public function testWithMutableTrue() { // Arrange $bigNumber = new BigNumber('-5', 10, true); // Act $newBigNumber = $bigNumber->abs(); // Assert $this->assertInstanceOf('PHP\\Math\\BigNumber\\BigNumber', $bigNumber); $this->assertInstanceOf('PHP\\Math\\BigNumber\\BigNumber', $newBigNumber); $this->assertEquals('5', $bigNumber->getValue()); $this->assertEquals('5', $newBigNumber->getValue()); }