PHPUnit style dataProvider in Python unit test

PHPUnit has a handy feature with which you can provide testdata to your tests. This is called a data provider, and is implemented by annotating a test with @dataProvider methodName. Python’s unittest module doesn’t seem to have such a feature.

PHPUnit’s version

The data provider returns a two-dimensional array of test arguments. For example:

class CssParserTest extends PHPUnit_Framework_TestCase {
    function setUp() {
        $this->parser = new CssParser();
    }
 
    /**
     * @dataProvider cssColors
     */
    function testParseColor($color, $notation) {
        $this->assertEquals($color, $this->parser->parseColor($notation));
    }
 
 
    function cssColors() {
        return array(
            array(array(0, 0, 0), '#000'),
            array(array(0, 0, 0), '#000000'),
            array(array(0, 0, 0), 'rgb(0, 0, 0)')
            array(array(0, 0, 0), 'black')
        );
    }
}

Running this test would call the testParseColor() test 4 times, with each of the arrays returned by cssColors() as the arguments.

Python: providing test data using a decorator

While writing tests for some Python code, I discovered that Python’s unittest doesn’t seem to have such a feature. So I implemented my own, using a decorator:

def data_provider(fn_data_provider):
    """Data provider decorator, allows another callable to provide the data for the test"""
    def test_decorator(fn):
        def repl(self, *args):
            for i in fn_data_provider():
                try:
                    fn(self, *i)
                except AssertionError:
                    print "Assertion error caught with data set ", i
                    raise
        return repl
    return test_decorator

Example usage:

class CssParserTest:
    def setUp(self):
        self.parser = CssColor()
 
    colors = lambda: (
        ( (0, 0, 0), '#000' ),
        ( (0, 0, 0), '#000000' ),
        ( (0, 0, 0), 'rgb(0, 0, 0)' ),
        ( (0, 0, 0), 'black' )
    )
 
    @data_provider(colors):
    def test_parse_color(self, color, notation):
        self.assertEquals(color, self.parser.parse_color(notation))

Suggestions of alternatives are greatly appreciated, by the way 🙂

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