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<?php namespace Fake\BuiltIn\Functions; /** * Executes the given statements using fake built-in functions. * * @param callable $statements Statements to execute. * @return mixed Whatever $statements returns. * @throws \ReflectionException */ function fake(callable $statements) { $function = new \ReflectionFunction($statements); $start_line = $function->getStartLine(); $end_line = $function->getEndLine(); $function_source = implode('', array_slice(file($function->getFileName()), $start_line - 1, $end_line - $start_line + 1)); if (preg_match('/(?<={).*(?=})/s', $function_source, $matches)) { $function_body = $matches[0]; $namespace = __NAMESPACE__; return eval(" namespace $namespace; $function_body "); } throw new \RuntimeException('Failed to execute statements.'); } function strlen($string) { return 'fake result'; } namespace My\Name\Space; use function Fake\BuiltIn\Functions\fake; class MyClass { /** * @throws \ReflectionException */ public function testMethodWithFakeStrlen() { fake(function () { echo strlen('foo'), PHP_EOL; }); } public function testMethodWithoutFakeStrlen() { echo strlen('foo'), PHP_EOL; } } $myObject = new MyClass(); try { $myObject->testMethodWithFakeStrlen(); $myObject->testMethodWithoutFakeStrlen(); } catch (\ReflectionException $e) { // ... }