Fix some flaky tests and fix a longstanding bug in recursive (#2156)

Fix some flaky tests and fix a longstanding bug in recursive

hypothesis-python/RELEASE.rst

@@ -0,0 +1,6 @@
+RELEASE_TYPE: patch
+
+This release fixes a bug in :func:`~hypothesis.strategies.recursive` which would
+have meant that in practice ``max_leaves`` was treated as if it was lower than
+it actually is - specifically it would be capped at the largest power of two
+smaller than it. It is now handled correctly.

hypothesis-python/src/hypothesis/searchstrategy/recursive.py

@@ -36,6 +36,9 @@ def __init__(self, strategy):
         self.marker = 0
         self.currently_capped = False
 
+    def __repr__(self):
+        return "LimitedStrategy(%r)" % (self.base_strategy,)
+
     def do_validate(self):
         self.base_strategy.validate()
 
@@ -65,7 +68,7 @@ def __init__(self, base, extend, max_leaves):
         self.extend = extend
 
         strategies = [self.limited_base, self.extend(self.limited_base)]
-        while 2 ** len(strategies) <= max_leaves:
+        while 2 ** (len(strategies) - 1) <= max_leaves:
             strategies.append(extend(OneOfStrategy(tuple(strategies))))
         self.strategy = OneOfStrategy(strategies)
 

hypothesis-python/tests/cover/test_recursive.py

@@ -22,7 +22,7 @@
 import hypothesis.strategies as st
 from hypothesis import given
 from hypothesis.errors import InvalidArgument
-from tests.common.debug import minimal
+from tests.common.debug import find_any, minimal
 
 
 @given(st.recursive(st.booleans(), st.lists, max_leaves=10))
@@ -56,6 +56,29 @@ def test_recursive_call_validates_base_is_strategy():
         x.example()
 
 
+def test_can_find_exactly_max_leaves():
+    strat = st.recursive(st.none(), lambda x: st.tuples(x, x), max_leaves=5)
+
+    def enough_leaves(t):
+        print(t)
+        count = 0
+        stack = [t]
+        while stack:
+            s = stack.pop()
+            if s is None:
+                count += 1
+            else:
+                stack.extend(s)
+        return count >= 5
+
+    find_any(strat, enough_leaves)
+
+
+@given(st.recursive(st.none(), lambda x: st.tuples(x, x), max_leaves=1))
+def test_can_exclude_branching_with_max_leaves(t):
+    assert t is None
+
+
 @given(st.recursive(st.none(), lambda x: st.one_of(x, x)))
 def test_issue_1502_regression(s):
     pass

hypothesis-python/tests/cover/test_reproduce_failure.py

@@ -63,6 +63,12 @@ def test_decoding_may_fail(t):
         assert False, "decoding failed with %r, not InvalidArgument" % (e,)
 
 
+def test_invalid_base_64_gives_invalid_argument():
+    with pytest.raises(InvalidArgument) as exc_info:
+        decode_failure(b"/")
+    assert "Invalid base64 encoded" in exc_info.value.args[0]
+
+
 def test_reproduces_the_failure():
     b = b"hello world"
     n = len(b)

hypothesis-python/tests/quality/test_integers.py

@@ -46,10 +46,11 @@ def problems(draw):
             d = ConjectureData.for_buffer(buf)
             k = d.draw(st.integers())
             stop = d.draw_bits(8)
-            if stop > 0 and k > 0:
-                return (draw(st.integers(0, k - 1)), hbytes(d.buffer))
         except (StopTest, IndexError):
             pass
+        else:
+            if stop > 0 and k > 0:
+                return (draw(st.integers(0, k - 1)), hbytes(d.buffer))
 
 
 @example((2, b"\x00\x00\n\x01"))