feat(verify): allow specification of exact call count (#27)

Closes #23

Author: mcous

decoy/__init__.py

@@ -150,14 +150,18 @@ def when(self, _rehearsal_result: ReturnT) -> Stub[ReturnT]:
 
         return stub
 
-    def verify(self, *_rehearsal_results: Any) -> None:
+    def verify(self, *_rehearsal_results: Any, times: Optional[int] = None) -> None:
         """Verify a decoy was called using one or more rehearsals.
 
         See [verification usage guide](../usage/verify) for more details.
 
         Arguments:
             _rehearsal_results: The return value of rehearsals, unused except
                 to determine how many rehearsals to verify.
+            times: How many times the call should appear. If `times` is specifed,
+                the call count must match exactly, otherwise the call must appear
+                at least once. The `times` argument must be used with exactly one
+                rehearsal.
 
         Example:
             ```python
@@ -187,14 +191,24 @@ def test_create_something(decoy: Decoy):
         all_spies = [r.spy_id for r in rehearsals]
         all_calls = self._registry.get_calls_by_spy_id(*all_spies)
 
-        for i in range(len(all_calls)):
-            call = all_calls[i]
-            call_list = all_calls[i : i + len(rehearsals)]
+        if times is None:
+            for i in range(len(all_calls)):
+                call = all_calls[i]
+                call_list = all_calls[i : i + len(rehearsals)]
 
-            if call == rehearsals[0] and call_list == rehearsals:
+                if call == rehearsals[0] and call_list == rehearsals:
+                    return None
+
+        elif len(rehearsals) == 1:
+            matching_calls = [call for call in all_calls if call == rehearsals[0]]
+
+            if len(matching_calls) == times:
                 return None
 
-        raise AssertionError(self._build_verify_error(rehearsals, all_calls))
+        else:
+            raise ValueError("Cannot verify multiple rehearsals when using times")
+
+        raise AssertionError(self._build_verify_error(rehearsals, all_calls, times))
 
     def _pop_last_rehearsal(self) -> SpyCall:
         rehearsal = self._registry.pop_last_call()
@@ -221,10 +235,14 @@ def _handle_spy_call(self, call: SpyCall) -> Any:
         return None
 
     def _build_verify_error(
-        self, rehearsals: Sequence[SpyCall], all_calls: Sequence[SpyCall]
+        self,
+        rehearsals: Sequence[SpyCall],
+        all_calls: Sequence[SpyCall],
+        times: Optional[int] = None,
     ) -> str:
         rehearsals_len = len(rehearsals)
         rehearsals_plural = rehearsals_len != 1
+        times_plural = times is not None and times != 1
 
         all_calls_len = len(all_calls)
         all_calls_plural = all_calls_len != 1
@@ -239,7 +257,8 @@ def _build_verify_error(
 
         return linesep.join(
             [
-                f"Expected call{'s' if rehearsals_plural else ''}:",
+                f"Expected {f'{times} ' if times is not None else ''}"
+                f"call{'s' if rehearsals_plural or times_plural else ''}:",
                 rehearsals_printout,
                 f"Found {all_calls_len} call{'s' if all_calls_plural else ''}:",
                 all_calls_printout,

