public function test_remove_all_filter() {
    $a   = new MockAction();
    $tag = __FUNCTION__;
    $val = __FUNCTION__ . '_val';

    add_filter( 'all', array( $a, 'filterall' ) );
    $this->assertTrue( has_filter( 'all' ) );
    $this->assertSame( 10, has_filter( 'all', array( $a, 'filterall' ) ) );
    $this->assertSame( $val, apply_filters( $tag, $val ) );

    // Make sure our hook was called correctly.
    $this->assertSame( 1, $a->get_call_count() );
    $this->assertSame( array( $tag ), $a->get_tags() );

    // Now remove the filter, do it again, and make sure it's not called this time.
    remove_filter( 'all', array( $a, 'filterall' ) );
    $this->assertFalse( has_filter( 'all', array( $a, 'filterall' ) ) );
    $this->assertFalse( has_filter( 'all' ) );
    $this->assertSame( $val, apply_filters( $tag, $val ) );
    // Call cound should remain at 1.
    $this->assertSame( 1, $a->get_call_count() );
    $this->assertSame( array( $tag ), $a->get_tags() );
  }