Add tests for Scenario constructor validation and percentile constraints

Author: Евгений Блинов

tests/documentation/test_readme.py

@@ -3,6 +3,8 @@
 import math
 from functools import partial
 
+import pytest
+
 from microbenchmark import BenchmarkResult, Scenario, ScenarioGroup
 
 
@@ -147,6 +149,71 @@ def test_p99_cached(self) -> None:
         assert result.p99 is result.p99
 
 
+class TestScenarioConstructorValidation:
+    def test_number_zero_raises(self) -> None:
+        # README: "passing 0 or a negative value raises ValueError"
+        with pytest.raises(ValueError):
+            Scenario(lambda: None, name='s', number=0)
+
+    def test_number_negative_raises(self) -> None:
+        with pytest.raises(ValueError):
+            Scenario(lambda: None, name='s', number=-1)
+
+    def test_args_none_and_empty_list_equivalent(self) -> None:
+        # README: "None (the default) and [] both mean the function is called with no arguments"
+        calls_none: list[tuple[object, ...]] = []
+        calls_empty: list[tuple[object, ...]] = []
+
+        def fn_none(*a: object) -> None:
+            calls_none.append(a)
+
+        def fn_empty(*a: object) -> None:
+            calls_empty.append(a)
+
+        Scenario(fn_none, args=None, name='s', number=1).run()
+        Scenario(fn_empty, args=[], name='s', number=1).run()
+        assert calls_none == [()]
+        assert calls_empty == [()]
+
+    def test_args_shallow_copied(self) -> None:
+        # README: "The list is shallow-copied on construction"
+        original = [1, 2]
+        s = Scenario(lambda *_: None, args=original, name='s', number=1)
+        original.append(3)
+        call_log: list[tuple[object, ...]] = []
+
+        def fn(*a: object) -> None:
+            call_log.append(a)
+
+        Scenario(fn, args=[1, 2], name='s', number=1).run()
+        assert call_log == [(1, 2)]  # mutation after construction has no effect
+
+    def test_custom_timer(self) -> None:
+        # README: "Supply a custom clock to get deterministic measurements in tests"
+        tick = [0.0]
+
+        def fake_timer() -> float:
+            tick[0] += 0.001
+            return tick[0]
+
+        result = Scenario(lambda: None, name='s', number=5, timer=fake_timer).run()
+        assert len(result.durations) == 5
+        assert all(d > 0 for d in result.durations)
+
+
+class TestPercentileValidation:
+    def test_percentile_zero_raises(self) -> None:
+        # README: "passing 0 or a value above 100 raises ValueError"
+        result = Scenario(lambda: None, name='noop', number=10).run()
+        with pytest.raises(ValueError):
+            result.percentile(0)
+
+    def test_percentile_above_100_raises(self) -> None:
+        result = Scenario(lambda: None, name='noop', number=10).run()
+        with pytest.raises(ValueError):
+            result.percentile(101)
+
+
 class TestJsonRoundTrip:
     def test_json_round_trip(self) -> None:
         result = Scenario(lambda: None, name='noop', number=100).run()