docs/usage/verify.md

@@ -55,3 +55,21 @@ decoy.verify(
     handler.call_second_procedure("world"),
 )
 ```
+
+## Verifying a call count
+
+You may want to verify that a call has been made a certain number of times, or verify that a call was never made. You can use the optional `times` argument to specify call count.
+
+```python
+decoy.verify(
+    handler.should_be_called_twice(),
+    times=2,
+)
+
+decoy.verify(
+    handler.should_never_be_called(),
+    times=0,
+)
+```
+
+You may only use the `times` argument with single rehearsal.

tests/test_verify.py

@@ -8,16 +8,16 @@
 
 def test_call_function_then_verify(decoy: Decoy) -> None:
     """It should be able to verify a past function call."""
-    stub = decoy.create_decoy_func(spec=some_func)
+    spy = decoy.create_decoy_func(spec=some_func)
 
-    stub("hello")
-    stub("goodbye")
+    spy("hello")
+    spy("goodbye")
 
-    decoy.verify(stub("hello"))
-    decoy.verify(stub("goodbye"))
+    decoy.verify(spy("hello"))
+    decoy.verify(spy("goodbye"))
 
     with pytest.raises(AssertionError) as error_info:
-        decoy.verify(stub("fizzbuzz"))
+        decoy.verify(spy("fizzbuzz"))
 
     assert str(error_info.value) == (
         f"Expected call:{linesep}"
@@ -30,21 +30,21 @@ def test_call_function_then_verify(decoy: Decoy) -> None:
 
 def test_call_method_then_verify(decoy: Decoy) -> None:
     """It should be able to verify a past method call."""
-    stub = decoy.create_decoy(spec=SomeClass)
+    spy = decoy.create_decoy(spec=SomeClass)
 
-    stub.foo("hello")
-    stub.foo("goodbye")
-    stub.bar(0, 1.0, "2")
-    stub.bar(3, 4.0, "5")
+    spy.foo("hello")
+    spy.foo("goodbye")
+    spy.bar(0, 1.0, "2")
+    spy.bar(3, 4.0, "5")
 
-    decoy.verify(stub.foo("hello"))
-    decoy.verify(stub.foo("goodbye"))
+    decoy.verify(spy.foo("hello"))
+    decoy.verify(spy.foo("goodbye"))
 
-    decoy.verify(stub.bar(0, 1.0, "2"))
-    decoy.verify(stub.bar(3, 4.0, "5"))
+    decoy.verify(spy.bar(0, 1.0, "2"))
+    decoy.verify(spy.bar(3, 4.0, "5"))
 
     with pytest.raises(AssertionError) as error_info:
-        decoy.verify(stub.foo("fizzbuzz"))
+        decoy.verify(spy.foo("fizzbuzz"))
 
     assert str(error_info.value) == (
         f"Expected call:{linesep}"
@@ -55,7 +55,7 @@ def test_call_method_then_verify(decoy: Decoy) -> None:
     )
 
     with pytest.raises(AssertionError) as error_info:
-        decoy.verify(stub.bar(6, 7.0, "8"))
+        decoy.verify(spy.bar(6, 7.0, "8"))
 
     assert str(error_info.value) == (
         f"Expected call:{linesep}"
@@ -68,14 +68,14 @@ def test_call_method_then_verify(decoy: Decoy) -> None:
 
 def test_verify_with_matcher(decoy: Decoy) -> None:
     """It should still work with matchers as arguments."""
-    stub = decoy.create_decoy_func(spec=some_func)
+    spy = decoy.create_decoy_func(spec=some_func)
 
-    stub("hello")
+    spy("hello")
 
-    decoy.verify(stub(matchers.StringMatching("ell")))
+    decoy.verify(spy(matchers.StringMatching("ell")))
 
     with pytest.raises(AssertionError) as error_info:
-        decoy.verify(stub(matchers.StringMatching("^ell")))
+        decoy.verify(spy(matchers.StringMatching("^ell")))
 
     assert str(error_info.value) == (
         f"Expected call:{linesep}"
@@ -87,48 +87,48 @@ def test_verify_with_matcher(decoy: Decoy) -> None:
 
 def test_call_nested_method_then_verify(decoy: Decoy) -> None:
     """It should be able to verify a past nested method call."""
-    stub = decoy.create_decoy(spec=SomeNestedClass)
+    spy = decoy.create_decoy(spec=SomeNestedClass)
 
-    stub.child.foo("hello")
-    stub.child.bar(0, 1.0, "2")
+    spy.child.foo("hello")
+    spy.child.bar(0, 1.0, "2")
 
-    decoy.verify(stub.child.foo("hello"))
-    decoy.verify(stub.child.bar(0, 1.0, "2"))
+    decoy.verify(spy.child.foo("hello"))
+    decoy.verify(spy.child.bar(0, 1.0, "2"))
 
     with pytest.raises(AssertionError):
-        decoy.verify(stub.foo("fizzbuzz"))
+        decoy.verify(spy.foo("fizzbuzz"))
 
 
