Document and test stacking of parametrize.

Closes #815.

doc/en/parametrize.txt

@@ -114,6 +114,18 @@ Let's run this::
 The one parameter set which caused a failure previously now
 shows up as an "xfailed (expected to fail)" test.
 
+To get all combinations of multiple parametrized arguments you can stack
+``parametrize`` decorators::
+
+    import pytest
+    @pytest.mark.parametrize("x", [0, 1])
+    @pytest.mark.parametrize("y", [2, 3])
+    def test_foo(x, y):
+        pass
+
+This will run the test with the arguments set to x=0/y=2, x=0/y=3, x=1/y=2 and
+x=1/y=3.
+
 .. note::
 
     In versions prior to 2.4 one needed to specify the argument

testing/python/collect.py

@@ -472,6 +472,20 @@ class TestFunction:
         config.pluginmanager.register(MyPlugin2())
         config.hook.pytest_pyfunc_call(pyfuncitem=item)
 
+    def test_multiple_parametrize(self, testdir):
+        modcol = testdir.getmodulecol("""
+            import pytest
+            @pytest.mark.parametrize('x', [0, 1])
+            @pytest.mark.parametrize('y', [2, 3])
+            def test1(x, y):
+                pass
+        """)
+        colitems = modcol.collect()
+        assert colitems[0].name == 'test1[2-0]'
+        assert colitems[1].name == 'test1[2-1]'
+        assert colitems[2].name == 'test1[3-0]'
+        assert colitems[3].name == 'test1[3-1]'
+
     def test_issue751_multiple_parametrize_with_ids(self, testdir):
         modcol = testdir.getmodulecol("""
             import pytest