $ref is reference to an array, and any/all elements are of type $type.

For example:

    my @users = get_users();
    assert_arrayref_of( \@users, 'My::User' );

  assert_arrayref_nonempty_of( $ref, $type [, $name] )
Asserts that $ref is reference to an array, that it has at least one element, and that all elements are of type $type.

This is the same function as "assert_arrayref_of", except that it also requires at least one element.

  assert_arrayref_all( $aref, $sub [, $name] )
Asserts that $aref is reference to an array that has at least one element in it. Each element of the array is passed to subroutine $sub which is assumed to be an assertion.

For example:

    my $aref_of_counts = get_counts();
    assert_arrayref_all( $aref, \&assert_positive_integer, 'Counts are positive' );

Whatever is passed as $name, a string saying "Element #N" will be appended, where N is the zero-based index of the array.

  assert_aoh( $ref [, $name ] )
Verifies that $array is an arrayref, and that every element is a hashref.

The array $array can be an empty arraref and the assertion will pass.

  assert_coderef( $ref [,$name] )
Asserts that $ref is defined, and is a reference to a closure.

  assert_regex( $ref [,$name] )
Asserts that $ref is defined, and is a reference to a regex.

It is functionally the same as "assert_isa( $ref, 'Regexp' )".

TYPE-SPECIFIC ASSERTIONS

  assert_datetime( $date )
Asserts that $date is a DateTime object.

SET AND HASH MEMBERSHIP

  assert_in( $string, \@inlist [,$name] );
Asserts that $string matches one of the elements of \@inlist. $string may be undef.

\@inlist must be an array reference of non-ref strings. If any element is a reference, the assertion fails.

  assert_exists( \%hash, $key [,$name] )

  assert_exists( \%hash, \@keylist [,$name] )
Asserts that %hash is indeed a hash, and that $key exists in %hash, or that all of the keys in @keylist exist in %hash.

    assert_exists( \%custinfo, 'name', 'Customer has a name field' );

    assert_exists( \%custinfo, [qw( name addr phone )],
                            'Customer has name, address and phone' );

  assert_lacks( \%hash, $key [,$name] )

  assert_lacks( \%hash, \@keylist [,$name] )
Asserts that %hash is indeed a hash, and that $key does NOT exist in %hash, or that none of the keys in @keylist exist in %hash. The list @keylist cannot be empty.

    assert_lacks( \%users, 'root', 'Root is not in the user table' );

    assert_lacks( \%users, [qw( root admin nobody )], 'No bad usernames found' );

  assert_all_keys_in( \%hash, \@names [, $name ] )
Asserts that each key in %hash is in the list of @names.

This is used to ensure that there are no extra keys in a given hash.

    assert_all_keys_in( $obj, [qw( height width depth )], '$obj can only contain height, width and depth keys' );

You can pass an empty list of @names.

  assert_keys_are( \%hash, \@keys [, $name ] )
Asserts that the keys for %hash are exactly @keys, no more and no less.

CONTEXT ASSERTIONS

  assert_context_nonvoid( [$name] )
Verifies that the function currently being executed has not been called in void context. This is to ensure the calling function is not ignoring the return value of the executing function.

Given this function:

    sub something {
        ...

        assert_context_nonvoid();

        return $important_value;
    }

These calls to "something" will pass:

    my $val = something();
    my @things = something();

but this will fail:

    something();

If the $name argument is not passed, a default message of "<funcname> must not be called in void context" is provided.

  assert_context_void( [$name] )
Verifies that the function currently being executed has been called in void context. This is for functions that do not return anything meaningful.

Given this function:

    sub something {
        ...

        assert_context_void();

        return; # No meaningful value.
    }

These calls to "something" will fail:

    my $val = something();
    my @things = something();

but this will pass:

    something();

If the $name argument is not passed, a default message of "<funcname> must be called in void context" is provided.

  assert_context_scalar( [$name] )
Verifies that the function currently being executed has been called in scalar context. This is to ensure the calling function is not ignoring the return value of the executing function.

Given this function:

    sub something {
        ...

        assert_context_scalar();

        return $important_value;
    }

This call to "something" will pass:

    my $val = something();

but these will fail:

    something();
    my @things = something();

If the $name argument is not passed, a default message of "<funcname> must be called in scalar context" is provided.

  assert_context_list( [$name] )
Verifies that the function currently being executed has been called in list context.

Given this function:

    sub something {
        ...

        assert_context_scalar();

        return @values;
    }

This call to "something" will pass:

    my @vals = something();

but these will fail:

    something();
    my $thing = something();

If the $name argument is not passed, a default message of "<funcname> must be called in list context" is provided.

UTILITY ASSERTIONS

  assert_fail( [$name] )
Assertion that always fails. "assert_fail($msg)" is exactly the same as calling "assert(0,$msg)", but it eliminates that case where you accidentally use "assert($msg)", which of course never fires.

COPYRIGHT & LICENSE
Copyright 2005-2025 Andy Lester

This program is free software; you can redistribute it and/or modify it under the terms of the Artistic License version 2.0.

ACKNOWLEDGEMENTS
Thanks to Eric A. Zarko, Bob Diss, Pete Krawczyk, David Storrs, Dan Friedman, Allard Hoeve, Thomas L. Shinnick, and Leland Johnson for code and fixes.