pytest_make_parametrize_id hook

CHANGELOG.rst

@@ -27,7 +27,8 @@
   whether to filter the traceback based on the ``ExceptionInfo`` object passed
   to it.
 
-*
+* New ``pytest_make_parametrize_id`` hook.
+  Thanks `@palaviv`_ for the PR.
 
 **Changes**
 

_pytest/hookspec.py

@@ -156,6 +156,12 @@ def pytest_pyfunc_call(pyfuncitem):
 def pytest_generate_tests(metafunc):
     """ generate (multiple) parametrized calls to a test function."""
 
+@hookspec(firstresult=True)
+def pytest_make_parametrize_id(config, val):
+    """Return a user-friendly string representation of the given ``val`` that will be used
+    by @pytest.mark.parametrize calls. Return None if the hook doesn't know about ``val``.
+    """
+
 # -------------------------------------------------------------------------
 # generic runtest related hooks
 # -------------------------------------------------------------------------

_pytest/python.py

@@ -342,6 +342,9 @@ def pytest_pycollect_makeitem(collector, name, obj):
                 res = list(collector._genfunctions(name, obj))
             outcome.force_result(res)
 
+def pytest_make_parametrize_id(config, val):
+    return None
+
 def is_generator(func):
     try:
         return _pytest._code.getrawcode(func).co_flags & 32 # generator function
@@ -1030,7 +1033,7 @@ def parametrize(self, argnames, argvalues, indirect=False, ids=None,
         if ids and len(ids) != len(argvalues):
             raise ValueError('%d tests specified with %d ids' %(
                              len(argvalues), len(ids)))
-        ids = idmaker(argnames, argvalues, idfn, ids)
+        ids = idmaker(argnames, argvalues, idfn, ids, self.config)
         newcalls = []
         for callspec in self._calls or [CallSpec2(self)]:
             for param_index, valset in enumerate(argvalues):
@@ -1130,7 +1133,7 @@ def _escape_strings(val):
             return val.encode('unicode-escape')
 
 
-def _idval(val, argname, idx, idfn):
+def _idval(val, argname, idx, idfn, config=None):
     if idfn:
         try:
             s = idfn(val)
@@ -1139,6 +1142,11 @@ def _idval(val, argname, idx, idfn):
         except Exception:
             pass
 
+    if config:
+        hook_id = config.hook.pytest_make_parametrize_id(config=config, val=val)
+        if hook_id:
+            return hook_id
+
     if isinstance(val, (bytes, str)) or (_PY2 and isinstance(val, unicode)):
         return _escape_strings(val)
     elif isinstance(val, (float, int, bool, NoneType)):
@@ -1151,16 +1159,16 @@ def _idval(val, argname, idx, idfn):
         return val.__name__
     return str(argname)+str(idx)
 
-def _idvalset(idx, valset, argnames, idfn, ids):
+def _idvalset(idx, valset, argnames, idfn, ids, config=None):
     if ids is None or ids[idx] is None:
-        this_id = [_idval(val, argname, idx, idfn)
+        this_id = [_idval(val, argname, idx, idfn, config)
                    for val, argname in zip(valset, argnames)]
         return "-".join(this_id)
     else:
         return _escape_strings(ids[idx])
 
-def idmaker(argnames, argvalues, idfn=None, ids=None):
-    ids = [_idvalset(valindex, valset, argnames, idfn, ids)
+def idmaker(argnames, argvalues, idfn=None, ids=None, config=None):
+    ids = [_idvalset(valindex, valset, argnames, idfn, ids, config)
            for valindex, valset in enumerate(argvalues)]
     if len(set(ids)) != len(ids):
         # The ids are not unique

doc/en/writing_plugins.rst

@@ -470,6 +470,7 @@ you can use the following hook:
 
 .. autofunction:: pytest_pycollect_makeitem
 .. autofunction:: pytest_generate_tests
+.. autofunction:: pytest_make_parametrize_id
 
 After collection is complete, you can modify the order of
 items, delete or otherwise amend the test items:

testing/python/metafunc.py

@@ -1156,3 +1156,21 @@ def test_limit(limit, myfixture):
         """)
         reprec = testdir.inline_run()
         reprec.assertoutcome(passed=2)
+
+    def test_pytest_make_parametrize_id(self, testdir):
+        testdir.makeconftest("""
+            def pytest_make_parametrize_id(config, val):
+                return str(val * 2)
+        """)
+        testdir.makepyfile("""
+                import pytest
+
+                @pytest.mark.parametrize("x", range(2))
+                def test_func(x):
+                    pass
+                """)
+        result = testdir.runpytest("-v")
+        result.stdout.fnmatch_lines([
+            "*test_func*0*PASS*",
+            "*test_func*2*PASS*",
+        ])