Port tests to pytest

Use simple asserts and pytest's powerful introspection to make testing
simpler. This merges the old .py/.ref file pairs into simple .py files
where the expected values are right next to the code being tested.

This commit does not touch the C++ part of the code and replicates the
Python tests exactly like the old .ref-file-based approach.

tests/test_virtual_functions.py

@@ -0,0 +1,227 @@
+import pytest
+from pybind11_tests import ConstructorStats
+
+
+def test_override(capture, msg):
+    from pybind11_tests import (ExampleVirt, runExampleVirt, runExampleVirtVirtual,
+                                runExampleVirtBool)
+
+    class ExtendedExampleVirt(ExampleVirt):
+        def __init__(self, state):
+            super(ExtendedExampleVirt, self).__init__(state + 1)
+            self.data = "Hello world"
+
+        def run(self, value):
+            print('ExtendedExampleVirt::run(%i), calling parent..' % value)
+            return super(ExtendedExampleVirt, self).run(value + 1)
+
+        def run_bool(self):
+            print('ExtendedExampleVirt::run_bool()')
+            return False
+
+        def pure_virtual(self):
+            print('ExtendedExampleVirt::pure_virtual(): %s' % self.data)
+
+    ex12 = ExampleVirt(10)
+    with capture:
+        assert runExampleVirt(ex12, 20) == 30
+    assert capture == "Original implementation of ExampleVirt::run(state=10, value=20)"
+
+    with pytest.raises(RuntimeError) as excinfo:
+        runExampleVirtVirtual(ex12)
+    assert msg(excinfo.value) == 'Tried to call pure virtual function "ExampleVirt::pure_virtual"'
+
+    ex12p = ExtendedExampleVirt(10)
+    with capture:
+        assert runExampleVirt(ex12p, 20) == 32
+    assert capture == """
+        ExtendedExampleVirt::run(20), calling parent..
+        Original implementation of ExampleVirt::run(state=11, value=21)
+    """
+    with capture:
+        assert runExampleVirtBool(ex12p) is False
+    assert capture == "ExtendedExampleVirt::run_bool()"
+    with capture:
+        runExampleVirtVirtual(ex12p)
+    assert capture == "ExtendedExampleVirt::pure_virtual(): Hello world"
+
+    cstats = ConstructorStats.get(ExampleVirt)
+    assert cstats.alive() == 2
+    del ex12, ex12p
+    assert cstats.alive() == 0
+    assert cstats.values() == ['10', '11']
+    assert cstats.copy_constructions == 0
+    assert cstats.move_constructions >= 0
+
+
+def test_inheriting_repeat(capture):
+    from pybind11_tests import A_Repeat, B_Repeat, C_Repeat, D_Repeat, A_Tpl, B_Tpl, C_Tpl, D_Tpl
+
+    class VI_AR(A_Repeat):
+        def unlucky_number(self):
+            return 99
+
+    class VI_AT(A_Tpl):
+        def unlucky_number(self):
+            return 999
+
+    obj = VI_AR()
+    with capture:
+        obj.say_something(3)
+    assert capture == "hihihi"
+    assert obj.unlucky_number() == 99
+
+    obj = VI_AT()
+    with capture:
+        obj.say_something(3)
+    assert capture == "hihihi"
+    assert obj.unlucky_number() == 999
+
+    for obj in [B_Repeat(), B_Tpl()]:
+        with capture:
+            obj.say_something(3)
+        assert capture == "B says hi 3 times"
+        assert obj.unlucky_number() == 13
+        assert obj.lucky_number() == 7.0
+
+    for obj in [C_Repeat(), C_Tpl()]:
+        with capture:
+            obj.say_something(3)
+        assert capture == "B says hi 3 times"
+        assert obj.unlucky_number() == 4444
+        assert obj.lucky_number() == 888.0
+
+    class VI_CR(C_Repeat):
+        def lucky_number(self):
+            return C_Repeat.lucky_number(self) + 1.25
+
+    obj = VI_CR()
+    with capture:
+        obj.say_something(3)
+    assert capture == "B says hi 3 times"
+    assert obj.unlucky_number() == 4444
