isMissing example

public function testGetRequiredOptions()
    {
        $this->resolver->setRequired(['foo', 'bar']);
        $this->resolver->setDefault('bam', 'baz');
        $this->resolver->setDefault('foo', 'boo');

        $this->assertSame(['foo', 'bar'], $this->resolver->getRequiredOptions());
    }

    public function testIsMissingIfNotSet()
    {
        $this->assertFalse($this->resolver->isMissing('foo'));
        $this->resolver->setRequired('foo');
        $this->assertTrue($this->resolver->isMissing('foo'));
    }

    public function testIsNotMissingIfSet()
    {
        $this->resolver->setDefault('foo', 'bar');

        $this->assertFalse($this->resolver->isMissing('foo'));
        $this->resolver->setRequired('foo');
        $this->assertFalse($this->resolver->isMissing('foo'));
    }