Test reading back an instance definition.
function testReadFieldInstance() {
field_create_instance($this->instance_definition);
// Read the instance back.
$instance = field_read_instance('test_entity', $this->instance_definition['field_name'], $this->instance_definition['bundle']);
$this
->assertTrue($this->instance_definition['field_name'] == $instance['field_name'], 'The field was properly read.');
$this
->assertTrue($this->instance_definition['entity_type'] == $instance['entity_type'], 'The field was properly read.');
$this
->assertTrue($this->instance_definition['bundle'] == $instance['bundle'], 'The field was properly read.');
}