[11.x] Add some tests to SupportStrTest

[saMahmoudzadeh]

This PR, Add some tests to SupportStrTest.php

testStringAscii()

// the empty string and a combination of letters, numbers, and special characters have been tested.
$this->assertSame('', Str::ascii(''));
$this->assertSame('a!2e', Str::ascii('a!2ë'));

testStrBefore()

// test empty string, and first character
$this->assertSame('', Str::before('', ''));
$this->assertSame('', Str::before('', 'a'));
$this->assertSame('', Str::before('a', 'a'));

// testing the search for the special character '@'
$this->assertSame('foo', Str::before('foo@bar.com', '@'));
$this->assertSame('foo', Str::before('foo@@bar.com', '@'));
$this->assertSame('', Str::before('@foo@bar.com', '@'));

testStrBetween()

// testing numbers
$this->assertSame('234', Str::between('12345', 1, 5));
$this->assertSame('45', Str::between('123456789', '123', '6789'));

// testing the scenario where 'foo' and 'bar' are not found within the string 'nothing'.
$this->assertSame('nothing', Str::between('nothing', 'foo', 'bar'));

Thanks!