+    assert obj.lucky_number() == 889.25
+
+    class VI_CT(C_Tpl):
+        pass
+
+    obj = VI_CT()
+    with capture:
+        obj.say_something(3)
+    assert capture == "B says hi 3 times"
+    assert obj.unlucky_number() == 4444
+    assert obj.lucky_number() == 888.0
+
+    class VI_CCR(VI_CR):
+        def lucky_number(self):
+            return VI_CR.lucky_number(self) * 10
+
+    obj = VI_CCR()
+    with capture:
+        obj.say_something(3)
+    assert capture == "B says hi 3 times"
+    assert obj.unlucky_number() == 4444
+    assert obj.lucky_number() == 8892.5
+
+    class VI_CCT(VI_CT):
+        def lucky_number(self):
+            return VI_CT.lucky_number(self) * 1000
+
+    obj = VI_CCT()
+    with capture:
+        obj.say_something(3)
+    assert capture == "B says hi 3 times"
+    assert obj.unlucky_number() == 4444
+    assert obj.lucky_number() == 888000.0
+
+    class VI_DR(D_Repeat):
+        def unlucky_number(self):
+            return 123
+
+        def lucky_number(self):
+            return 42.0
+
+    for obj in [D_Repeat(), D_Tpl()]:
+        with capture:
+            obj.say_something(3)
+        assert capture == "B says hi 3 times"
+        assert obj.unlucky_number() == 4444
+        assert obj.lucky_number() == 888.0
+
+    obj = VI_DR()
+    with capture:
+        obj.say_something(3)
+    assert capture == "B says hi 3 times"
+    assert obj.unlucky_number() == 123
+    assert obj.lucky_number() == 42.0
+
+    class VI_DT(D_Tpl):
+        def say_something(self, times):
+            print("VI_DT says:" + (' quack' * times))
+
+        def unlucky_number(self):
+            return 1234
+
+        def lucky_number(self):
+            return -4.25
+
+    obj = VI_DT()
+    with capture:
+        obj.say_something(3)
+    assert capture == "VI_DT says: quack quack quack"
+    assert obj.unlucky_number() == 1234
+    assert obj.lucky_number() == -4.25
+
+
+def test_move_support(capture, msg):
+    from pybind11_tests import NCVirt, NonCopyable, Movable
+
+    class NCVirtExt(NCVirt):
+        def get_noncopyable(self, a, b):
+            # Constructs and returns a new instance:
+            nc = NonCopyable(a*a, b*b)
+            return nc
+
+        def get_movable(self, a, b):
+            # Return a referenced copy
+            self.movable = Movable(a, b)
+            return self.movable
+
+    class NCVirtExt2(NCVirt):
+        def get_noncopyable(self, a, b):
+            # Keep a reference: this is going to throw an exception
+            self.nc = NonCopyable(a, b)
+            return self.nc
+
+        def get_movable(self, a, b):
+            # Return a new instance without storing it
+            return Movable(a, b)
+
+    ncv1 = NCVirtExt()
+    with capture:
+        ncv1.print_nc(2, 3)
+    assert capture == "36"
+    with capture:
+        ncv1.print_movable(4, 5)
+    assert capture == "9"
+    ncv2 = NCVirtExt2()
+    with capture:
+        ncv2.print_movable(7, 7)
+    assert capture == "14"
+    # Don't check the exception message here because it differs under debug/non-debug mode
+    with pytest.raises(RuntimeError):
+        ncv2.print_nc(9, 9)
+
+    nc_stats = ConstructorStats.get(NonCopyable)
+    mv_stats = ConstructorStats.get(Movable)
+    assert nc_stats.alive() == 1
+    assert mv_stats.alive() == 1
+    del ncv1, ncv2
+    assert nc_stats.alive() == 0
+    assert mv_stats.alive() == 0
+    assert nc_stats.values() == ['4', '9', '9', '9']
+    assert mv_stats.values() == ['4', '5', '7', '7']
+    assert nc_stats.copy_constructions == 0
+    assert mv_stats.copy_constructions == 1
+    assert nc_stats.move_constructions >= 0
+    assert mv_stats.move_constructions >= 0