 def test_call_no_return_method_then_verify(decoy: Decoy) -> None:
     """It should be able to verify a past void method call."""
-    stub = decoy.create_decoy(spec=SomeClass)
+    spy = decoy.create_decoy(spec=SomeClass)
 
-    stub.do_the_thing(True)
+    spy.do_the_thing(True)
 
-    decoy.verify(stub.do_the_thing(True))
+    decoy.verify(spy.do_the_thing(True))
 
     with pytest.raises(AssertionError):
-        decoy.verify(stub.do_the_thing(False))
+        decoy.verify(spy.do_the_thing(False))
 
 
 def test_verify_multiple_calls(decoy: Decoy) -> None:
     """It should be able to verify multiple calls."""
-    stub = decoy.create_decoy(spec=SomeClass)
-    stub_func = decoy.create_decoy_func(spec=some_func)
+    spy = decoy.create_decoy(spec=SomeClass)
+    spy_func = decoy.create_decoy_func(spec=some_func)
 
-    stub.do_the_thing(False)
-    stub.do_the_thing(True)
-    stub_func("hello")
+    spy.do_the_thing(False)
+    spy.do_the_thing(True)
+    spy_func("hello")
 
     decoy.verify(
-        stub.do_the_thing(True),
-        stub_func("hello"),
+        spy.do_the_thing(True),
+        spy_func("hello"),
     )
 
     with pytest.raises(AssertionError) as error_info:
         decoy.verify(
-            stub.do_the_thing(False),
-            stub_func("goodbye"),
+            spy.do_the_thing(False),
+            spy_func("goodbye"),
         )
 
     assert str(error_info.value) == (
@@ -143,8 +143,8 @@ def test_verify_multiple_calls(decoy: Decoy) -> None:
 
     with pytest.raises(AssertionError) as error_info:
         decoy.verify(
-            stub_func("hello"),
-            stub.do_the_thing(True),
+            spy_func("hello"),
+            spy.do_the_thing(True),
         )
 
     assert str(error_info.value) == (
@@ -159,9 +159,9 @@ def test_verify_multiple_calls(decoy: Decoy) -> None:
 
     with pytest.raises(AssertionError) as error_info:
         decoy.verify(
-            stub.do_the_thing(True),
-            stub.do_the_thing(True),
-            stub_func("hello"),
+            spy.do_the_thing(True),
+            spy.do_the_thing(True),
+            spy_func("hello"),
         )
 
     assert str(error_info.value) == (
@@ -174,3 +174,56 @@ def test_verify_multiple_calls(decoy: Decoy) -> None:
         f"2.\tSomeClass.do_the_thing(True){linesep}"
         "3.\tsome_func('hello')"
     )
+
+
+def test_verify_call_count(decoy: Decoy) -> None:
+    """It should be able to verify a specific call count."""
+    spy = decoy.create_decoy_func(spec=some_func)
+
+    spy("hello")
+    spy("hello")
+
+    decoy.verify(spy("hello"))
+    decoy.verify(spy("hello"), times=2)
+    decoy.verify(spy("goodbye"), times=0)
+
+    with pytest.raises(AssertionError) as error_info:
+        decoy.verify(spy("hello"), times=0)
+
+    assert str(error_info.value) == (
+        f"Expected 0 calls:{linesep}"
+        f"1.\tsome_func('hello'){linesep}"
+        f"Found 2 calls:{linesep}"
+        f"1.\tsome_func('hello'){linesep}"
+        "2.\tsome_func('hello')"
+    )
+
+    with pytest.raises(AssertionError) as error_info:
+        decoy.verify(spy("hello"), times=1)
+
+    assert str(error_info.value) == (
+        f"Expected 1 call:{linesep}"
+        f"1.\tsome_func('hello'){linesep}"
+        f"Found 2 calls:{linesep}"
+        f"1.\tsome_func('hello'){linesep}"
+        "2.\tsome_func('hello')"
+    )
+
+    with pytest.raises(AssertionError) as error_info:
+        decoy.verify(spy("hello"), times=3)
+
+    assert str(error_info.value) == (
+        f"Expected 3 calls:{linesep}"
+        f"1.\tsome_func('hello'){linesep}"
+        f"Found 2 calls:{linesep}"
+        f"1.\tsome_func('hello'){linesep}"
+        "2.\tsome_func('hello')"
+    )
+
+
+def test_verify_call_count_raises_multiple_rehearsals(decoy: Decoy) -> None:
+    """It should not be able to verify call count if multiple rehearsals used."""
+    spy = decoy.create_decoy_func(spec=some_func)
+
+    with pytest.raises(ValueError, match="multiple rehearsals"):
+        decoy.verify(spy("hello"), spy("goodbye"), times=1)