Tests reading a single field definition.
function testReadField() {
$field_definition = array(
'field_name' => 'field_1',
'type' => 'test_field',
);
field_create_field($field_definition);
// Read the field back.
$field = field_read_field($field_definition['field_name']);
$this
->assertTrue($field_definition < $field, 'The field was properly read.');
}